[vc_row][vc_column][vc_column_text]There’s the adage “nobody ever got fired for buying IBM”. In the BGP space, nobody ever got fired for buying Cisco or Juniper. They both have robust BGP implementations. Slightly lesser known is Brocade, and there’s also several other makers of BGP routers. Before you buy, make sure that the specific model you want to buy does have the right feature set to run BGP and any other protocols you may need.
Many routers have limitations on how many prefixes they can handle. Currently, a full IPv4 BGP table is about 600,000 prefixes. This is likely to reach a million in 2019. The IPv4 BGP table has been growing at about 16% per year, with no slowdown in recent years even though most regions are out of IPv4 addresses. The IPv6 BGP table is growing faster, but is less than 30,000 prefixes at this time.
| WARNING: A router that can support a million prefixes will probably accommodate a full BGP table until some time in 2019. |
Routers have a BGP RIB (routing information base) and a main routing table / RIB, which are stored in RAM. The BGP RIB holds a copy of all BGP information received from all BGP neighbors, so with two ISPs, the BGP RIB will be 1.2 million entries. The main routing table has one copy of each prefix. Then there’s the FIB (forwarding information base), which is used for actually forwarding the packets. The FIB also has one copy per prefix. So the main routing table and the FIB are 600,000 prefixes each, currently. The RIBs reside in RAM, which is usually not a bottleneck. However, the FIB may have hardware constraints. Some cheap multilayer switches are able to run BGP, but only have 10,000 or so FIB entries. Until recently, routers with a FIB limit of 512,000 prefixes were used. But then the BGP table grew beyond 512,000 prefixes and those routers were no longer very useful.
It’s not strictly necessary to accommodate the full BGP table in your routers, but without having full BGP feeds from each ISP, you’ll have to use a default route to reach certain destinations. If that default route points to ISP A but the destination is only reachable through ISP B, this means that you won’t be able to reach that destination if you don’t have full BGP feeds. However, this is not something that is routinely an issue.
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