Introduction

Route Distinguishes is a a value use in the vpnv4/6 address-family to make each VPN prefix distinguishable, allowing for overlap between VPNs.

Route Distinguishes

• VPN-IPv4 address is made up for 12 bytes, where 8 bytes are RD and 4 bytes is the IPv4 address.
• RD consists of three field (total length 64 bits):
  • • Type (2 bytes)- see encoding of RD below.
    • Administrator (2 or 4 bytes) - either ASN or IPv4 address (see encoding for examples).
    • Assigned number field (2 or 4 bytes) - could be IPv4 address or a another values (see encoding for examples).
• VPNv4 routes with the same RD will use the BGP best path selection algorithm (see encoding for examples).

Encoding of RD

• Type 0 - ASN (administrator 2 bytes), Value (Assigned number field 4 bytes)
  • Exp: 12440:99388434
• Type 1 - IPv4 (administrator 4 bytes), Value (assigned number field 2 bytes)
  • Exp: 14.1.2.3:5533
• Type 2 - ASN (administrator 2 bytes), IPv4 (Assigned number field 4 bytes)
  • Exp: 12440:14.1.2.3

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