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Due to a new set of routes published yesterday, the internet has effectively undergone a schism. All routers with a TCAM allocation of 512k (or less), in particular Cisco Catalyst 6500 and 7600's, have started randomly forgetting portions of the internet.
"Cisco also warned its customers in May that this BGP problem was coming and that, in particular, a number of routers and networking products would be affected. There are workarounds, and, of course the equipment could have been replaced. But, in all too many cases this was not done.. Unfortunately, we can expect more hiccups on the Internet as ISPs continue to deal with the BGP problem." says Steven J. Vaughan-Nichols of ZDNet.
Is it time to switch to all IPv6 yet?
Earlier today there was a hiccup in the Internet as many routers started "flapping". BGPmon.net tracks the BGP activities on the global Internet, and came up with the following analysis:
Folks quickly started to speculate that this might be related to a known default limitation in older Cisco routers. These routers have a default limit of 512K routing entries in their TCAM memory. [...] Right now the number of prefixes is still several thousands under the 512,000 limit so it shouldn't be an issue. However when we take a closer look at our BGP telemetry we see that starting at 07:48 UTC about 15,000 new prefixes were introduced into the global routing table.
Whatever happened internally at Verizon caused aggregation for their prefixes to fail which resulted in the introduction of thousands of new /24 routes into the global routing table. This caused the routing table to temporarily reach 515,000 prefixes and that caused issues for older Cisco routers.
Luckily Verizon quickly solved the de-aggregation problem, so we're good for now. However the Internet routing table will continue to grow organically and we will reach the 512,000 limit soon again. The good news is that there's a solution for those operating these older cisco routers. The 512,000 route limitation can be increased to a higher number, for details see this Cisco doc.
(Score: 1) by knorthern knight on Thursday August 14 2014, @01:15AM
Over time, smaller ISPs grew, and needed, and acquired more IP addresses. They were usually scattered all over the address space. Has someone considered an effort to swap IP address space to aggregate smaller routes?