Tier0-Tier1 gateway connectivity in NSX-T(IPv6)

For a multi-tier IPv6 routing topology, each Tier-0-to-Tier-1 peer connection is provided a /64 unique local IPv6 address from a pool i.e. fc5f:2b61:bd01::/48. A user has the flexibility to change this subnet range and use another subnet if desired. Similar to IPv4, this IPv6 address is auto plumbed by system in background.

IPv6 routing between Tier-0 and Tier-1 Gateway is auto plumbed similar to IPv4 routing. As soon as Tier-1 Gateway is connected to Tier-0 Gateway, the management plane configures a default route (::/0) on Tier-1 Gateway with next hop IPv6 address as Router link IP of Tier-0 Gateway (fc05:2b61:bd01:5000::1/64, as shown below). To provide reachability to subnets connected to the Tier-1 Gateway, the Management Plane (MP) configures routes on the Tier-0 Gateway for all the LIFs connected to Tier-1 Gateway with a next hop IPv6 address as Tier-1 Gateway Router link IP (fc05:2b61:bd01:5000::2/64, as shown below). 2001::/64 & 2002:/64 are seen as “Tier-1 Connected” routes on Tier-0.

Now the next question is, where we can change this default values?

While creating T0 gateway click on Additional settings.

In the T0-T1 Transit Subnets field, enter one or more subnets.

These subnets are used for communication between this gateway and all tier-1 gateways that are linked to it. After you create this gateway and link a tier-1 gateway to it, you will see the actual IP address assigned to the link on the tier-0 gateway side and on the tier-1 gateway side. The address is displayed in Additional Settings > Router Links on the tier-0 gateway page and the tier-1 gateway page. The default is 100.64.0.0/16.