Maximum BGP peers supported on ASR 9k, 1k and CNS devices?

[Seth Beauchamp]

I have been looking for numbers regarding maximum simultaneous BGP sessions these devices can handle. Has anyone seen any documents or have any personal experience with high amounts of bgp sessions on any of these devices? Or am I more likely to hit a limit on total number of routes before I would hit a BGP session limit?

[balaji.bandi]

Look the technical document it has the information for your query.

https://www.cisco.com/c/en/us/products/collateral/routers/asr-1000-series-aggregation-services-routers/data_sheet_c78-441072.html

[Seth Beauchamp]

I see it lists the maximum number of routes it can hold, but nothing about how many sessions/neighbors can be established simultaneously. Do you think there is any worry specifically about how many BGP neighbors a single device can handle, regardless of the number of routes?

[balaji.bandi · Accepted solution]

You can have Many peers as long as you have enough route can hold your memory and CPU head room available.

[Giuseppe Larosa]

Hello Seth,

have a look at the following Troubleshooting BGP cisco live session

https://www.ciscolive.com/c/dam/r/ciscolive/us/docs/2017/pdf/BRKRST-3320.pdf

The number of BGP peers can have an impact on devices acting as Route Reflector Servers.

There are some configuration tips for improving the number of BGP peers supported.

One of them is to increase the hold-queue on interfaces that are used for process switched packets like BGP messages are.

Other tools are available to

see slide 50: the number of BGP peers have an impact on update activities

see slide 59: about the issue of dropping TCP Acks on RRS with hundreds of BGP clients.

In the past on other platforms like C7200 there was the SPD concept Selective Packet Discard also on Cisco 12000 with classic IOS.

see for example the following book

http://www.ce.uniroma2.it/~lopresti/Didattica/Biss2010/BGP/BGP_Design_and_Implementation.pdf

This book provides suggestions for building high scalable BGP networks also in regards of number of BGP peers.

There should be some modern equivalent of SPD on modern router platforms.

Hope to help

Giuseppe