Routers R5, R2 and R6 are all IBGP peers with R2 configured as the Route
Reflector. R5 has an EBGP peering to R4 and R6 has an EBGP peering to R9
R5-IBGP-R2-IBGP-R6
| |
EBGP EBGP
| |
R4 r9
In this task R4 in AS4 is advertising the following loopbacks into BGP over to
R5 in AS 256 (EBGP)
Network Next Hop Metric LocPrf Weight Path
*> 204.40.4.4/32 0.0.0.0 0 32768 i
*> 204.41.4.4/32 0.0.0.0 0 32768 i
*> 204.42.4.4/32 0.0.0.0 0 32768 i
*> 204.43.4.4/32 0.0.0.0 0 32768 i
The task says to configure R5 so that R2 and R6 only see the loopbacks with
even numbers in the second octet. I configured everything up and set the
community to no-export for the even numbered routes (204.40 && 204.32) and they
are being sent over to R2 just as we would expect them to. If I look at the
routes I see they are tagged with "no-export" on R2 and R6, however they are
still showing up in R9's BGP table, but how come?
Here are some of the relevant config
R5(config)#do sh run | s bgp
router bgp 256
no synchronization
bgp log-neighbor-changes
aggregate-address 204.40.0.0 255.252.0.0 suppress-map LOSE-THESE
neighbor 2.2.2.2 remote-as 256
neighbor 2.2.2.2 update-source Loopback1
neighbor 2.2.2.2 send-community
neighbor 2.2.2.2 route-map TAG-THESE out
neighbor 4.4.4.4 remote-as 4
neighbor 4.4.4.4 ebgp-multihop 2
neighbor 4.4.4.4 update-source Loopback1
no auto-summary
access-list 52 permit 204.40.4.4 0.2.0.0
route-map TAG-THESE permit 10
match ip address 52
set community no-export
route-map FOR-R2 permit 20
R2(config)#do sh run | s bgp
router bgp 256
no synchronization
bgp log-neighbor-changes
neighbor 5.5.5.5 remote-as 256
neighbor 5.5.5.5 update-source Loopback1
neighbor 5.5.5.5 route-reflector-client
neighbor 6.6.6.6 remote-as 256
neighbor 6.6.6.6 update-source Loopback1
neighbor 6.6.6.6 route-reflector-client
neighbor 6.6.6.6 send-community
no auto-summary
Over on R6 we can see the routes are tagged with "no-community"
R6(config)#do sh ip bgp 204.40.4.4
BGP routing table entry for 204.40.4.4/32, version 4
Paths: (1 available, best #1, table Default-IP-Routing-Table, not advertised to
EBGP peer)
Flag: 0x820
Not advertised to any peer
4
4.4.4.4 (metric 20) from 2.2.2.2 (2.2.2.2)
Origin IGP, metric 0, localpref 100, valid, internal, best
Community: no-export
Originator: 5.5.5.5, Cluster list: 2.2.2.2
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