Hi All,


The senario I have is running otv over CSR1000V in vcloud director environment. Basically I depolyed two csr1000v ova in the same Org VDC, then connected them (both interface gigabitethernet 2) in the same network (vxlan). Pinging is fine as they are on the same network with ip address in the same subnet.

However, when I used this int g2 as join-interface to setup otv, the AED capable is "No, overlay DIS not elected".

Something I would like to point out :

 1. I am using unicast-only in this senario, one of those 2 CSR1000v is adj-server.

 2. mtu size is jumbo, so don't worry about the mtu 1542 df-bit prerequisite.

 3. I have another similar lab in only one esxi host, which means there is no vxlan at all. Exactly the same configs work perfectly.


BTW, I have setup a capature on the csr1000v, and monitor it for a while. However, there is no UDP 8472 packet (ISIS Hello) bidirectionally at all.


So it's quite confusing me, as the csr1000v should have no idea about the vxlan underlying, then why vxlan would affect the isis hello packet generating and receiving?


Thanks a lot!




  • Hrmm what's the MTU on your VTEP interface?

    Make sure the VTEP MTU is set to something pretty high (might as well go 9000 and make sure all your ESXi hosts are configured this way)

    Make sure your vSwitch supports a sufficient MTU (if not using a distributed switch then check all your hosts.)

    Make sure your CSR 1000v's MTU is set appropriately (this one doesn't need to account for VXLAN encap.)

    Some questions:

    are the esxi host VTEPs on the same subnet or different?

    If you vmotion the two routers to the same host (using otherwise the same config) does it start to work?

    when you debug/do a capture do you see any hellos from one device to the other?



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