Route Target Regular Expressions. The route targets that you place in a routetarget export. Extended communities such as target and origin may consist of two regular expressions separated by the ampersand character.
In this article Ill give a very quick overview of how they work and then will give you a few useful examples to show why they are so useful. Regular Expressions are used often for BGP route manipulation or filtering. Many network engineers dont know Regular Expressions.
The first expression is applied to the as-value of the community string and the second to the local administrative value.
2_ All routes from a directly connected neighbor in AS 2. In this lesson well take a look at some useful regular expressions. Type target originas-numcomm-value The keywords target or origin denote the community as an extended community of type route target or route origin respectively. If the use-regex OR rewrite-target annotation is used on any Ingress for a given host then the case insensitive regular expression location modifier will be enforced on ALL paths for a given host regardless of what Ingress they are defined on.
