Multicast over GRE causes 100% CPU on C2960XR-48TD

[msantiveri]

Hello,

I've created a GRE tunnel between two Catalyst 2960XR-48TD switches running 15.0(2)EX5 to pass multicast traffic through it.

Sporadic multicast traffic pass normally but when bulk traffic happens (6Mbps a day during 15 minutes) the CPU goes at 100%. The multicast routing table consists of only 3 hosts.

Has somebody faced this situation? IOS issue or this switch is just not able to handle this type of traffic?

Thanks,

Miquel

[Martin Hruby]

Hello Miquel

GRE tunneling is not supported in hardware on most Catalyst platforms and therefore all traffic going across your tunnel interface has to be software switched. With increasing amount of traffic, the CPU utilization grows. I would not recommend having a GRE tunnel between two 2960xr switches for purposes other than switch management.

Best regards,
Martin

[msantiveri]

OK. It's clear then that I have to move that tunnel to a router.

Thanks a lot,

Miquel