Enabling IPv6 on Cisco 6500 breaks IPv4 Internet connectivity.

Jared Mauch jared at puck.nether.net
Sun Jun 24 00:14:11 CEST 2012

Is this sup2t or 720?

Jared Mauch

On Jun 23, 2012, at 5:50 PM, Jim Trotz <jtrotz at gmail.com> wrote:

> Final update:
>    After much testing in the lab and working with Cisco TAC (almost no help),
>    I have reached a conclusion about the problem - its a hardware limitation.
>    Enabling IPV6 routing on a 6500 (with XL cards) and a full Internet routing
>    table in a VRF exceeds the limits of SP processing, The SP goes to 99%
>    utilization reconfiguring something but eventually recovers. In the lab
>    this took almost 5 minutes!  In real life with many 10Gb interfaces active
>    - who knows!!
>    The problem is that the router still passes enough traffic that EIGRP and BGP stay
>    up, but all user traffic is "black hole'd" due to the 1-10kbs effective throughput.
>    It looks like this may be a one time event, but neither Cisco TAC or the BU
>    could say for sure this wouldn't happen again under some kind of BGP flap
>    of VRF reconfig.
>    Our TCAM limit is 512K ipV4 routes now and we have 409K routes today.
>    We will probably resort to filtering down the BGP learned routes to 100-200K  and 
>    then  default for everything else to our Internet routers and then go shopping
>    for a new router.
>    The problem isn't noticeable until we have more than about 250K routes.
>    There was no interest in redesigning the network to not use VRFs for the
>    Internet table. 
>   Once IPV6 is enabled and all is stable we will probably go shopping for new routers.
>    Thanks again for everyone's suggestions, it helped us figure out the root
>    cause.

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