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routing engine in a mixed chassis N7K



I would like to know how the routing in an N7K mixed chassis works, if I have more than one M-series module.

Which module processed the routing? Which of the m modules? Can I configure this? (hardware proxy layer-3 routing?)

What should I do that this do not happen?


Why should the N7K transport the paket this way?

Thanks and regards.

2 Replies 2

Chad Peterson
Cisco Employee
Cisco Employee


Only the 2nd picture you put here shows up, so I can only comment on that. 

So by default when when you are doing proxy L3 routing the F1 modules will load balance across all M1 modules to perform the route lookups.  However you can configure this and choose which modules should be doing the routing:

The main reason why the situation in the 2nd picture happens is that the F1 module doesn't know which port we will need to send the traffic out after it gets routed, so it sends it to any M1 module for the lookup.  Once that M1 module performs the lookup it will send it to the correct destinaion port, so it may have two passes through the fabric.


Hi Chad,

And if the packet should Egress trough the same F1 card. would this be a problem ?

Imagine that you have to machines in Vlan A and B in an access switch that has an uplink to the F1 card in 7K, the 7K would need to do the inter-velan routing, since the uplink is made in an F1 card, i have the following questions:

1. I will have to configure "hardware proxy layer-3 forwarding" to get L3 features from another M1 card:

1.1. What are the rules for this config ?

1.2. Could this uplink be configured to more than one M1 card (for redundancy purpose) ?

1.3. Will this solution work since the Packet ingress and egress trough the same port (from the 7k point of view) ?

Kind Regards,

Bruno Fernandes

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