Configuring Route Distinguishers for Routing Instances

Each routing instance must have a unique route distinguisher associated with it. The route distinguisher is used to place bounds around a VPN so the same IP address prefixes can be used in different VPNs without having them overlap.

We recommend that you use a unique route distinguisher for each routing instance that you configure. Although you could use the same route distinguisher on all PE routers for the same VPN, if you use a unique route distinguisher, you can determine the CE router from which a route originated.

To configure a route distinguisher, include the route-distinguisher statement:

route-distinguisher (as-number:number | ip-address:number);}

You can include the statement at the following hierarchy levels:

[edit routing-instances routing-instance-name]
[edit logical-systems logical-system-name routing-instances routing-instance-name]

The route distinguisher is a 6-byte value that you can specify in one of the following formats:

as-number:number, where as-number is your assigned AS number and number is any 2-byte or 4-byte value. The AS number can be in the range from 1 through 4,294,967,295. If the AS number is a 2-byte value, the administrative number is a 4-byte value. If the AS number is 4-byte value, the administrative number is a 2-byte value.

A route distinguisher consisting of a 4-byte AS number and a 2-byte administrative number is defined as a type 2 route distinguisher in RFC 4364 BGP/MPLS IP Virtual Private Networks.

Note: In Junos OS Release 9.1 and later, the numeric range for AS numbers is extended to provide BGP support for 4-byte AS numbers, as defined in RFC 4893, BGP support for Four-octet AS Number Space. All releases of the Junos OS support 2-byte AS numbers. To configure a route distinguisher that includes a 4-byte AS number, append the letter “L” to the end of the number. For example, a route distinguisher with the 4-byte AS number 7,765,000 and an administrative number of 1,000 is represented as 77765000L:1000.

In Junos OS Release 9.2 and later, you can also configure a 4-byte AS number using the AS-dot notation format of two integer values joined by a period: <16-bit high-order value in decimal>.<16-bit low-order value in decimal>. For example, the 4-byte AS number of 65,546 in plain-number format is represented as 1.10 in the AS-dot notation format.

ip-address:number, where ip-address is an IP address in your assigned prefix range (a 4-byte value) and number is any 2-byte value. The IP address can be in the range from 0 through 4,294,967,295 (2³² – 1).

If the router you are configuring is a BGP peer of a router that does not support 4-byte AS numbers, you need to configure a local AS number. For more information, see Establishing a Peer Relationship Between a 4-Byte Capable Router and a 2-Byte Capable Router Using a 4-Byte AS Number in the Using 4-Byte Autonomous System Numbers in BGP Networks Technology Overview .

Configuring Route Distinguishers for Routing Instances

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