Information Technology Reference
In-Depth Information
Here is the high-level summary:
Select R4 as the starting router, and move it out of the forwarding paths.
Step 1
Remove R4's BGP process, and replace it with the confederation config-
uration. Update all other routers with confederation configurations.
Step 2
Create iBGP mesh sessions and intraconfederation eBGP sessions.
Step 3
Update the configurations on R1 and R2 to peer with R4.
Step 4
Move R6 from member AS 100 to member AS 65001, and put R4 back
in the forwarding paths.
Step 5
Move R7 from member AS 100 to member AS 65001, and move R5 out
of the forwarding paths.
Step 6
Move R5 from member AS 100 to member AS 65001, and put R5 back
in the forwarding paths.
Step 7
Update the peering with R5 on R1 and R2.
Step 8
Move R2 out of the forwarding paths, and migrate R2 from member AS
100 to member AS 65000.
Step 9
Step 10
Update the peerings with R2, and put R2 back in the forwarding paths.
Step 11
Move R3 from member AS 100 to member AS 65000.
Step 12
Move R1 from member AS 100 to member AS 65000.
Step 13
Update the peering with R1.
Step 14
Verify BGP reachability for all prefixes.
The following sections illustrate the detailed procedures.
Step 1: Select R4 as the Starting Router and Move It out of the Forwarding Paths
Select the starting router, R4, in the right POP. If R4's BGP configurations are removed,
traffic black-holes if R4 is on the forwarding path. For example, for traffic destined for
192.168.200.0/24 and 172.16.0.0/16 from R6 and R7, a black hole on R4 occurs if the IGP
next hop is R4. To solve the problem, move R4 out of the forwarding path or build tempo-
rary iBGP sessions, as discussed previously. For simplicity, this case study chooses to move
R4 out of the forwarding paths by increasing IS-IS link metrics toward R4.
Example 8-25 shows the Cisco Express Forwarding (CEF) path for 192.168.100.6 (the
BGP next hop for 192.168.201.0/24) on R1 after R4 is moved out of the forwarding paths.
