Re: what is loopback interface for ? [7:9493]
I can simply use the quote from Michael Williams' message above to answer your question... 1. A loopback is a logical interface that never goes down. It's used for various reasons (for setting up various kinds of tunnels, for setting who is the DR/BDR in OSPF, etc). 2. Many people use the subnet mask 255.255.255.255 because that's the only way to assign a single IP to the lookback instead of using more than 1 IP address. Therefore, you normally won't see /24s on loopback interfaces. Richard Sim, CT (Chee Tong) wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I have seems some routers with many lookback interfaces configured. May I know what is the purpose to have so many lookback? I thought one loopback can help us to troubleshoot the connectivity Besides, I am interested about question 5 from Richard, you said the lookback IPs within same network can be configured on different router. Does it mean that if we configured many lookback interfaces, those IPs must be in different network. for example 192.168.101.101/24 192.168.102.102/24. But Any one know what is the reason?? 5) If I configured A's loopback IP to be 192.168.0.1/24, can we still configured B's loopback to be 192.168.0.2/24? Note: there are in same network. Sure you can since they are in two different routers. I won't recommend doing this though... The point is, there is no magic behind a loopback interface as you still need physical interface and routing entries if you need access. Richard -Original Message- From: Richard Chang [mailto:[EMAIL PROTECTED]] Sent: Thursday, June 28, 2001 1:51 AM To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] See lines below. Susan Stone wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Hi.. Sorry, I need a few more questions to verify whether my understanding on loopback is correct or not? Pls answer it. 1) If I have two router A (loopback=192.168.0.1/32) and B (loopback192.168.0.2/32), Router A's S1 int 100.100.100.1/24 is connected to Router B's S1 100.100.100.2/24. There are no more other connection. If S1 of B is down. Can I still telnet from A to B using B's loopback address. No. 2) If Router A and B have another connection. Router A's S2 int 100.200.100.1/24 is connected to Router B's S2 100.200.100.2/24. If S1 of B is down. Can I still telnet from A to B using B's loopback address? Yes, if you have correct routing entries. 3) If Router A doesn't have loopback int configured. Can we still telnet from A to B? Of course you can simply telnet into any physical interface that's still up. 4) Whether the loopback IP address need to be in order or same network? Let say Router A's loopback is 192.168.0.1/32 and Router B's loopback is 20.20.20.1/8. Can we still telnet from A to B? Again, yes, if you have correct routing entries. 5) If I configured A's loopback IP to be 192.168.0.1/24, can we still configured B's loopback to be 192.168.0.2/24? Note: there are in same network. Sure you can since they are in two different routers. I won't recommend doing this though... The point is, there is no magic behind a loopback interface as you still need physical interface and routing entries if you need access. Richard _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. == De informatie opgenomen in dit bericht kan vertrouwelijk zijn en is uitsluitend bestemd voor de geadresseerde. Indien u dit bericht onterecht ontvangt wordt u verzocht de inhoud niet te gebruiken en de afzender direct te informeren door het bericht te retourneren. == The information contained in this message may be confidential and is intended to be exclusively for the addressee. Should you receive this message unintentionally, please do not use the contents herein and notify the sender immediately by return e-mail. == Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=10422t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what is loopback interface for ? [7:9493]
I have seems some routers with many lookback interfaces configured. May I know what is the purpose to have so many lookback? I thought one loopback can help us to troubleshoot the connectivity Besides, I am interested about question 5 from Richard, you said the lookback IPs within same network can be configured on different router. Does it mean that if we configured many lookback interfaces, those IPs must be in different network. for example 192.168.101.101/24 192.168.102.102/24. But Any one know what is the reason?? 5) If I configured A's loopback IP to be 192.168.0.1/24, can we still configured B's loopback to be 192.168.0.2/24? Note: there are in same network. Sure you can since they are in two different routers. I won't recommend doing this though... The point is, there is no magic behind a loopback interface as you still need physical interface and routing entries if you need access. Richard -Original Message- From: Richard Chang [mailto:[EMAIL PROTECTED]] Sent: Thursday, June 28, 2001 1:51 AM To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] See lines below. Susan Stone wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Hi.. Sorry, I need a few more questions to verify whether my understanding on loopback is correct or not? Pls answer it. 1) If I have two router A (loopback=192.168.0.1/32) and B (loopback192.168.0.2/32), Router A's S1 int 100.100.100.1/24 is connected to Router B's S1 100.100.100.2/24. There are no more other connection. If S1 of B is down. Can I still telnet from A to B using B's loopback address. No. 2) If Router A and B have another connection. Router A's S2 int 100.200.100.1/24 is connected to Router B's S2 100.200.100.2/24. If S1 of B is down. Can I still telnet from A to B using B's loopback address? Yes, if you have correct routing entries. 3) If Router A doesn't have loopback int configured. Can we still telnet from A to B? Of course you can simply telnet into any physical interface that's still up. 4) Whether the loopback IP address need to be in order or same network? Let say Router A's loopback is 192.168.0.1/32 and Router B's loopback is 20.20.20.1/8. Can we still telnet from A to B? Again, yes, if you have correct routing entries. 5) If I configured A's loopback IP to be 192.168.0.1/24, can we still configured B's loopback to be 192.168.0.2/24? Note: there are in same network. Sure you can since they are in two different routers. I won't recommend doing this though... The point is, there is no magic behind a loopback interface as you still need physical interface and routing entries if you need access. Richard _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. == De informatie opgenomen in dit bericht kan vertrouwelijk zijn en is uitsluitend bestemd voor de geadresseerde. Indien u dit bericht onterecht ontvangt wordt u verzocht de inhoud niet te gebruiken en de afzender direct te informeren door het bericht te retourneren. == The information contained in this message may be confidential and is intended to be exclusively for the addressee. Should you receive this message unintentionally, please do not use the contents herein and notify the sender immediately by return e-mail. == Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=10361t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
Hi.. Sorry, I need a few more questions to verify whether my understanding on loopback is correct or not? Pls answer it. 1) If I have two router A (loopback=192.168.0.1/32) and B (loopback192.168.0.2/32), Router A's S1 int 100.100.100.1/24 is connected to Router B's S1 100.100.100.2/24. There are no more other connection. If S1 of B is down. Can I still telnet from A to B using B's loopback address. 2) If Router A and B have another connection. Router A's S2 int 100.200.100.1/24 is connected to Router B's S2 100.200.100.2/24. If S1 of B is down. Can I still telnet from A to B using B's loopback address? 3) If Router A doesn't have loopback int configured. Can we still telnet from A to B? 4) Whether the loopback IP address need to be in order or same network? Let say Router A's loopback is 192.168.0.1/32 and Router B's loopback is 20.20.20.1/8. Can we still telnet from A to B? 5) If I configured A's loopback IP to be 192.168.0.1/24, can we still configured B's loopback to be 192.168.0.2/24? Note: there are in same network. _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=10080t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
See lines below. Susan Stone wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Hi.. Sorry, I need a few more questions to verify whether my understanding on loopback is correct or not? Pls answer it. 1) If I have two router A (loopback=192.168.0.1/32) and B (loopback192.168.0.2/32), Router A's S1 int 100.100.100.1/24 is connected to Router B's S1 100.100.100.2/24. There are no more other connection. If S1 of B is down. Can I still telnet from A to B using B's loopback address. No. 2) If Router A and B have another connection. Router A's S2 int 100.200.100.1/24 is connected to Router B's S2 100.200.100.2/24. If S1 of B is down. Can I still telnet from A to B using B's loopback address? Yes, if you have correct routing entries. 3) If Router A doesn't have loopback int configured. Can we still telnet from A to B? Of course you can simply telnet into any physical interface that's still up. 4) Whether the loopback IP address need to be in order or same network? Let say Router A's loopback is 192.168.0.1/32 and Router B's loopback is 20.20.20.1/8. Can we still telnet from A to B? Again, yes, if you have correct routing entries. 5) If I configured A's loopback IP to be 192.168.0.1/24, can we still configured B's loopback to be 192.168.0.2/24? Note: there are in same network. Sure you can since they are in two different routers. I won't recommend doing this though... The point is, there is no magic behind a loopback interface as you still need physical interface and routing entries if you need access. Richard _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=10120t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
what is loopback interface for ? [7:9493]
Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9493t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
A loopback is a logical interface that never goes down. It's used for various reasons (for setting up various kinds of tunnels, for setting who is the DR/BDR in OSPF, etc). It can be set to any valid IP in your network, not just private. Many people use the subnet mask 255.255.255.255 because that's the only way to assign a single IP to the lookback instead of using more than 1 IP address. Mike W. Susan Stone wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9498t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9531t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
Sorry, Just a correction: the mask usually used for a loopback intf is /32 (255.255.255.255) and not /24 (255.255.255.0). Rgards, ER CCNA - Original Message - From: Ednilson Rosa To: Sent: Friday, June 22, 2001 1:20 PM Subject: Re: what is loopback interface for ? [7:9493] A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9542t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
Sue, In addition to what ER had to say, the main purpose of loopback address is actually contained in your question.loopback interface is always up/up, and this helps you to possibly get into the router when there is problem and all interfaces fail, now you can see what is going on and troubleshoot after you have telneted into the router inno/ccnp --- Ednilson Rosa wrote: Sorry, Just a correction: the mask usually used for a loopback intf is /32 (255.255.255.255) and not /24 (255.255.255.0). Rgards, ER CCNA - Original Message - From: Ednilson Rosa To: Sent: Friday, June 22, 2001 1:20 PM Subject: Re: what is loopback interface for ? [7:9493] A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. [EMAIL PROTECTED] __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail http://personal.mail.yahoo.com/ Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9552t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what is loopback interface for ? [7:9493]
Looback interface is a logical interface on your router such that when your router interface(s) goes down your loopback interface still stays up up. the subnet mask normally assigned is 255.255.255.0 not 255.255.255.255 and this is done so that only one Ip address can be assigned to the loobak interface. It's normally used is ospf networks to configure your router(s) as designated or backup designated router(s). Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9553t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
Can you explain to me how you can telnet into the router if all interfaces fail with the exception of the loopback interface? If ALL interfaces fail, the only way you can get to the router is via console or AUX. And you call yourself a CCNP. No wonder the value of Cisco certification value (with the exception of the CCIE) is becoming less desirable these days. Kevin Juniper Network Certified Internet Expert (JNCIE) Qwest Communiations From: Inno. Ama Reply-To: Inno. Ama To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] Date: Fri, 22 Jun 2001 14:57:53 -0400 Sue, In addition to what ER had to say, the main purpose of loopback address is actually contained in your question.loopback interface is always up/up, and this helps you to possibly get into the router when there is problem and all interfaces fail, now you can see what is going on and troubleshoot after you have telneted into the router inno/ccnp --- Ednilson Rosa wrote: Sorry, Just a correction: the mask usually used for a loopback intf is /32 (255.255.255.255) and not /24 (255.255.255.0). Rgards, ER CCNA - Original Message - From: Ednilson Rosa To: Sent: Friday, June 22, 2001 1:20 PM Subject: Re: what is loopback interface for ? [7:9493] A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. [EMAIL PROTECTED] __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9555t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
The last mail I read before my response was about a sarcastic remark from somebody on this list, somebody actually took this up with his boss because he had a signature just like Kevin. My question is, is this what this board has come to? Ok, lets ignorantly agree that you are right, is this the best way to put it across to me? I believe you are a great engineer for Quest and that you are a juniper expert, could this be the difference between cisco and juniper boxes? I have learnt alot from this group, I will not allow you to change my perception of the well cultured members of this group. --- kevin jones wrote: Can you explain to me how you can telnet into the router if all interfaces fail with the exception of the loopback interface?nbsp; If ALL interfaces fail, the only way you can get to the router is via console or AUX.nbsp; And you call yourself a CCNP.nbsp; No wonder the value of Cisco certification value (with the exception of the CCIE) is becoming less desirable these days. Kevin Juniper Network Certified Internet Expert (JNCIE) Qwest Communiations nbsp; gt;From: Inno. Ama gt;Reply-To: Inno. Ama gt;To: [EMAIL PROTECTED] gt;Subject: Re: what is loopback interface for ? [7:9493] gt;Date: Fri, 22 Jun 2001 14:57:53 -0400 gt; gt;Sue, gt; gt;In addition to what ER had to say, the main purpose of gt;loopback address is actually contained in your gt;question.loopback interface is always up/up, and gt;this helps you to possibly get into the router when gt;there is problem and all interfaces fail, now you can gt;see what is going on and troubleshoot after you have gt;telneted into the router gt; gt;inno/ccnp gt;--- Ednilson Rosa wrote: gt; gt; Sorry, gt; gt; gt; gt; Just a correction: the mask usually used for a gt; gt; loopback intf is /32 gt; gt; (255.255.255.255) and not /24 (255.255.255.0). gt; gt; gt; gt; Rgards, gt; gt; gt; gt; ER gt; gt; CCNA gt; gt; gt; gt; - Original Message - gt; gt; From: Ednilson Rosa gt; gt; To: gt; gt; Sent: Friday, June 22, 2001 1:20 PM gt; gt; Subject: Re: what is loopback interface for ? gt; gt; [7:9493] gt; gt; gt; gt; gt; gt; A loopback interface may be used for many purposes. gt; gt; You may use it as the gt; gt; end of a tunnel on a VPN configuration or you may gt; gt; configure it just to have gt; gt; a stable router-id for OSPF, for instance. gt; gt; gt; gt; You don't need to configure it. They are optional gt; gt; and you may use any gt; gt; address you want. If loopback intfs are following a gt; gt; specific address scheme gt; gt; in your network, then they must be planned for some gt; gt; specific function by who gt; gt; designed the network. You should not change it gt; gt; before knowing what function gt; gt; is this (what may be achieved by analyzing your gt; gt; configuration carefully). gt; gt; gt; gt; The subnet mask used on a loopback intf isn't also gt; gt; necessarily /24. This is gt; gt; frequently used though, to economize address space, gt; gt; since you don't need to gt; gt; differentiate network and host on this segment. In gt; gt; this case, host and gt; gt; network are the same and routing is performed with gt; gt; no problem. gt; gt; gt; gt; ER gt; gt; CCNA gt; gt; gt; gt; - Original Message - gt; gt; From: Susan Stone gt; gt; To: gt; gt; Sent: Friday, June 22, 2001 7:22 AM gt; gt; Subject: what is loopback interface for ? [7:9493] gt; gt; gt; gt; gt; gt; Hi, gt; gt; gt; gt; I always wonder what is loopback interface for? Can gt; gt; anyone explained its gt; gt; function? Can we don't configure the loopback gt; gt; interface. Our WAN Lookback gt; gt; always start with 192.168.X.X why? Must we use gt; gt; private IP? I found I can gt; gt; telnet to a remote router using its loopback IP. gt; gt; But I wonder How I route gt; gt; as it always have the subnet mask of gt; gt; 255.255.255.255. Then which is the gt; gt; network and which the host gt; gt; gt; gt; Susan gt; gt; gt;_ gt; gt; Get Your Private, Free E-mail from MSN Hotmail at gt; gt; http://www.hotmail.com. gt;[EMAIL PROTECTED] gt; gt; gt;__ gt;Do You Yahoo!? gt;Get personalized email addresses from Yahoo! Mail gt;http://personal.mail.yahoo.com/ gt; gt; gt; gt; gt;FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html gt;Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get your FREE download of MSN Explorer at http://explorer.msn.com __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail http://personal.mail.yahoo.com/ Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9570t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: what is loopback interface for ? [7:9493]
Nope. 255.255.255.0 (/24) is the standard class C mask. It allows 254 host addresses instead of just one. By using this mask you will be wasting your address space. If IP address availability is not an issue to you then go ahead. Otherwise it's better to use a /32 (255.255.255.255) mask which only permits one single address. ER CCNA - Original Message - From: FELIX KISSIEDU To: Sent: Friday, June 22, 2001 4:21 PM Subject: RE: what is loopback interface for ? [7:9493] Looback interface is a logical interface on your router such that when your router interface(s) goes down your loopback interface still stays up up. the subnet mask normally assigned is 255.255.255.0 not 255.255.255.255 and this is done so that only one Ip address can be assigned to the loobak interface. It's normally used is ospf networks to configure your router(s) as designated or backup designated router(s). Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9577t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
I don't understand your statement the subnet mask normally assigned is 255.255.255.0 not 255.255.255.255 and this is done so that only one Ip address can be assigned to the loobak interface.Using the subnet mask 255.255.255.0 will waste IP addresses. You would use the 255.255.255.255 subnet mask to make it so it only uses 1 IP address. Although the loopback can be used to sway the DR/BDR election, it's also used as endpoints in DLSw, STUN and BSTUN tunnels as well as for administrative purposes as a way to reach a router no matter which particular interface is up or down. Also they are commonly used as a source of an IP address for IP unnumbered interfaces, since they never go down. Mike W. FELIX KISSIEDU wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Looback interface is a logical interface on your router such that when your router interface(s) goes down your loopback interface still stays up up. the subnet mask normally assigned is 255.255.255.0 not 255.255.255.255 and this is done so that only one Ip address can be assigned to the loobak interface. It's normally used is ospf networks to configure your router(s) as designated or backup designated router(s). Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9581t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
I had this huge post typed out ready to flame you for your response, but I don't want to lower myself to that level. I would hope that you are not an indication of the quality of people that Qwest hires. What an ass! Mike W. kevin jones wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Can you explain to me how you can telnet into the router if all interfaces fail with the exception of the loopback interface? If ALL interfaces fail, the only way you can get to the router is via console or AUX. And you call yourself a CCNP. No wonder the value of Cisco certification value (with the exception of the CCIE) is becoming less desirable these days. Kevin Juniper Network Certified Internet Expert (JNCIE) Qwest Communiations From: Inno. Ama Reply-To: Inno. Ama To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] Date: Fri, 22 Jun 2001 14:57:53 -0400 Sue, In addition to what ER had to say, the main purpose of loopback address is actually contained in your question.loopback interface is always up/up, and this helps you to possibly get into the router when there is problem and all interfaces fail, now you can see what is going on and troubleshoot after you have telneted into the router inno/ccnp --- Ednilson Rosa wrote: Sorry, Just a correction: the mask usually used for a loopback intf is /32 (255.255.255.255) and not /24 (255.255.255.0). Rgards, ER CCNA - Original Message - From: Ednilson Rosa To: Sent: Friday, June 22, 2001 1:20 PM Subject: Re: what is loopback interface for ? [7:9493] A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. [EMAIL PROTECTED] __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9584t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what is loopback interface for ? [7:9493]
I wouldn't worry too muchHe's got enough trouble trying to find employment with that Juniper Certification! Haha! -Original Message- From: Michael L. Williams [mailto:[EMAIL PROTECTED]] Sent: Friday, June 22, 2001 6:43 PM To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] I had this huge post typed out ready to flame you for your response, but I don't want to lower myself to that level. I would hope that you are not an indication of the quality of people that Qwest hires. What an ass! Mike W. kevin jones wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Can you explain to me how you can telnet into the router if all interfaces fail with the exception of the loopback interface? If ALL interfaces fail, the only way you can get to the router is via console or AUX. And you call yourself a CCNP. No wonder the value of Cisco certification value (with the exception of the CCIE) is becoming less desirable these days. Kevin Juniper Network Certified Internet Expert (JNCIE) Qwest Communiations From: Inno. Ama Reply-To: Inno. Ama To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] Date: Fri, 22 Jun 2001 14:57:53 -0400 Sue, In addition to what ER had to say, the main purpose of loopback address is actually contained in your question.loopback interface is always up/up, and this helps you to possibly get into the router when there is problem and all interfaces fail, now you can see what is going on and troubleshoot after you have telneted into the router inno/ccnp --- Ednilson Rosa wrote: Sorry, Just a correction: the mask usually used for a loopback intf is /32 (255.255.255.255) and not /24 (255.255.255.0). Rgards, ER CCNA - Original Message - From: Ednilson Rosa To: Sent: Friday, June 22, 2001 1:20 PM Subject: Re: what is loopback interface for ? [7:9493] A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. [EMAIL PROTECTED] __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9589t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
Kevin, I believe what was being sted was that in a router with multiple ints, if some go down and some go up, routing info can still be exchanged. It is often the neighbor specified in a bgp config. Brian Sonic Whalen Success = Preparation + Opportunity On Fri, 22 Jun 2001, kevin jones wrote: Can you explain to me how you can telnet into the router if all interfaces fail with the exception of the loopback interface? If ALL interfaces fail, the only way you can get to the router is via console or AUX. And you call yourself a CCNP. No wonder the value of Cisco certification value (with the exception of the CCIE) is becoming less desirable these days. Kevin Juniper Network Certified Internet Expert (JNCIE) Qwest Communiations From: Inno. Ama Reply-To: Inno. Ama To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] Date: Fri, 22 Jun 2001 14:57:53 -0400 Sue, In addition to what ER had to say, the main purpose of loopback address is actually contained in your question.loopback interface is always up/up, and this helps you to possibly get into the router when there is problem and all interfaces fail, now you can see what is going on and troubleshoot after you have telneted into the router inno/ccnp --- Ednilson Rosa wrote: Sorry, Just a correction: the mask usually used for a loopback intf is /32 (255.255.255.255) and not /24 (255.255.255.0). Rgards, ER CCNA - Original Message - From: Ednilson Rosa To: Sent: Friday, June 22, 2001 1:20 PM Subject: Re: what is loopback interface for ? [7:9493] A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. [EMAIL PROTECTED] __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9598t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
Did you guys read what happened to me when i freaked at someone like that? Take a look at the thread how to track down unused ports on a switch and then stop ripping on people who flame you for saying something stupid. or. stop saying stupid things. or just keep your mouth shut if you cant say anything useful. BTW, d0rk, i can establish an IP connection to the AUX interface via the AUX interface/PPP. isnt that an interface? if all the interfaces fail that wouldnt work either. stop being dicks. Love, Peter Slow. To: Sent: Friday, June 22, 2001 6:42 PM Subject: Re: what is loopback interface for ? [7:9493] I had this huge post typed out ready to flame you for your response, but I don't want to lower myself to that level. I would hope that you are not an indication of the quality of people that Qwest hires. What an ass! Mike W. kevin jones wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Can you explain to me how you can telnet into the router if all interfaces fail with the exception of the loopback interface? If ALL interfaces fail, the only way you can get to the router is via console or AUX. And you call yourself a CCNP. No wonder the value of Cisco certification value (with the exception of the CCIE) is becoming less desirable these days. Kevin Juniper Network Certified Internet Expert (JNCIE) Qwest Communiations From: Inno. Ama Reply-To: Inno. Ama To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] Date: Fri, 22 Jun 2001 14:57:53 -0400 Sue, In addition to what ER had to say, the main purpose of loopback address is actually contained in your question.loopback interface is always up/up, and this helps you to possibly get into the router when there is problem and all interfaces fail, now you can see what is going on and troubleshoot after you have telneted into the router inno/ccnp --- Ednilson Rosa wrote: Sorry, Just a correction: the mask usually used for a loopback intf is /32 (255.255.255.255) and not /24 (255.255.255.0). Rgards, ER CCNA - Original Message - From: Ednilson Rosa To: Sent: Friday, June 22, 2001 1:20 PM Subject: Re: what is loopback interface for ? [7:9493] A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. [EMAIL PROTECTED] __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9600t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what is loopback interface for ? [7:9493]
People who send flames or retorts to flames are just like people who blow themselves up in terrorist attacks: they think they're getting revenge, when really they're the cause of the problem. If it ain't Cisco-related, keep it private. 'Nuff said. - Original Message - From: Peter I. Slow To: [EMAIL PROTECTED] Sent: Friday, June 22, 2001 10:03 PM Subject: Re: what is loopback interface for ? [7:9493] Did you guys read what happened to me when i freaked at someone like that? Take a look at the thread how to track down unused ports on a switch and then stop ripping on people who flame you for saying something stupid. or. stop saying stupid things. or just keep your mouth shut if you cant say anything useful. BTW, d0rk, i can establish an IP connection to the AUX interface via the AUX interface/PPP. isnt that an interface? if all the interfaces fail that wouldnt work either. stop being dicks. Love, Peter Slow. To: Sent: Friday, June 22, 2001 6:42 PM Subject: Re: what is loopback interface for ? [7:9493] I had this huge post typed out ready to flame you for your response, but I don't want to lower myself to that level. I would hope that you are not an indication of the quality of people that Qwest hires. What an ass! Mike W. kevin jones wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Can you explain to me how you can telnet into the router if all interfaces fail with the exception of the loopback interface? If ALL interfaces fail, the only way you can get to the router is via console or AUX. And you call yourself a CCNP. No wonder the value of Cisco certification value (with the exception of the CCIE) is becoming less desirable these days. Kevin Juniper Network Certified Internet Expert (JNCIE) Qwest Communiations From: Inno. Ama Reply-To: Inno. Ama To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] Date: Fri, 22 Jun 2001 14:57:53 -0400 Sue, In addition to what ER had to say, the main purpose of loopback address is actually contained in your question.loopback interface is always up/up, and this helps you to possibly get into the router when there is problem and all interfaces fail, now you can see what is going on and troubleshoot after you have telneted into the router inno/ccnp --- Ednilson Rosa wrote: Sorry, Just a correction: the mask usually used for a loopback intf is /32 (255.255.255.255) and not /24 (255.255.255.0). Rgards, ER CCNA - Original Message - From: Ednilson Rosa To: Sent: Friday, June 22, 2001 1:20 PM Subject: Re: what is loopback interface for ? [7:9493] A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. [EMAIL PROTECTED] __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9602t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report mi
Re: what is loopback interface for ? [7:9493]
I'm not really wanting to get into the sarcasm part of this thread but I am wondering about the JNCIE. I recently got email from a Juniper guy in Canada (who works for Juniper Canada) and he signed it JNCIE #0005 (or maybe 0015), in any event a very very low number. I showed the email to a few buddies thinking that it would be cool to have such a low number. I just thought that anybody with that cert, who would use it in his email signature - would quote his number just like the CCIE. just an off topic type of thought Kevin Wigle - Original Message - From: CiscoG To: Sent: Friday, 22 June, 2001 19:16 Subject: RE: what is loopback interface for ? [7:9493] I wouldn't worry too muchHe's got enough trouble trying to find employment with that Juniper Certification! Haha! -Original Message- From: Michael L. Williams [mailto:[EMAIL PROTECTED]] Sent: Friday, June 22, 2001 6:43 PM To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] I had this huge post typed out ready to flame you for your response, but I don't want to lower myself to that level. I would hope that you are not an indication of the quality of people that Qwest hires. What an ass! Mike W. kevin jones wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Can you explain to me how you can telnet into the router if all interfaces fail with the exception of the loopback interface? If ALL interfaces fail, the only way you can get to the router is via console or AUX. And you call yourself a CCNP. No wonder the value of Cisco certification value (with the exception of the CCIE) is becoming less desirable these days. Kevin Juniper Network Certified Internet Expert (JNCIE) Qwest Communiations Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9605t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what is loopback interface for ? [7:9493]
dickhead -Original Message- From: kevin jones [mailto:[EMAIL PROTECTED]] Sent: Friday, June 22, 2001 3:47 PM To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] Can you explain to me how you can telnet into the router if all interfaces fail with the exception of the loopback interface? If ALL interfaces fail, the only way you can get to the router is via console or AUX. And you call yourself a CCNP. No wonder the value of Cisco certification value (with the exception of the CCIE) is becoming less desirable these days. Kevin Juniper Network Certified Internet Expert (JNCIE) Qwest Communiations From: Inno. Ama Reply-To: Inno. Ama To: [EMAIL PROTECTED] Subject: Re: what is loopback interface for ? [7:9493] Date: Fri, 22 Jun 2001 14:57:53 -0400 Sue, In addition to what ER had to say, the main purpose of loopback address is actually contained in your question.loopback interface is always up/up, and this helps you to possibly get into the router when there is problem and all interfaces fail, now you can see what is going on and troubleshoot after you have telneted into the router inno/ccnp --- Ednilson Rosa wrote: Sorry, Just a correction: the mask usually used for a loopback intf is /32 (255.255.255.255) and not /24 (255.255.255.0). Rgards, ER CCNA - Original Message - From: Ednilson Rosa To: Sent: Friday, June 22, 2001 1:20 PM Subject: Re: what is loopback interface for ? [7:9493] A loopback interface may be used for many purposes. You may use it as the end of a tunnel on a VPN configuration or you may configure it just to have a stable router-id for OSPF, for instance. You don't need to configure it. They are optional and you may use any address you want. If loopback intfs are following a specific address scheme in your network, then they must be planned for some specific function by who designed the network. You should not change it before knowing what function is this (what may be achieved by analyzing your configuration carefully). The subnet mask used on a loopback intf isn't also necessarily /24. This is frequently used though, to economize address space, since you don't need to differentiate network and host on this segment. In this case, host and network are the same and routing is performed with no problem. ER CCNA - Original Message - From: Susan Stone To: Sent: Friday, June 22, 2001 7:22 AM Subject: what is loopback interface for ? [7:9493] Hi, I always wonder what is loopback interface for? Can anyone explained its function? Can we don't configure the loopback interface. Our WAN Lookback always start with 192.168.X.X why? Must we use private IP? I found I can telnet to a remote router using its loopback IP. But I wonder How I route as it always have the subnet mask of 255.255.255.255. Then which is the network and which the host Susan _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. [EMAIL PROTECTED] __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=9606t=9493 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
