BGP Route reflectors are used as an alternate method to full mesh IBGP .
Here R5 ------R2 iBGP
R3------R1 iBGP
R5 RR-1
R2 is RR client
R3—RR2 R1 is RR client
R5 sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*>i
22.22.2.2/32 2.2.2.2 0 100
0 i
*> 55.5.5.5/32 0.0.0.0 0 32768 i
*> 66.6.6.6/32 6.6.6.6 0 0 1.301 i
We can see no route from R1,R3
R3
R3#sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*>i
11.11.1.1/32 1.1.1.1 0 100
0 i
*> 33.3.3.3/32 0.0.0.0 0 32768 i
*> 44.4.4.4/32 4.4.4.4 0 0 201 i
We can see no route from R2,,R5
R2
#sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*> 22.22.2.2/32 0.0.0.0 0 32768 i
*>i
55.5.5.5/32 5.5.5.5 0 100
0 i
* i
66.6.6.6/32 6.6.6.6 0 100 0 65837 i
We can see no route from R1,,R3
R1
#sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*> 11.11.1.1/32 0.0.0.0 0 32768 i
*>i
33.3.3.3/32 3.3.3.3 0 100
0 i
* i
44.4.4.4/32 4.4.4.4 0 100
0 201 i
We can see no route from R1,,R3
…
R3#sh ip bgp
BGP table version is 225, local router ID is 33.3.3.3
Status codes: s suppressed, d damped, h history, * valid,
> best, i - internal,
r
RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
x
best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
*>i
11.11.1.1/32 1.1.1.1 0 100
0 i
*>i
22.22.2.2/32 2.2.2.2 0 100
0 i
*> 33.3.3.3/32 0.0.0.0 0 32768 i
*> 44.4.4.4/32 4.4.4.4 0 0 201 i
*>i
55.5.5.5/32 5.5.5.5 0 100
0 i
*>i 66.6.6.6/32 5.5.5.5 0 100
0 65837 i
R3#
R3#sh ip bgp 22.22.2.2
…………
…………..
Local
2.2.2.2 (metric
156160) from 5.5.5.5 (55.5.5.5)
Origin IGP,
metric 0, localpref 100, valid, internal, best
Originator: 2.2.2.2, Cluster list: 55.5.5.5
rx pathid: 0,
tx pathid: 0x0
R3#
R1#sh ip bgp 22.22.2.2
……….
………..
Originator: 2.2.2.2, Cluster list: 33.3.3.3, 55.5.5.5
rx pathid: 0,
tx pathid: 0x0
R1#
In the above pic R5 & R3 has different cluster –ID …
So prefixes are forwarded .
CLUSTER_LIST Propagation Rules
·
Classic—Before reflecting a route, the RR appends the global
cluster ID to the CLUSTER_LIST. If the received route had no CLUSTER_LIST
attribute, the RR creates a new CLUSTER_LIST attribute with that global cluster
ID.
Loop Prevention Based on
CLUSTER_LIST
·
Classic—When receiving a route, the RR discards the route if the
RR's global cluster ID is contained in the CLUSTER_LIST of the route.
Note – To prevent loop prefixes from same cluster Id will
be discarded.
Now we will configure same cluster Id in both RR.
R3# & R5
router bgp 101
bgp cluster-id
101.101.101.101
R3#sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*>i
11.11.1.1/32 1.1.1.1 0 100
0 i
*> 33.3.3.3/32 0.0.0.0 0 32768 i
*> 44.4.4.4/32 4.4.4.4 0 0 201 i
*>i
55.5.5.5/32 5.5.5.5 0
100 0 i
*>i
66.6.6.6/32 5.5.5.5 0 100
0 65837 i
R3#
In above
example there is no route from R2 because it is from same cluster
101.101.101.101
same in r1
Network Next Hop Metric LocPrf Weight Path
*> 11.11.1.1/32 0.0.0.0 0 32768 i
*>i 33.3.3.3/32 3.3.3.3 0 100 0 i
* i 44.4.4.4/32 4.4.4.4 0 100 0 201 i
*>i 55.5.5.5/32 5.5.5.5 0 100 0 i
*>i 66.6.6.6/32 5.5.5.5 0 100 0 1.301 i
No route from R2
When EBGP prefix is advertised to iBGP peer, No cluster list attribute is on update.
Like in R5 for 44.4.4.4 ( EBGP route )
R5#sh ip bgp 44.4.4.4
BGP routing table entry for 44.4.4.4/32, version 32
........
3.3.3.3 (metric 158720) from 3.3.3.3 (33.3.3.3)
Origin IGP, metric 0, localpref 100, valid, internal, best
rx pathid: 0, tx pathid: 0x0
R5#
R2#sh ip bgp 44.4.4.4
BGP routing table entry for 44.4.4.4/32, version 323
........
3.3.3.3 (metric 156160) from 5.5.5.5 (55.5.5.5)
Origin IGP, metric 0, localpref 100, valid, internal, best
Originator: 33.3.3.3, Cluster list: 101.101.101.101
When EBGP prefix is advertised to iBGP peer, No cluster list attribute is on update.
Like in R5 for 44.4.4.4 ( EBGP route )
R5#sh ip bgp 44.4.4.4
BGP routing table entry for 44.4.4.4/32, version 32
........
3.3.3.3 (metric 158720) from 3.3.3.3 (33.3.3.3)
Origin IGP, metric 0, localpref 100, valid, internal, best
rx pathid: 0, tx pathid: 0x0
R5#
but same route can be advertised to R2 as RR client because this is not a internal route or same cluster ID.
R2#sh ip bgp 44.4.4.4
BGP routing table entry for 44.4.4.4/32, version 323
........
3.3.3.3 (metric 156160) from 5.5.5.5 (55.5.5.5)
Origin IGP, metric 0, localpref 100, valid, internal, best
Originator: 33.3.3.3, Cluster list: 101.101.101.101
in R3
router bgp 101
bgp asnotation dot
bgp acluster-id 101.101.101.100
R5#sh ip bgp
*>i 11.11.1.1/32 1.1.1.1 0 100 0 i
*>i 22.22.2.2/32 2.2.2.2 0 100 0 i
*>i 33.3.3.3/32 3.3.3.3 0 100 0 i
*>i 44.4.4.4/32 3.3.3.3 0 100 0 201 i
*> 55.5.5.5/32 0.0.0.0 0 32768 i
*> 66.6.6.6/32 6.6.6.6 0 0 1.301 i
BGP routing table entry for 11.11.1.1/32, version 344
Paths: (1 available, best #1, table default)
Not advertised to any peer
Refresh Epoch 1
Local
1.1.1.1 (metric 158720) from 5.5.5.5 (55.5.5.5)
Origin IGP, metric 0, localpref 100, valid, internal, best
Originator: 1.1.1.1, Cluster list: 101.101.101.100, 101.101.101.101
rx pathid: 0, tx pathid: 0x0
R2#
No comments:
Post a Comment