Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring BGP
Configuring Advanced BGP Features
IPC-325
Cisco IOS IP Configuration Guide
Indicating Backdoor Routes
You can indicate which networks are reachable by using a backdoor route that the border router should
use. A backdoor network is treated as a local network, except that it is not advertised. To configure
backdoor routes, use the network backdoor command, beginning in router configuration mode:
Modifying Parameters While Updating the IP Routing Table
By default, when a BGP route is put into the IP routing table, the MED is converted to an IP route metric,
the BGP next hop is used as the next hop for the IP route, and the tag is not set. However, you can use a
route map to perform mapping. To modify metric and tag information when the IP routing table is
updated with BGP learned routes, use the following command in router configuration mode:
Setting Administrative Distance
Administrative distance is a measure of the preference of different routing protocols. BGP uses three
different administrative distances: external, internal, and local. Routes learned through external BGP are
given the external distance, routes learned with iBGP are given the internal distance, and routes that are
part of this autonomous system are given the local distance. To assign a BGP administrative distance,
use the following command in router configuration mode:
Changing the administrative distance of BGP routes is considered dangerous and generally is not
recommended. The external distance should be lower than any other dynamic routing protocol, and the
internal and local distances should be higher than any other dynamic routing protocol.
Adjusting BGP Timers
BGP uses certain timers to control periodic activities such as the sending of keepalive messages and the
interval after not receiving a keepalive message after which the Cisco IOS software declares a peer dead.
By default, the keepalive timer is 60 seconds, and the hold-time timer is 180 seconds.You can adjust
these timers. When a connection is started, BGP will negotiate the hold time with the neighbor. The
smaller of the two hold times will be chosen. The keepalive timer is then set based on the negotiated hold
time and the configured keepalive time.
Command Purpose
Router(config-router)# network ip-address backdoor
Indicates reachable networks through backdoor routes.
Command Purpose
Router(config-router)# table-map map-name
Applies a route map to routes when updating the IP routing
table.
Command Purpose
Router(config-router)# distance bgp
external-distance internal-distance local-distance
Assigns a BGP administrative distance.