RE: what does "peer routers" mean? [7:35705]
There is a meaning common to all routing protocols, and an additional special meaning in BGP. A peer is a router with which you have a direct IP connection. In other words, two BGP routers are peers as long as the BGP connection is between the loopbacks on both routers; there can be intervening IGP routers. Peer implies neighbor, but, in some protocols, has the additional nuance that you exchange routing information with it as well as forward through it. As a rule of thumb, you should not have more than 20-30 iBGP or eBGP peers on a BGP router, unless you know exactly what you are doing and can do the appropriate capacity planning. This is a reasonable rule for IGP routers as well, with the caveat that you can have more static peers than that. The total number of peers are limited by the number of Interface Descriptor Blocks that are available. IDBs are the sum of all logical and physical interfaces, including subinterfaces. For a long time, it was 300, but newer releases allow more. The 50 router limit per OSPF area is conservative, but it doesn't refer to peers, but the total number of OSPF routers in the area. The reason for this is the workload for computing the Dijkstra, in a single area, is proportional to: ((numberOfPrefixes * numberOfPrefixes) * log(numberOfRouters) So the more total routers (i.e., Type 1 LSAs), the more the CPU load goes up. Still, an experienced designer may be able to get hundreds of routers working in an area, although they may need fast CPUs. I wouldn't want to have more than a maximum of 47 OSPF routers on the same segment, since that's the maximum you can fit into a single Hello packet. Someone mentioned limits of peers per AS. Certainly, if that's in the BGP sense, large providers routinely have thousands, perhaps tens of thousands, of routers. They certainly use hierarchy and don't put excessive peers on any given box. -- "What Problem are you trying to solve?" ***send Cisco questions to the list, so all can benefit -- not directly to me*** Howard C. Berkowitz [EMAIL PROTECTED] Chief Technology Officer, GettLab/Gett Communications Technical Director, CertificationZone.com "retired" Certified Cisco Systems Instructor (CID) #93005 Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35817&t=35705 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what does "peer routers" mean? [7:35705]
There is a meaning common to all routing protocols, and an additional special meaning in BGP. A peer is a router with which you have a direct IP connection. In other words, two BGP routers are peers as long as the BGP connection is between the loopbacks on both routers; there can be intervening IGP routers. Peer implies neighbor, but, in some protocols, has the additional nuance that you exchange routing information with it as well as forward through it. As a rule of thumb, you should not have more than 20-30 iBGP or eBGP peers on a BGP router, unless you know exactly what you are doing and can do the appropriate capacity planning. This is a reasonable rule for IGP routers as well, with the caveat that you can have more static peers than that. The total number of peers are limited by the number of Interface Descriptor Blocks that are available. IDBs are the sum of all logical and physical interfaces, including subinterfaces. For a long time, it was 300, but newer releases allow more. The 50 router limit per OSPF area is conservative, but it doesn't refer to peers, but the total number of OSPF routers in the area. The reason for this is the workload for computing the Dijkstra, in a single area, is proportional to: ((numberOfPrefixes * numberOfPrefixes) * log(numberOfRouters) So the more total routers (i.e., Type 1 LSAs), the more the CPU load goes up. Still, an experienced designer may be able to get hundreds of routers working in an area, although they may need fast CPUs. I wouldn't want to have more than a maximum of 47 OSPF routers on the same segment, since that's the maximum you can fit into a single Hello packet. Someone mentioned limits of peers per AS. Certainly, if that's in the BGP sense, large providers routinely have thousands, perhaps tens of thousands, of routers. They certainly use hierarchy and don't put excessive peers on any given box. -- "What Problem are you trying to solve?" ***send Cisco questions to the list, so all can benefit -- not directly to me*** Howard C. Berkowitz [EMAIL PROTECTED] Chief Technology Officer, GettLab/Gett Communications Technical Director, CertificationZone.com "retired" Certified Cisco Systems Instructor (CID) #93005 Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35793&t=35705 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what does "peer routers" mean? [7:35705]
Right, one of the answers had 50 routers per AS for EIGRP. For OSPF, I have heard 50 to 150 per area depending on how they are configured. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35771&t=35705 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what does "peer routers" mean? [7:35705]
The area I was talking about is an OSPF area. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of mlh Sent: Monday, February 18, 2002 11:19 AM To: [EMAIL PROTECTED] Subject: Re: what does "peer routers" mean? [7:35705] George and Tom, Thank you for your answer. Could you give me more detail about "an area"? Is it a subnet or AS? - Original Message - From: "Tom Petzold" To: "mlh" ; Sent: Monday, February 18, 2002 11:01 AM Subject: RE: what does "peer routers" mean? [7:35705] > Peer routers are routers in the same area. > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > mlh > Sent: Sunday, February 17, 2002 11:32 PM > To: [EMAIL PROTECTED] > Subject: what does "peer routers" mean? [7:35705] > > > OSPF and EIGRP could support a maximum of 50 peer routers. > Does it mean only 50 routers using OSPF or EIGRP can connect to the same > subnet? > > Thank you in advance. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35763&t=35705 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what does "peer routers" mean? [7:35705]
FOr eigrp, Peers would be entries in the neighbor table. 50 routers in the same AS would limit the scale of an internetwork. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35748&t=35705 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: what does "peer routers" mean? [7:35705]
George and Tom, Thank you for your answer. Could you give me more detail about "an area"? Is it a subnet or AS? - Original Message - From: "Tom Petzold" To: "mlh" ; Sent: Monday, February 18, 2002 11:01 AM Subject: RE: what does "peer routers" mean? [7:35705] > Peer routers are routers in the same area. > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > mlh > Sent: Sunday, February 17, 2002 11:32 PM > To: [EMAIL PROTECTED] > Subject: what does "peer routers" mean? [7:35705] > > > OSPF and EIGRP could support a maximum of 50 peer routers. > Does it mean only 50 routers using OSPF or EIGRP can connect to the same > subnet? > > Thank you in advance. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35741&t=35705 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what does "peer routers" mean? [7:35705]
Peer routers are routers in the same area. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of mlh Sent: Sunday, February 17, 2002 11:32 PM To: [EMAIL PROTECTED] Subject: what does "peer routers" mean? [7:35705] OSPF and EIGRP could support a maximum of 50 peer routers. Does it mean only 50 routers using OSPF or EIGRP can connect to the same subnet? Thank you in advance. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35740&t=35705 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: what does "peer routers" mean? [7:35705]
AFAIK, in OSPF it means that you should not have more than 50 routers in one area, in EIGRP it means that you should not have more than 50 routers in the same AS. Regards, Georg Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35729&t=35705 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
