Overlap Route in DC DC Failover

[rahmad]

Hi all,

I've question regarding overlap route in AutoVPN.

Recently i read this documentation : https://documentation.meraki.com/MX/Networks_and_Routing/MX_Routing_Behavior#DC-DC_Failover

Let's assume all those DC is Hub with NAT Mode.

1.Based on statement in that documentation, is it true that if DC 2 is down/unreachable by Branch MX, route failover to DC 1 will not happen for 10.1.0.0/16 ?

If so, i seems can't quite understand why that's the case.

I'm assuming once DC 2 is down, route for 10.1.0.0/16 will be deleted in AutoVPN, is this correct ?

2. Is there any other solution so 10.1.0.0/16 can failover to DC 1 ?

Any answer is appreciated, thank you.

[PhilipDAth · Accepted solution]

If you really do have two DCs with the same subnet, then those DCs are probably using layer 2 extension across the sites.  If they have that, then use the two MXs in warm spare mode.  They will then as a single unit, and which ever is up will get the traffic and route it appropriately.

Otherwise if you really want to run active/active, connect each MX to your layer 3 core using a stub network (I quite like /29's these days).  Then use BGP between your core switch and the MX and dynamically advertise routes into the MX and AutoVPN.  Then if a DC does die, the routes stopped getting advertised via BGP, and everything fails over nicely.

[rahmad]

Hi Phillip,

Thank you for your answer!
1 more question, i know if this is a bit more off topic, but can you deploy Passthrough Mode behind router not firewall ?

[ww]

You have a point here.  Why would it not failover.   When the spoke loses connectivity to the hub it also  removes  its  routes..?

[SopheakMang]

Try to troubleshoot first , i also used to meet this case. I want you to check on routing table on each MX make sure no conflict subnet. Then can try to open case , ask merkai support to turn off layer3 summary feature from the back end , then let's see the result.