BGP Routing Configuration 6 Points

After finishing this section, make sure that all configured interfaces and subnets are consistently visible on all pertinent routers, even in the event of network failure of any one router.

Basic IBGP Configuration

Configure IBGP on all routers in your network:

■ Do not use any WAN IP interfaces for IBGP sessions, because your network is prone to failures across the Frame Relay cloud.

■ Configure R4 as the route reflector and ensure that remote routers peer to R4 only.

■ Minimize IBGP configurations as much as possible.

■ The IBGP connection between R2 and R4 must use MD5 authentication to authenticate the IBGP peer.

■ You can disable BGP synchronization.

■ As long as there is IP connectivity in your network, ensure that BGP is active in all routers.

■ Using the network command only, make sure only the loopback interfaces on Routers R1 through R5 are advertised by BGP to the route reflector, R4. Ensure that each router has a corresponding BGP table entry for all loopbacks.

■ Do not change the BGP administrative distance to complete this task.

■ Make sure you have full IBGP connectivity.

■ Ensure that all routers have BGP routing entries in their respective BGP tables.

NOTE R4's BGP table (not IP routing table) should look like this: R4#show ip bgp

BGP table version is 11, local router ID is 144.254.154.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete

NOTE R4's BGP table (not IP routing table) should look like this: R4#show ip bgp

BGP table version is 11, local router ID is 144.254.154.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete

Network

Next Hop

Metric

LocPrf

Weight

Path

*>i144.254.

151 ,

,0/24

144.254.151.1

0

100

0

i

*>i144.254.

152.

,0/24

144.254.152.1

0

100

0

i

*>i144.254.

153,

,0/24

144.254.153.1

0

100

0

i

*> 144.254.

154,

,0/24

0.0.0.0

0

32768

i

Basic IBGP Configuration Solution

Router R4, the hub of this network, provides BGP (internal) information to R1, R2, R3, and R5.

Example 8-64 configures R4 as the route reflector to remote peers R1, R2, R3, and R5 using the loopback interface as the source address. Next-hop address could be used, but in the event of a

WAN failure (in particular for R3), the BGP session would be inactive, so it is better to use the loopback.

Example 8-64 IBGP Configuration on R4

router bgp 333

no synchronization

network 144.254.154.0

mask 255.255.255.0

neighbor

144

254

151

1

remote-as 333

neighbor

144

254

151

1

update-source Loopback0

neighbor

144

254

151

1

route - reflector-client

neighbor

144

254

152

1

remote-as 333

neighbor

144

254

152

1

password cisco

neighbor

144

254

152

1

update-source Loopback0

neighbor

144

254

152

1

route-reflector-client

neighbor

144

254

153

1

remote-as 333

neighbor

144

254

153

1

update-source Loopback0

neighbor

144

254

153

1

route-reflector-client

neighbor

144

254

155

1

remote-as 333

neighbor

144

254

155

1

update-source Loopback0

neighbor

144

.254

.155.1 route-reflector-client

R4 is configured as the route reflector to four remote routers in AS 333. Notice that MD5 authentication is enabled between R4 and R2, as stated in the question criteria. The network command is used to inject Loopback 0 on R4 into the BGP routing table.

Example 8-65 enables IBGP on R2 with MD5 authentication to R4.

Example 8-65 IBGP Configuration on R2

router bgp 333

no synchronization

network 144.254.152.0

mask 255.255.255.

0

neighbor 144.254.154.1

remote-as 333

neighbor 144.254.154.1

password cisco

neighbor 144.254.154.

1 update-source

Loopback0

R2 is configured as an IBGP peer to R4 with MD5 authentication to ensure that the IBGP session is authenticated. The network command is used to inject the loopback of R2 into the BGP table.

Example 8-66 confirms the BGP table on R2 with the command show ip bgp.

Example 8-66 show ip bgp on R2

R2#show ip bgp

BGP table version is 22, local router ID is 144.254.152.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Example 8-66 show ip bgp on R2 (Continued)

Network

Next Hop

Metric

LocPrf

Weight

Path

*>i144.254.

.151.

0/24

144.254.151.1

0

100

0

i

*> 144.254.

.152.

0/24

0.0.0.0

0

32768

i

*>i144.254.

.153.

0/24

144.254.153.1

0

100

0

i

*>i144.254.

.154.

0/24

144.254.154.1

0

100

0

i

*>i144.254.

.155.

0/24

144.254.155.1

0

100

0

i

Example 8-67 confirms the BGP table on R4 with the command show ip bgp.

Example 8-67 show ip bgp on R4

R4#show ip bgp

BGP table version is 14, local router ID is 144.254.154.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*>i144.

.254.

.151.

0/

144.

.254.

151.1

0

100

0

i

*>i144.

.254.

.152.

0/24

144.

.254.

152.1

0

100

0

i

*>i144.

.254.

.153.

0/24

144.

.254.

153.1

0

100

0

i

*> 144.

.254.

.154.

0/

0.0.

0.0

0

32768

i

*>i144.

.254.

.155.

0/

144.

.254.

155.1

0

100

0

i

Example 8-68 confirms the IBGP on R4, as established with the summary BGP command show ip bgp summary.

Example 8-68 show ip bgp summary on R4 R4#show ip bgp summary

BGP router identifier 144.254.154.1, local AS number 333 BGP table version is 14, main routing table version 14 5 network entries and 5 paths using 665 bytes of memory 2 BGP path attribute entries using 120 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP activity 8/31 prefixes, 8/3 paths, scan interval 15 secs

Neighbor

V

AS

MsgRcvd

MsgSent

TblVer

InQ

OutQ

Up/Down

State/PfxRcd

144.254.151.1

4

333

14192

14204

14

0

0

1w2d

1

144.254.152.1

4

333

14191

14202

14

0

0

1w2d

1

144.254.153.1

4

333

14189

14198

14

0

0

1w2d

1

144.254.155.1

4

333

14189

14199

14

0

0

1w2d

1

Five networks are installed in the BGP table, one local (next hop 0.0.0.0) and four remote (next hops for R1, R2, R3, and R5 loopback IP addresses).

NOTE For more examples of CCIE questions on BGP, refer to Appendix C for a sample Routing and Switching lab endorsed by the CCIE content management team.

You will notice that the Routing and Switching topics presented in the first half of this lab are valued at approximately half of the points (56 points). The next section is based on Security features and is also valued at approximately half of the points (44 points). As you can see, a candidate weak in Routing and Switching but proficient in Security features or vice versa will still likely fail because a total of 80 points is needed to pass.

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