Information Technology Reference
In-Depth Information
Example 5-35
BGP Configuration for R12
router bgp 65105
no auto-summary
no synchronization
neighbor 10.1.3.10 remote-as 65100
neighbor 10.1.3.10 default-originate
distance bgp 200 220 220
bgp bestpath compare-routerid
!
Example 5-36
BGP Configuration for R13
router bgp 65105
no auto-summary
no synchronization
neighbor 10.1.1.4 remote-as 65100
neighbor 10.1.1.4 default-originate
distance bgp 200 220 220
bgp bestpath compare-routerid
!
After the BGP configurations are in place, the BGP infrastructure must be validated to
ensure that routing information will be available to provide full reachability when the
EIGRP adjacencies over the Ethernet DMZ in each location are torn down. This stage
creates additional memory requirements on the BGP speaking routers, because they will
carry multiple copies of each prefix. The prefixes will exist in BGP and in EIGRP on these
routers. Also, the prefixes will be injected into BGP in multiple places. If the BGP learned
prefixes were being injected into the routing table, this could cause severe routing
problems, but the higher administrative distance for BGP will prevent this.
In the sample configurations, the MED is set to Internal for all prefix advertisements via
eBGP from the border routers to the core routers. This results in the core routers selecting
the optimal path for each prefix in the BGP decision process, as follows:
Step 1
Validate that all BGP sessions reach the Established state using the
show
ip bgp summary
command.
Step 2
Verify that prefix advertisement is consistent. Choose prefixes from each
location, and verify in the core routers that the prefix is in the BGP table
and is correctly chosen by the BGP decision process. This is done with
the
show ip bgp
command. Confirm that the correct next hop is set for
these prefixes in the BGP table.
The next hop for every iBGP learned prefix in the four core routers
should be a loopback address in the 172.16.0.0/16 network. The next hop
for every eBGP learned prefix in the core routers should be the IP address
