discussion: Enabling IPv6 on Cisco 6500/7600 breaks IPv4 Internet connectivity

Mikael Abrahamsson swmike at swm.pp.se
Tue Jun 26 07:36:20 CEST 2012

On Mon, 25 Jun 2012, Ranganath Hande wrote:

> It is fairly common for RP utilization to go up initially when either v4 
> or v6 internet BGP peer comes up first time--due to large number of BGP 
> prefixes that router has to process. In case of v6, impact is more 
> visible as resource utilization is 4 times higher. Possible solutions 
> are --

In case of PFC3B(-XL), this is also of interest once IPv6 traffic is 


PFC3B will by default punt IPv6 packets with fragmentation header to RP
and route them there, with the obvious performance penalty this incurs.

Workaround is to change this behaviour, meaning ACLs won't work for
packets with fragmentation header anymore:

    #platform ipv6 acl fragment hardware ?
      drop     Drop IPv6 fragments at hardware
      forward  Forward IPv6 fragments at hardware

PFC3C is supposed to not be affected.

Mikael Abrahamsson    email: swmike at swm.pp.se

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