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extend VLANs between two DCs with L3 DCI

ThorpedoUK
Level 1
Level 1

Hi all

 

So I am running a simulation in VIRL where I have the following

 

DC 1

 

2 x Cisco N9Ks

 

DC2

 

2 x Cisco N9Ks

 

and a layer 3 DCI between them (routed port on each opposing N9K running OSPF) - in this scenario (ie not trunked DCI) is it possible to extend VLANs between each DC using HSRP? (bearing in mind i am using the n9k here) the issue is obviously OSPF is going to be advertising the same subnet in both locations so any traffic traversing the DCI on an extended VLAN may not come back.....

 

An example is where say there are two ASA with two different DMZs and I route from extended vlan at dc2 to dc1 asa dmz, on the reply it is not going to traverse back across the DCI as it will see a local subnet advertised.

 

please excuse me i am trying to learn here and its tough in your own lab, but i am trying to learn the hard ways as well as the easy ways. is it even possible in this scenario?

 

thanks

1 Reply 1

Rick1776
Level 5
Level 5
The only way to successfully to do this is with VxLAN EVPN (anycast gateways) and or use OTV To extend the layer 2 network. the only issue is that the Nexus 9K's don't support OTV only VxLAN EVPN. You could add a single N7K to each DC side and make those the OTV's AED.

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus7000/sw/otv/config/cisco_nexus7000_otv_qsg_config_guide_8x.html







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