JNCIP part 6

The tricky JNCIP ibgp requirement :

• You must configure at least three clusters and at least two route reflectors.

• You must use physical address peering in at least one of your clusters.

• The failure of any link must not break the route reflection topology.

• The route reflection topology must not impose suboptimal routing or black holes.

• Authentication and logging settings from the previous section must remain in effect.

The ebook indicate the r3, r4 will in different cluster because :

But placing both r3 and r4 in the same cluster would be a mistake in this case,

because doing so will cause r3 and r4 to ignore updates that carry their common cluster ID.

This will result in missing routes on one of the reflectors should a peering interface fail on

one of the two route reflectors that serve clients r1 or r2,

which would violate the redundancy aspects of your design requirements.


I'll show you why.

If both R3 and R4 in the same cluster 1.1.1.1 and R2 to R4 interface is down.
R4 BGP peering to r2 and r1 is gone, and both r1,r2 send BGP update to r3, then r3 will update to r4. When R4 received BGP update from R3, R4 will not accept "because r3,r4 in the same cluster"


A Destination P Prf Metric 1 Metric 2 Next hop AS path
* 192.168.50.0/24 B 170 100 >10.0.2.9 I

iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)

R4 will get missing route. This result will make you score 0 point.