Cisco 2600: How many IPv4 prefixes can fit in BGP table

Today I wanted to try and see how many IPv4 prefixes can a Cisco 2600 accommodate in BGP table both global and in VRF table. I have lying around a Cisco 2621XM with 64MB of RAM, so I said to stress it a bit like in the old days when it was productive.

I did use the bgp_simple tool to test with the latest full Internet prefixes table (dated 2013.03.09). For those of you not familiar with bgp_simple, it’s a script capable of BGP peering and route injection. I would recommend to check the script webpage as it’s an awesome tool.

First, I did use the Global table to store all BGP prefixes. The router issued a %SYS-2-MALLOCFAIL error after receiving 44791 prefixes and few seconds later it dropped the BGP neighborship peering.

BB1#sh ip bgp sum | b Nei
Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.182.1   4 65000 1194845      95  1181910  360    0 00:10:57    44791
 
BB1#
*Feb 10 21:22:49.383: %SYS-2-MALLOCFAIL: Memory allocation of 65536 bytes failed from 0x8006A11C, alignment 0 
Pool: Processor  Free: 64176  Cause: Not enough free memory 
Alternate Pool: None  Free: 0  Cause: No Alternate pool 
 -Process= "BGP Router", ipl= 0, pid= 32 -Traceback= 0x8119EA40 0x80057D14 0x80059F18 0x8005A75C 0x8006A120 0x8006AE9C 0x8192D52C 0x80DFDD34 0x80DFE708 0x80DFF60C 0x82BA5A60 0x80DFF6E4 0x80DD8694 0x802435AC 0x80246CB0
*Feb 10 21:23:00.395: %BGP-5-ADJCHANGE: neighbor 192.168.182.1 Down No memory
*Feb 10 21:23:00.515: %BGP-3-NOTIFICATION: sent to neighbor 192.168.182.1 3/1 (update malformed) 0 bytes 
BB1# FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF 0037 0200 0000 1C40 0101 0040 020E 0206 FDE8 9465 12EC 1D31 00D1 5821 4003 04C0 A8B6 0117 433F E0

For second test I did create VRF A and the BGP neighborship was established over an interface in that VRF, so all prefixes injected by bgp_simple arrived in the VRF table. This time it took only 33321 prefixes for the router to spit an error and drop the BGP connection.

BB1#sh ip bgp vpnv4 vrf A sum | b Nei
Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.182.1   4 65000  439682      31   323732  534    0 00:09:24    33321
 
*Feb 10 21:37:22.323: %SYS-2-MALLOCFAIL: Memory allocation of 2920 bytes failed from 0x8006A11C, alignment 0 
Pool: Processor  Free: 8584  Cause: Memory fragmentation 
Alternate Pool: None  Free: 0  Cause: No Alternate pool 
 -Process= "BGP Router", ipl= 0, pid= 32 -Traceback= 0x8119EA40 0x80057D14 0x80059F18 0x8005A75C 0x8006A120 0x8006AE9C 0x80DEB7B0 0x80DCC800 0x80E3DCC8 0x80E3B62C 0x80E2A244 0x80E2AE30 0x80DD0B14 0x80DD7F08 0x802435AC
*Feb 10 21:37:31.011: %BGP-5-ADJCHANGE: neighbor 192.168.182.1 vpn vrf A Down No memory
*Feb 10 21:37:31.251: %BGP-3-NOTIFICATION: sent to neighbor 192.168.182.1 3/1 (update malformed) 0 bytes 
BB1#sh ip bgp vpnv4 vrf A sum | b Nei FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF 0052 0200 0000 3740 0101 0040 020A 0204 FDE8 2236 1AAE 18B7 4003 04C0 A8B6 01C0 081C 18B7 03E9 18B7 A028 1AAE 3E80 1AAE 3F6A 1AAE 59D9 1AAE 89EA 2236 1AAE 1440 3B90

For those of you curious about why it took less prefixes to exhaust memory in VRF vs non-VRF, the reason is that in VRF you have more memory consumption per IPv4 prefix. Ivan Pepelnjak explained it very well in his blog post about running Internet in VRF.

I’ll check what other old Cisco routers I have around to see their BGP table limit.


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