Four byte AS number support in Cisco IOS

Last week IOS release 12.4(24)T appeared on CCO. One of the significant improvements in that release (I can’t manage to get enthusiastic about new kludges to support the SIP morass) is the support for 4-byte BGP AS numbers.

Finally an enterprise network that uses Cisco routers to connect to the Internet can use the new AS numbers distributed by the regional registries (assuming you’re brave enough to run 12.4(24)T on your production gear). The Service Providers using 7600 routers will have to wait … corresponding 12.2SR release is not yet available.

Hat tip to Tassos @ CCIE in 3 months: he was the first to write about this feature.


  1. Hi everyone,

    Can I run 4 byte as number on catalyst 3750, I checked cisco site and there was not available ioses
  2. So, you've got the answer ;)

    Seriously, if you need to run public BGP, it might be better to use a router.
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