Information Technology Reference
In-Depth Information
BGP Edge Router Configuration Template (Continued)
Example 9-3
neighbor CUST_PRIV_ASN remote-as 65000
neighbor CUST_PRIV_ASN remove-private-as
!
neighbor CUST_PARTIAL peer-group
neighbor CUST_PARTIAL description Customers Receiving Partial Routes
neighbor CUST_PARTIAL version 4
neighbor CUST_PARTIAL password <Customer Password>
neighbor CUST_PARTIAL route-map PARTIAL_ROUTES out
neighbor CUST_PARTIAL remove-private-as
neighbor CUST_PARTIAL default-information originate
!
neighbor CUST_FULL peer-group
neighbor CUST_FULL description Customers Receiving Full Routes
neighbor CUST_FULL version 4
neighbor CUST_FULL remove-private-as
neighbor CUST_FULL password <Customer Password>
...
!
route-map PARTIAL_ROUTES permit 10
match community 1
!
route-map PARTIAL_ROUTES deny 20
!
ip community-list 1 permit <Customer Routes Community>
ip community-list 1 deny
!
The edge architecture template provides the basic BGP configuration for the edge. It does
not include prefix filtering and BGP community application. These can be applied to the
basic template. These topics are covered later in this chapter.
General BGP Settings
In the configuration templates provided in the previous sections, a couple settings are
applied on all routers: autosummarization and BGP synchronization. This section briefly
covers those commands.
BGP's autosummarization feature dates back to the days of classful routing. This feature
should always be disabled in an ISP environment. If autosummarization is enabled, the
router summarizes prefixes along their classful boundary when the prefixes are generated—
typically at the point of redistribution. This means that if an ISP has a /19 allocation in
traditional Class B space, autosummarization advertises the entire /16, even though the ISP
has been assigned only one-eighth of that /16. This can result in the ISP's attracting traffic
for which it is not the destination.
The BGP synchronization feature is intended for networks that are not running BGP on all
contiguous routers in the forwarding path. The typical ISP runs BGP on all routers, so it
