[j-nsp] BGP extended community attribute

[Pedro Roque Marques]

jjsyed  writes:

> Hi, There are two format to define extended community value, AS:VAL
> and ip-address-VAL
 
> Which one is better then other entirely depend upon the design and
> specific requirements. I am wondering if any of you have any
> thoughts which one is widely used in the industry and also shed some
> lights on pros and cons for each other.
 
Kind of depends a lot of what you are trying to identify: a network
wide property or system specific.

For instance, if you are talking about a Route Target extended
community (used to identify a VPN), most xSPs use the AS:VAL format
where VAL is some sort of numeric customer id.

Route Targets are meaninful network wide.

If one the other hand you are assigning Route Distinguishers (which
are not extended communities but also have the same format choice)
then, if the assignment policy is one RD per PE, the format
<lo0-address>:<num> is more common (you can get that done for you via
[routing-options route-distinguisher-id]).

  Pedro.