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Router connection in a vPc Topology

Hello All,

I have to connect a router (C3560E) to a vPC topology (2 * Nexus5596)

I would like to create a vPC on Nexus 5500 side and a Port-channel on router side.

Regarding L3 aspects all should be included in the same interconnection VLAN with vlans interfaces.

From my knowledge with Nexus 7000 this configuration is not supported because if packets use the vPC peer link the packets would be dropped.

But with Nexus 5596 this configuration seems to be supported (expect for multicast traffic) :

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/operations/n5k_L3_w_vpc_5500platform.html#wp998473

Sending traffic over the peer-link to the correct gateway is acceptable for data forwarding, but it is suboptimal because it makes traffic cross the peer link when the traffic could be routed directly.

The packets passing throught the peer link won't be droped. This configuration can also be improved with the feature "peer-gateway" to avoid to forward the packets to the vPC peer link.

Does someone ever tested this configuration ?.

Do you know why N7000 are not supporting also this configuration ?.

Thank you for your feedback.

David.

Everyone's tags (5)
2 REPLIES
Bronze

Re: Router connection in a vPc Topology

Although configuration guide says "Layer 3 peering" but I still doubt that routing protocol neighbor relation ship is supported between 3560E router and two nexus 5596. You can still do static route on 3560E router using next hop as FHRP virtual IP along with peer-gateway command on each Nexus 5596.

Cisco Employee

Re: Router connection in a vPc Topology

Hi David ,

As far i remember the VPC concept is not changed from N7k to N5k.

There are still limitaion on how you configure your L3 connectivity.

Packet coming with ttl=1 will still be dropped even if you use peer-gateway command.

Switch will try to L3-switch the unicast packet (on behalf of other due to peer-gateway)

As packet has TTL==1 it will be dropped .

Regards

Vishwa

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