The base TRILL (Transparent Interconnection of Lots of Links) protocol provides optimal pair-wise data frame forwarding for Layer 2 intra-subnet traffic but not for Layer 3 inter-subnet traffic. A centralized gateway solution is typically used for Layer 3 intersubnet traffic forwarding but has the following issues:

1. Sub-optimum forwarding paths for inter-subnet traffic.

2. A centralized gateway that may need to support a very large number of gateway interfaces in a Data Center, one per tenant per Data Label used by that tenant, to provide interconnect functionality for all the Layer 2 Virtual Networks in a TRILL campus.

3. A traffic bottleneck at the gateway.

This document specifies an optional TRILL distributed gateway solution that resolves these centralized gateway issues.