Information Technology Reference
In-Depth Information
Table 9-3
Customer Advertisement Suppression Communities
Suppression Target
BGP Community
Transit
<ISP ASN>:210
Peering
<ISP ASN>:220
Customer
<ISP ASN>:230
The second level of granularity allows the customer to request AS prepending or complete
suppression of advertisement on a per-AS basis. This is commonly not done for every
ASN—only for major peers. The community scheme for this is shown in Table 9-4.
Table 9-4
AS Prepending and Advertisement Suppression Communities
BGP Community
How the ISP Policy Is Applied
65000:<upstream ASN>
Suppresses advertisement to <upstream ASN> peers.
65100:<upstream ASN>
Prepends <ISP ASN> one time to <upstream ASN> peers.
65200:<upstream ASN>
Prepends <ISP ASN> two times to <upstream ASN> peers.
65300:<upstream ASN>
Prepends <ISP ASN> three times to <upstream ASN> peers.
65400:<upstream ASN>
Prepends <ISP ASN> four times to <upstream ASN> peers.
65500:<upstream ASN>
Prepends <ISP ASN> five times to <upstream ASN> peers.
The private ASN determines the action, and the upstream ASN is the upstream peer on
which the action should be taken. This method, which is easy to use and remember, is used
by at least one provider. The new route maps for controlling upstream prefix advertisement
are shown in Example 9-7.
Route Maps for Controlling Upstream Prefix Advertisement
Example 9-7
route-map peer_outbound_AS1000 deny 10
match community 20
!
route-map peer_outbound_AS1000 permit 20
match community 21
set as-path prepend 100
!
route-map peer_outbound_AS1000 permit 30
match community 22
set as-path prepend 100 100
!
route-map peer_outbound_AS1000 permit 40
match community 23
set as-path prepend 100 100 100
