[c-nsp] GSR: 3GE-GBIC-SC v4 traffic influenced by v6 traffic?

Sascha Pollok nsp-list at pollok.net
Fri Feb 26 05:54:41 EST 2010

Good day,

the 3GE-GBIC-SC card does IPv6 in software on the linecard. Is anyone
aware of a problem that IPv6 traffic that is software-forwarded
could influence IPv4 hardware forwarding? It looks like a linecard
could hit 100% with ~80 Mbit/s of v6 traffic + other tasks
like TAG Stats Backgr or CEF process etc and also suddenly stops
forwarding IPv4 traffic or AT LEAST stops responding to ICMP Echo
(directed to the interface IP) or loses IP protocols like
LDP or OSPF which could point to problems GRP/PRP -> Interface.
It seems like this happens exactly at that moment when the
card's CPU hits 100%.

I had expected that the CPU forwarded v6 could lead to higher
RTT for v6 etc but I am surprised that it seems like it could
influence IP protocols.

I know that the Engine 2 card is not state-of-the-art especially
for v6 traffic but I am looking for a confirmation that this
behaviour is indeed something that could happen. If so, I might
go to for 4GE-SFP-LC or similar which does v6 in hardware AFAIK.

Thank you

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