Routing via External Router with EPG outs (need contract)
Quick question - scenario:
I have two EPGs in my ACI fabric, call them EPG1 and EPG2.
Those two EPGs connect to VLANs 10 and 20 respectively in a legacy N7/5/2k fabric via EPG-based L2 outs (so, EPG1 links to VLAN 10 in the legacy fabric, and EPG2 links to VLAN 20 in the legacy fabric).
All routing is via SVIs on the N7Ks in the legacy fabric.
Now, my belief (right or wrong!) is that if I want to get from a host in EPG1 to a host in EPG2, the packets will go from the host in EPG1 out of the ACI fabric via the EPG1 out onto VLAN 10, hit the VLAN 10 SVI on the N7k, then route across to the VLAN 20 SVI on on N7K, then out onto VLAN 20, then via the EPG2 out back into the ACI fabric arrive at the EPG2 host.
Now the question is - is a contract needed in this case because the traffic is going from a host in EPG1 to a host in EPG2?
My understanding is that a contract is not required because we are using EPG-based outs, and the routing is on an external router. Am I correct?
The are basically two ways to extend the L2 domains in ACI: a static path connection within an EPG and a Bridged Outside Network connection which also configures an external EPG. For devices to communicated from one EPG to another the will need a contract to allow this.
I hope this helps.
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