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BGP and memory consumption



If anyone can help me with this please:

Generaly speaking, one router R is connected to 2 different ISPs via BGP and receive full BGP table

1) How much memory this router R needs? Does it need to store 2 BGP tables ( 2 x 300.000 routes) plus routing table?

If this is case then this should be approximately 600MB, is this correct?

2) What if router has 4 BGP uplinks on which it receives full BGP table? Does this mean that it should receive and store 4 full

BGP tables and needs 1,2 GB DRAM?

3) what if this is the scenario:

IPS1---eBGP--R1---iBGP--R_CENTRAL----iBGP----R2---eBGP ---ISP2

R_CENTRAL has 2 IBGP peer sessions with R1 and R2 which have eBGP sessions with ISP1 and 2 respectively.

Also R_CENTRAL is route reflector for R1 and R2. R1 and R2 receives full BGP table  from ISP1 and 2.

Will R_CENTRAL receive 2 full BGP tables or just 1 BGP table (since R1 and R2 will send only send its best routes after a while)?

Is it correct that R_CENTRAL will need only 300MB DRAM?

4) aproximately if one router receives full routing table from BGP peer which is cca 300.000 routes then it needs aproximately 300MB DRAM.

This include BGP as well as RIB table. Is this statement correct?



3 Replies 3

ajay chauhan
Rising star
Rising star

The amount of memory required to store BGP routes depends on many factors, such as the router, the number of alternate paths available, route dampening, community, the number of maximum paths configured, BGP attributes, and VPN configurations. Without knowledge of these parameters it is difficult to calculate the amount of memory required to store a certain number of BGP routes. Cisco typically recommends a minimum of 512 MB of RAM in the router to store a complete global BGP routing table from one BGP peer. However, it is important to understand ways to reduce memory consumption and achieve optimal routing without the need to receive the complete Internet routing table. Refer to