Tier-0 Tier-1 communication down in an NSX-T 2.4.0 environment
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Tier-0 Tier-1 communication down in an NSX-T 2.4.0 environment


Article ID: 324226


Updated On:


VMware NSX Networking



The following criteria are all met
  •  NSX-T 2.4.0 environment
  •  The T0-T1 transit subnet is non default and is part of the range
  •  T1 connected networks are not visible on the active Edge T0 DR vrf when running "get forwarding"
  •  T0 DR and T1 DR LinkedPort interfaces show no IPv4 address configured, only IPv6 e.g.
Edge1(vrf)> get int
    Interface     : 98147703-a33d-4023-9d34-558832bdc09c
    Ifuid         : 307
    Name          : LinkedPort_T0
    Mode          : lif
    IP/Mask       : fe80::50:56ff:fe56:4455/64;fc66:c650:9440:e800::2/64
    MAC           : 02:50:56:56:44:55
    VNI           : 71683
    LS port       : dcf2124f-a792-4bb1-946f-c05e6d9b5b46
    Urpf-mode     : NONE
    Admin         : up
    Op_state      : up
    MTU           : 1500


VMware NSX-T Data Center 2.x
VMware NSX-T Data Center


NSX-T 2.4.0 introduced support for IPv6.
This code change involved new handling of interfaces with link local addresses.
IPv4 link local subnet is
Any transit subnet interface in the range will be removed and not readded preventing communication between the T0 and T1 routers.
This issue is not present in earlier releases and can impact upgraded or newly installed environments.


This is a known issue affecting NSX-T Datacenter 2.4.0. There is currently no resolution.

The T0-T1 transit subnet must be re-configured to use a different subnet which is not part of
The subnet is sepcified on the T0 router. To make the change the T1 routers must be detached from the T0. Once the change is complete the T1 routers can be readded.