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Minimal Configuration
Again, network-number represents the network that is to be advertised
using the BGP process. The IP network specified in the BGP network state-
ment does not have to be directly connected to the router. Network state-
ments within the BGP protocol session allow BGP to advertise routes learned
by an IGP that are contained in the route table. The network mask is applied
because BGPv4 can support subnetting and supernetting. When a logical
BGP mesh is in place, each IGP session should have network statements con-
figured for only those routes learned from the IGP. Network statements
should not be duplicated among internal BGP routers.
BGP configuration can be very complicated. Several different options may be
configured to optimize BGP routing. When only one link is used to peer with
another AS or ISP, the configuration can be straightforward. As more links are
used, or multiple ISPs or autonomous systems are connected to a router, the
configuration becomes increasingly complex.
Verifying BGP Configurations
After BGP is configured, several commands will allow us to verify the BGP
configuration and troubleshoot the operation of BGP. We can also use these
commands to monitor the BGP process and its operations.
Table 8.2 summarizes all of the commands that can be used to verify BGP.
T A B L E 8 . 2
BGP Monitoring Command Summary
show ip bgp
Shows all BGP configuration information for
the selected interface.
show ip bgp neighbors
Shows all configured BGP neighbors. It pro-
vides detailed statistics and information
about each neighbor.
show ip bgp community
Displays routes belonging to the specified
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