Question about routing table size on the route reflector


 I am trying to understand the requirements of the route reflector's routing table size. Here is the scenario ;

- internet router is doing multihoming with three different ISPs. It is getting full internet routes from all of them.
- There are 25 PE routers in the topology.

 How can i define the requirement of route reflector's IPv4 and VPNv4 routing table size ? 1 million , 2 million or whatelse ???

Could you help me to understand the logic of this requirement? Kind Regards...

Burak Dikici


  • Routing table is always populated with the best prefixes only, so it doesn't matter whether you have one or fifteen upstream ISPs. You are probably meaning the size of the BGP table? If you have three upstream ISPs, you will receive around 1 million prefixes. Vpnv4 table size depends on how many customer sites e.g. how many prefixes you have for the customers. RR has to be able to house all the prefixes, some of them twice, if customer's are multihomed to two or more PEs.

    Anyway, this is solely a memory requirement. I can't recall how many one ipv4 and/or vpnv4 prefix consumes, but if you multiply the amount with 2 million, you should be fine. So it'll be something like 512MB-1G, I guess.

  • Usually IPv4 and VPNv4 RR pairs used to handle the address families prefixes separately. Some platforms can have scalability issues due to hardware limitations (eg SUP720-3B) that can go up to 256K ipv4 routes, so the h/w that is going to be used for that role should be checked for its capabilities (total ipv4 routes, ipv6 routes, memory, mpls labels, multicast etc). Mainly you have to be aware of CPU and memory in order to handle the number of routes and the number of peer sessions.Platforms like ASR 100x, 76xx, 72xx, can be used for this role. 




  • Platforms like ASR 100x, 76xx, 72xx, can be used for this role. 

    Older 7200 series routers are unable to handle mutli ISP environments now a days as the size of the internet routing table has gone over 300k prefixes.

  • It might be not be the best option in terms of future expansion growths, that would be ASRs for sure but 720xx vxr with NPE-G1/G2 can handle 300k routes in their ipv4 BGP table. Check some route servers eg: telnet or telnet . 




  • yea but with multi ISP implementations you will have x times 300k prefixes. Some 720xs can handle at least 600k, but as you pointed out, it doesn't make much sense to buy one now as it will be obsolete in less than a year :)h

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