Dell Z9000 Configuration Manual page 870

When the routing table across DCs is not symmetrical, there is a possibility of a routing miss by a DC that
do not have the route for the L3 traffic. Since routing protocols will enabled and both the DC's comes in
same subnet there will not be route asymmetry dynamically. But if static route is configured on one DC
and not on the other, it will result is asymmetry. Proxy routing can still be achieved locally by configuring
a static route or default gateway.
Guidelines for Configuring VLT Proxy Gateway
Keep the following points in mind when you configure this functionality:
1. Proxy gateway is supported only for VLT i.e. across VLT domain.
2. The current design will not handle the asymmetric VLAN configuration scenarios such as same VLAN
configured with L2 mode on one VLT domain and L3 mode on the other VLT domain. It is always
required to configure same mode for the VLAN's across the VLT domain.
3. VLAN symmetry within a VLT domain is also to be maintained.
4. The connection between DC's can only be a VLT.
5. Trace route across DC's may possibly show extra hops.
6. Route symmetry has to be maintained across the VLT domains to ensure no traffic drops.
7. If the port-channel specified in the proxy-gateway command is not a VLT LAG then the configuration is
rejected by CLI. The VLT LAG cannot be changed to a legacy LAG when it is part of proxy-gateway.
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VLT Proxy Gateway