Route distinguishers

The route distinguisher (RD) is an 8-byte value consisting of two major fields, the Type field and Value field. The Type field determines how the Value field should be interpreted. The 7750 SR and 7950 XRS implementation supports the three (3) Type values as defined in the standard.

Figure: Route distinguisher

The three Type values are:

• Type 0: Value Field — Administrator subfield (2 bytes)

  • Assigned number subfield (4 bytes)

  • The administrator field must contain an AS number (using private AS numbers is discouraged). The Assigned field contains a number assigned by the service provider.

• Type 1: Value Field — Administrator subfield (4 bytes)

  • Assigned number subfield (2 bytes)

  • The administrator field must contain an IP address (using private IP address space is discouraged). The Assigned field contains a number assigned by the service provider.

• Type 2: Value Field — Administrator subfield (4 bytes)

  • Assigned number subfield (2 bytes)

  • The administrator field must contain a 4-byte AS number (using private AS numbers is discouraged). The Assigned field contains a number assigned by the service provider.