Cisco IOS Software Release 110 Extended access lists are permitted in Release 120 Configuration Example Conditional Default Route Advertisement

Figure 8-6 shows an autonomous system that has a connection to the Internet through Router B. The network directly connected to the Internet,, is to be used as the default route for the autonomous system. A static default route could be used on every router in the AS, but this is not the preferred method. These static routes require a high degree of maintenance. If the default route on Router B changes, every static route on every router in the AS needs to be changed. The preferred method is to dynamically propagate the default route attached to Router B throughout the AS. The following configuration contains the necessary instructions to enable Router B to propagate the default route only if the default route exists.

Figure 8-6. Conditionally Advertising a Default Route

Figure 8-6. Conditionally Advertising a Default Route peer-group-name— Name of the peer group. See section 8-19.

text— Line describing the neighbor (1 to 80 characters).

Purpose: The description option performs a function that is similar to a comment in a software program. This function simply helps the reader determine the purpose of the code or, in the BGP case, the identification of the neighbor. Adding a neighbor description to a BGP configuration does not affect the operation of BGP. The description should convey useful information that can be quickly used to identify neighbors. For simple scenarios that have few neighbors, the description option has limited usefulness. For an ISP that has multiple neighbor relationships, however, you can use the description command to identify a neighbor without having to memorize its IP address.

Cisco IOS Software Release: 11.3

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