Loopback IP masking - 32 or 24 bits? or? [7:32345]
Hi, all; I recently started considering why I might want to have a 32-bit mask for my loopbacks as opposed to some other scheme - for instance using the regularly documented 24-bit mask on a loopback. I am speaking of course, of: Interface Loopback0 IP Address 10.0.0.1 255.255.255.0 versus approaching this matter in this fashion: Interface Loopback0 IP Address 10.0.0.1 255.255.255.255 So, my questions are: 1) Has any one here seen a detailed discussion of this matter? Can you provide me a link to it? 2) Based on what a friend of mine feels, his view is that there is never any benefit to having a 24-bit, or 28, or 29-bit mask on a loopback. In his view, loopbacks will always need to be, very logically, used with 32-bit masks. Can anyone please shed some light on this matter? Thank you. Joshua Dughi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32345&t=32345 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Loopback IP masking - 32 or 24 bits? or? [7:32345]
Your friend is right. Why would you use anything other than a /32 bit mask on a virtual interface? You are not going to route using the loopback address are you? Jim Walker Master Network Engineer Partners HealthCare System, Inc. Information Systems / Technical Services & Operations Tel. (617) 732-8803 Fax (617) 264-5130 This e-mail message and any attachments are confidential and may be privileged. If you are not the intended recipient, please notify me immediately by replying to this message and please destroy all copies of this message and attachments. Thank you. -Original Message- From: Joshua Dughi [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 17, 2002 3:23 PM To: [EMAIL PROTECTED] Subject: Loopback IP masking - 32 or 24 bits? or? [7:32345] Hi, all; I recently started considering why I might want to have a 32-bit mask for my loopbacks as opposed to some other scheme - for instance using the regularly documented 24-bit mask on a loopback. I am speaking of course, of: Interface Loopback0 IP Address 10.0.0.1 255.255.255.0 versus approaching this matter in this fashion: Interface Loopback0 IP Address 10.0.0.1 255.255.255.255 So, my questions are: 1) Has any one here seen a detailed discussion of this matter? Can you provide me a link to it? 2) Based on what a friend of mine feels, his view is that there is never any benefit to having a 24-bit, or 28, or 29-bit mask on a loopback. In his view, loopbacks will always need to be, very logically, used with 32-bit masks. Can anyone please shed some light on this matter? Thank you. Joshua Dughi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32346&t=32345 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Loopback IP masking - 32 or 24 bits? or? [7:32345]
outside of lab exercises, one might consider using /24's or other full subnets for purposes of NAT pool addresses. that's about all I can think of. Chuck ""Walker, Jim"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Your friend is right. Why would you use anything other than a /32 bit mask > on a virtual interface? > You are not going to route using the loopback address are you? > > > > Jim Walker > Master Network Engineer > Partners HealthCare System, Inc. > Information Systems / Technical Services & Operations > Tel. (617) 732-8803 > Fax (617) 264-5130 > This e-mail message and any attachments are confidential and may be > privileged. If you are not the intended recipient, please notify me > immediately by replying to this message and please destroy all copies of > this message and attachments. Thank you. > > > > -Original Message- > From: Joshua Dughi [mailto:[EMAIL PROTECTED]] > Sent: Thursday, January 17, 2002 3:23 PM > To: [EMAIL PROTECTED] > Subject: Loopback IP masking - 32 or 24 bits? or? [7:32345] > > > Hi, all; > > I recently started considering why I might want to have a 32-bit mask > for my loopbacks as opposed to some other scheme - for instance using > the regularly documented 24-bit mask on a loopback. > > I am speaking of course, of: Interface Loopback0 > IP Address 10.0.0.1 > 255.255.255.0 > > versus approaching this matter in this fashion: > > Interface Loopback0 > IP Address 10.0.0.1 > 255.255.255.255 > > So, my questions are: 1) > Has any one here seen a detailed discussion of this matter? > Can you provide me a link to it? > >2) Based on what a friend of mine feels, his view is that there > is never any benefit to having a 24-bit, or 28, or 29-bit mask on a > loopback. In his view, loopbacks will always need to be, very logically, > used with 32-bit masks. > > Can anyone please shed some light on this matter? > > Thank you. > > Joshua Dughi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32347&t=32345 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Loopback IP masking - 32 or 24 bits? or? [7:32345]
Well, you could use part of the loopback subnet for a nat pool if your loopback is a public IP address, that is one reason you may want more than a /32 on the interface. Just throwing things out there. -Original Message- From: Walker, Jim [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 17, 2002 3:42 PM To: [EMAIL PROTECTED] Subject: RE: Loopback IP masking - 32 or 24 bits? or? [7:32345] Your friend is right. Why would you use anything other than a /32 bit mask on a virtual interface? You are not going to route using the loopback address are you? Jim Walker Master Network Engineer Partners HealthCare System, Inc. Information Systems / Technical Services & Operations Tel. (617) 732-8803 Fax (617) 264-5130 This e-mail message and any attachments are confidential and may be privileged. If you are not the intended recipient, please notify me immediately by replying to this message and please destroy all copies of this message and attachments. Thank you. -Original Message- From: Joshua Dughi [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 17, 2002 3:23 PM To: [EMAIL PROTECTED] Subject: Loopback IP masking - 32 or 24 bits? or? [7:32345] Hi, all; I recently started considering why I might want to have a 32-bit mask for my loopbacks as opposed to some other scheme - for instance using the regularly documented 24-bit mask on a loopback. I am speaking of course, of: Interface Loopback0 IP Address 10.0.0.1 255.255.255.0 versus approaching this matter in this fashion: Interface Loopback0 IP Address 10.0.0.1 255.255.255.255 So, my questions are: 1) Has any one here seen a detailed discussion of this matter? Can you provide me a link to it? 2) Based on what a friend of mine feels, his view is that there is never any benefit to having a 24-bit, or 28, or 29-bit mask on a loopback. In his view, loopbacks will always need to be, very logically, used with 32-bit masks. Can anyone please shed some light on this matter? Thank you. Joshua Dughi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32355&t=32345 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Loopback IP masking - 32 or 24 bits? or? [7:32345]
you could also do a FLRP or as known in the industry as a Full Loopback Reverse Path -Original Message- From: Lupi, Guy Sent: Thursday, January 17, 2002 4:16 PM To: [EMAIL PROTECTED] Subject: RE: Loopback IP masking - 32 or 24 bits? or? [7:32345] Well, you could use part of the loopback subnet for a nat pool if your loopback is a public IP address, that is one reason you may want more than a /32 on the interface. Just throwing things out there. -Original Message- From: Walker, Jim [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 17, 2002 3:42 PM To: [EMAIL PROTECTED] Subject: RE: Loopback IP masking - 32 or 24 bits? or? [7:32345] Your friend is right. Why would you use anything other than a /32 bit mask on a virtual interface? You are not going to route using the loopback address are you? Jim Walker Master Network Engineer Partners HealthCare System, Inc. Information Systems / Technical Services & Operations Tel. (617) 732-8803 Fax (617) 264-5130 This e-mail message and any attachments are confidential and may be privileged. If you are not the intended recipient, please notify me immediately by replying to this message and please destroy all copies of this message and attachments. Thank you. -Original Message- From: Joshua Dughi [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 17, 2002 3:23 PM To: [EMAIL PROTECTED] Subject: Loopback IP masking - 32 or 24 bits? or? [7:32345] Hi, all; I recently started considering why I might want to have a 32-bit mask for my loopbacks as opposed to some other scheme - for instance using the regularly documented 24-bit mask on a loopback. I am speaking of course, of: Interface Loopback0 IP Address 10.0.0.1 255.255.255.0 versus approaching this matter in this fashion: Interface Loopback0 IP Address 10.0.0.1 255.255.255.255 So, my questions are: 1) Has any one here seen a detailed discussion of this matter? Can you provide me a link to it? 2) Based on what a friend of mine feels, his view is that there is never any benefit to having a 24-bit, or 28, or 29-bit mask on a loopback. In his view, loopbacks will always need to be, very logically, used with 32-bit masks. Can anyone please shed some light on this matter? Thank you. Joshua Dughi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32364&t=32345 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Loopback IP masking - 32 or 24 bits? or? [7:32345]
I've seen ISP's assign /24's and /25's to loopbacks on dial boxes in order to get the dial pools into the IGP. This is versus static routing them and pushing them into the IGP via redistribution (into NSSA OSPF or ISIS areas). I'm not pro either approach and prefer direct injects to BGP, but I've seen it and it does work. Keep in mind in ospf, you must set the network type to point-to-point (and have an IOS that lets you do that) Pete At 03:51 PM 1/17/2002 -0500, Chuck Larrieu wrote: >outside of lab exercises, one might consider using /24's or other full >subnets for purposes of NAT pool addresses. > >that's about all I can think of. > >Chuck > >""Walker, Jim"" wrote in message >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Your friend is right. Why would you use anything other than a /32 bit mask > > on a virtual interface? > > You are not going to route using the loopback address are you? > > > > > > > > Jim Walker > > Master Network Engineer > > Partners HealthCare System, Inc. > > Information Systems / Technical Services & Operations > > Tel. (617) 732-8803 > > Fax (617) 264-5130 > > This e-mail message and any attachments are confidential and may be > > privileged. If you are not the intended recipient, please notify me > > immediately by replying to this message and please destroy all copies of > > this message and attachments. Thank you. > > > > > > > > -Original Message- > > From: Joshua Dughi [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, January 17, 2002 3:23 PM > > To: [EMAIL PROTECTED] > > Subject: Loopback IP masking - 32 or 24 bits? or? [7:32345] > > > > > > Hi, all; > > > > I recently started considering why I might want to have a 32-bit mask > > for my loopbacks as opposed to some other scheme - for instance using > > the regularly documented 24-bit mask on a loopback. > > > > I am speaking of course, of: Interface Loopback0 > > IP Address 10.0.0.1 > > 255.255.255.0 > > > > versus approaching this matter in this fashion: > > > > Interface Loopback0 > > IP Address 10.0.0.1 > > 255.255.255.255 > > > > So, my questions are: 1) > > Has any one here seen a detailed discussion of this matter? > > Can you provide me a link to it? > > > >2) Based on what a friend of mine feels, his view is that there > > is never any benefit to having a 24-bit, or 28, or 29-bit mask on a > > loopback. In his view, loopbacks will always need to be, very logically, > > used with 32-bit masks. > > > > Can anyone please shed some light on this matter? > > > > Thank you. > > > > Joshua Dughi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32367&t=32345 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Loopback IP masking - 32 or 24 bits? or? [7:32345]
If you are using a classful routing protocol and advertising the Loopback, it's going to burn the /24 anyway, you could use it. -Eh -Original Message- From: Lupi, Guy [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 17, 2002 4:16 PM To: [EMAIL PROTECTED] Subject: RE: Loopback IP masking - 32 or 24 bits? or? [7:32345] Well, you could use part of the loopback subnet for a nat pool if your loopback is a public IP address, that is one reason you may want more than a /32 on the interface. Just throwing things out there. -Original Message- From: Walker, Jim [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 17, 2002 3:42 PM To: [EMAIL PROTECTED] Subject: RE: Loopback IP masking - 32 or 24 bits? or? [7:32345] Your friend is right. Why would you use anything other than a /32 bit mask on a virtual interface? You are not going to route using the loopback address are you? Jim Walker Master Network Engineer Partners HealthCare System, Inc. Information Systems / Technical Services & Operations Tel. (617) 732-8803 Fax (617) 264-5130 This e-mail message and any attachments are confidential and may be privileged. If you are not the intended recipient, please notify me immediately by replying to this message and please destroy all copies of this message and attachments. Thank you. -Original Message- From: Joshua Dughi [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 17, 2002 3:23 PM To: [EMAIL PROTECTED] Subject: Loopback IP masking - 32 or 24 bits? or? [7:32345] Hi, all; I recently started considering why I might want to have a 32-bit mask for my loopbacks as opposed to some other scheme - for instance using the regularly documented 24-bit mask on a loopback. I am speaking of course, of: Interface Loopback0 IP Address 10.0.0.1 255.255.255.0 versus approaching this matter in this fashion: Interface Loopback0 IP Address 10.0.0.1 255.255.255.255 So, my questions are: 1) Has any one here seen a detailed discussion of this matter? Can you provide me a link to it? 2) Based on what a friend of mine feels, his view is that there is never any benefit to having a 24-bit, or 28, or 29-bit mask on a loopback. In his view, loopbacks will always need to be, very logically, used with 32-bit masks. Can anyone please shed some light on this matter? Thank you. Joshua Dughi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32372&t=32345 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
