Loopback interface for OSPF [7:4802]
Hi; For OSPF implementation, an area can be configured in the Loopback interface. But what purpose, when should I do it? TIA Vincent Chong Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4802&t=4802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Loopback interface for OSPF [7:4802]
There's not much point in putting the loopbacks in their own area unless you're in a lab scenario and trying to make a bigger, more complicated network. ..At least not that I can think of. However, there is definitely a usefulness for loopback interfaces in OSPF -- use them to set your RIDs (used to indentify the router in OSPF LSA's) to controllable, meaningfull addresses. This doesn't even require that the loopbacks be part of the OSPF domain, just that they be configured and up. Highest loopback IP on the router will be the OSPF RID of any LSA's generated by that router (as shown in commands such as show ip ospf neighbor, etc)... -Brad McConnell ""Vincent Chong"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hi; > > For OSPF implementation, an area can be configured in the Loopback > interface. > But what purpose, when should I do it? > > TIA > Vincent Chong > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4803&t=4802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Loopback interface for OSPF [7:4802]
Brad is very correct on the use of Loopback interface in OSPF. 1. Loopback interface is more stable than any other physical interface. Catch here is OSPF will continue to use a RID learned from a physical interface even if the interface subsequently fails. So nothing great about this advantage. 2. Admin's can assign RID in a more controlled way because RID's can belong to same network/subnet across the entire OSPF domain. This is the main advantage of using Loopback interface in OSPF. Brijesh - Original Message - From: "Brad McConnell" To: Sent: Thursday, May 17, 2001 10:50 AM Subject: Re: Loopback interface for OSPF [7:4802] > There's not much point in putting the loopbacks in their own area unless > you're in a lab scenario and trying to make a bigger, more complicated > network. ..At least not that I can think of. However, there is definitely > a usefulness for loopback interfaces in OSPF -- use them to set your RIDs > (used to indentify the router in OSPF LSA's) to controllable, meaningfull > addresses. This doesn't even require that the loopbacks be part of the OSPF > domain, just that they be configured and up. Highest loopback IP on the > router will be the OSPF RID of any LSA's generated by that router (as shown > in commands such as show ip ospf neighbor, etc)... > > -Brad McConnell > > ""Vincent Chong"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Hi; > > > > For OSPF implementation, an area can be configured in the Loopback > > interface. > > But what purpose, when should I do it? > > > > TIA > > Vincent Chong > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4808&t=4802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Fw: Loopback interface for OSPF [7:4802]
- Original Message - From: "CCNP" To: Sent: Thursday, May 17, 2001 11:19 AM Subject: Re: Loopback interface for OSPF [7:4802] > Brad is very correct on the use of Loopback interface in OSPF. > > 1. Loopback interface is more stable than any other physical interface. > Catch here is OSPF will continue to use a RID learned from a physical > interface even if the interface subsequently fails. So nothing great about > this advantage. > > 2. Admin's can assign RID in a more controlled way because RID's can belong > to same network/subnet across the entire OSPF domain. This is the main > advantage of using Loopback interface in OSPF. > > Brijesh > > - Original Message - > From: "Brad McConnell" > To: > Sent: Thursday, May 17, 2001 10:50 AM > Subject: Re: Loopback interface for OSPF [7:4802] > > > > There's not much point in putting the loopbacks in their own area unless > > you're in a lab scenario and trying to make a bigger, more complicated > > network. ..At least not that I can think of. However, there is > definitely > > a usefulness for loopback interfaces in OSPF -- use them to set your RIDs > > (used to indentify the router in OSPF LSA's) to controllable, meaningfull > > addresses. This doesn't even require that the loopbacks be part of the > OSPF > > domain, just that they be configured and up. Highest loopback IP on the > > router will be the OSPF RID of any LSA's generated by that router (as > shown > > in commands such as show ip ospf neighbor, etc)... > > > > -Brad McConnell > > > > ""Vincent Chong"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Hi; > > > > > > For OSPF implementation, an area can be configured in the Loopback > > > interface. > > > But what purpose, when should I do it? > > > > > > TIA > > > Vincent Chong > > > FAQ, list archives, and subscription info: > > http://www.groupstudy.com/list/cisco.html > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4811&t=4802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Loopback interface for OSPF [7:4802]
By the way, cisco has new command can control the router id under ospf router configuration. router-id x.w.y.z (in ip address format) Vincent Chong ""Brad McConnell"" There's not much point in putting the loopbacks in their own area unless > you're in a lab scenario and trying to make a bigger, more complicated > network. ..At least not that I can think of. However, there is definitely > a usefulness for loopback interfaces in OSPF -- use them to set your RIDs > (used to indentify the router in OSPF LSA's) to controllable, meaningfull > addresses. This doesn't even require that the loopbacks be part of the OSPF > domain, just that they be configured and up. Highest loopback IP on the > router will be the OSPF RID of any LSA's generated by that router (as shown > in commands such as show ip ospf neighbor, etc)... > > -Brad McConnell > > ""Vincent Chong"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Hi; > > > > For OSPF implementation, an area can be configured in the Loopback > > interface. > > But what purpose, when should I do it? > > > > TIA > > Vincent Chong > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4817&t=4802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Loopback interface for OSPF [7:4802]
> Couple off the top of my head: OSPF Area router ID If you're running OSPF as your IGP in a hub/spoke type topology, you'd want BGP sourced on an interface that doesn't have a potential to go down. Phil - Original Message - From: Vincent Chong To: Sent: Thursday, May 17, 2001 1:16 AM Subject: Loopback interface for OSPF [7:4802] > Hi; > > > > TIA > Vincent Chong > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4825&t=4802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Loopback interface for OSPF [7:4802]
At 01:16 AM 5/17/01 -0400, Vincent Chong wrote: >Hi; > > For OSPF implementation, an area can be configured in the Loopback >interface. >But what purpose, when should I do it? > >TIA >Vincent Chong Well, somewhat off topic, but the router id will lock on to the loopback address, which might stabilize the network more. However, I think you even wrote to the list an email about that so that probably is not what you are asking. Now why would you want to advertise a loopback interface using OSPF or any IGP? To teach the IGP how to get their later on for redistribution into BGP. Basically only used if you need to use an AS as a transit AS. You have basically two choices. IBGP (full mesh) to the ASBRs of the transit AS. Or, you can redistribute the "transit route" through an IGP instead. They tend to use loopback interfaces to help the transit ASs achieve more stability to avoid flappage. I am somewhat new on this, so if I am wrong, I will happily defer to someone with more experience, but this is my take on it from what I have read. -Carroll Kong Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4836&t=4802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Loopback interface for OSPF [7:4802]
You're pretty much there. To clarify, transit AS's use only fully meshed IBGP (assuming scalability techniques like Route Reflection and Confederations also in use) and usually peer internally via loopback addresses for stability and as you correctly point out, use the IGP to distribute reachability information for those loopbacks. Using IGP only routers for transit might have worked at some point years ago, but simply doesn't cut it anymore due to the sheer volume of paths in the internet. *** REPLY SEPARATOR *** On 5/17/2001 at 10:04 AM Carroll Kong wrote: >At 01:16 AM 5/17/01 -0400, Vincent Chong wrote: >>Hi; >> >> For OSPF implementation, an area can be configured in the Loopback >>interface. >>But what purpose, when should I do it? >> >>TIA >>Vincent Chong > >Well, somewhat off topic, but the router id will lock on to the loopback >address, which might stabilize the network more. However, I think you >even >wrote to the list an email about that so that probably is not what you are >asking. > >Now why would you want to advertise a loopback interface using OSPF or any >IGP? To teach the IGP how to get their later on for redistribution into >BGP. Basically only used if you need to use an AS as a transit AS. You >have basically two choices. > >IBGP (full mesh) to the ASBRs of the transit AS. Or, you can redistribute >the "transit route" through an IGP instead. They tend to use loopback >interfaces to help the transit ASs achieve more stability to avoid >flappage. I am somewhat new on this, so if I am wrong, I will happily >defer to someone with more experience, but this is my take on it from what >I have read. > > > >-Carroll Kong >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4863&t=4802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Fw: Loopback interface for OSPF [7:4802]
If you want to be able to address the router as a whole (rather than a particular interface), for example for SNMP, telnet, etc, then using a loopback address is a good way to do it.Of course, if you do this, your loopback address needs to be included in OSPF (or whatever routing protocol you're running) so that it is visible throughout your network. JMcL -- Forwarded by Jenny Mcleod/NSO/CSDA on 18/05/2001 09:22 am --- "CCNP" @groupstudy.com on 17/05/2001 04:20:38 pm Please respond to "CCNP" Sent by: [EMAIL PROTECTED] To: [EMAIL PROTECTED] cc: Subject: Fw: Loopback interface for OSPF [7:4802] - Original Message - From: "CCNP" To: Sent: Thursday, May 17, 2001 11:19 AM Subject: Re: Loopback interface for OSPF [7:4802] > Brad is very correct on the use of Loopback interface in OSPF. > > 1. Loopback interface is more stable than any other physical interface. > Catch here is OSPF will continue to use a RID learned from a physical > interface even if the interface subsequently fails. So nothing great about > this advantage. > > 2. Admin's can assign RID in a more controlled way because RID's can belong > to same network/subnet across the entire OSPF domain. This is the main > advantage of using Loopback interface in OSPF. > > Brijesh > > - Original Message - > From: "Brad McConnell" > To: > Sent: Thursday, May 17, 2001 10:50 AM > Subject: Re: Loopback interface for OSPF [7:4802] > > > > There's not much point in putting the loopbacks in their own area unless > > you're in a lab scenario and trying to make a bigger, more complicated > > network. ..At least not that I can think of. However, there is > definitely > > a usefulness for loopback interfaces in OSPF -- use them to set your RIDs > > (used to indentify the router in OSPF LSA's) to controllable, meaningfull > > addresses. This doesn't even require that the loopbacks be part of the > OSPF > > domain, just that they be configured and up. Highest loopback IP on the > > router will be the OSPF RID of any LSA's generated by that router (as > shown > > in commands such as show ip ospf neighbor, etc)... > > > > -Brad McConnell > > > > ""Vincent Chong"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Hi; > > > > > > For OSPF implementation, an area can be configured in the Loopback > > > interface. > > > But what purpose, when should I do it? > > > > > > TIA > > > Vincent Chong > > > FAQ, list archives, and subscription info: > > http://www.groupstudy.com/list/cisco.html > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4928&t=4802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
