Cisco 7600 PFC3B(XL) and IPv6 packets with fragmentation header

Christopher Morrow morrowc.lists at
Fri Sep 30 16:44:29 UTC 2011

On Fri, Sep 30, 2011 at 12:38 PM, Nick Hilliard <nick at> wrote:
> On 30/09/2011 17:30, Christopher Morrow wrote:
>> traceroute is really an example of 'packet expired, send
>> unreachable'... that, today is basically:
>>   o grab 64bytes of header (or something similar)
>>   o shove that in a payload
>>   o use the src as the dst
>>   o stick my src on
>>   o set icmp
>>   o crc and fire
>> there's not really any need to do this in the slow path, is there?
> there are unconfirmed rumours that icmp ping and traceroute are handled by
> hardware on the asr1k.  I don't know if they are true.   But you're right -

some platforms do some/all of this in hardware, yes. (I forget the matrix)

> it would be good to support this without resorting to hammering the routing
> engine.  I don't really like the idea of punters running traceroutes
> reducing my bgp convergence time.

this is exactly why punting anything NOT management and/or
routing-protocols should be banned. Thanks for making that point


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