Discussion

In the community identifier, you can use regular expressions to specify matches for
the AS number and member identifier. The regular expressions have the same format
as those for AS paths, consisting of a term and an operator, and they use the
same operators as AS paths (see Table 13-1).
Because the routing policy in the recipe matches an AS number, we need the set aspath
command to define which ASs to look for.
The second part of the process is creating a routing policy that references the community.
The routing policy checks for BGP routes that have 65505 in their AS path and
adds the community customer to any that match. Here’s what the policy-options portion
of the configuration looks like:
[edit policy-options]
aviva@RouterF# show
policy-statement community-add {
term match-route {
from {
protocol bgp;
as-path AS65505-path;
}
then {
community add customer;
accept;
}
}
}
community customer members 65500:1234;
as-path AS65505-path "65505 .*";
As with all policies, to have it take affect, apply it to BGP. Here, we apply it with an
import statement on routes being learned from the EBGP peer to AS 65505.
The detail option of the show route command lists the community attributes associated
with a route:
aviva@RouterF> show route detail 192.168.18.1
inet.0: 18 destinations, 22 routes (18 active, 0 holddown, 0 hidden)
192.168.18.1/32 (1 entry, 1 announced)
*BGP Preference: 170/-101
Next-hop reference count: 18
Source: 10.0.31.1
Next hop: 10.0.31.1 via t1-0/0/3.0, selected
State:
Local AS: 65500 Peer AS: 65505
Age: 2d 18:35:30 Metric: 65
Task: BGP_65505.10.0.31.1+2079
Announcement bits (3): 0-KRT 3-BGP.0.0.0.0+179 4-Resolve tree 1
AS path: 65505 I
Communities: 65500:1234
Localpref: 100
Router ID: 192.168.14.1
466 | Chapter 13: BGP
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