7.5. ESI Label Extended Community

This Extended Community is a new transitive Extended Community having a Type field value of 0x06 and the Sub-Type 0x01. It may be advertised along with Ethernet Auto-discovery routes, and it enables split-horizon procedures for multihomed sites as described in Section 8.3 ("Split Horizon"). The ESI Label field represents an ES by the advertising PE, and it is used in split-horizon filtering by other PEs that are connected to the same multihomed Ethernet segment.

Each ESI Label extended community is encoded as an 8-octet value, as follows:

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    | Type=0x06     | Sub-Type=0x01 | Flags(1 octet)|  Reserved=0   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Reserved=0   |          ESI Label                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The low-order bit of the Flags octet is defined as the "Single-Active" bit. A value of 0 means that the multihomed site is operating in All-Active redundancy mode, and a value of 1 means that the multihomed site is operating in Single-Active redundancy mode.

7.5. ESI Label Extended Community​

7.5. ESI Label Extended Community