CCNP / BSCI Examination Tutorial: Route Summarization As well as OSPF Null Interface
CCNP exam achievement, specially within the BSCI Examination, needs you recognize the main points of route summarization. This talent not just requires that you have a consolation amount with binary conversions, but You will need to understand how and exactly where to apply route summarization with Each individual particular person protocol.
You even have to learn the “side effects” of route summarization. With OSPF, there will in fact be an extra interface designed at the point of summarization, which catches a great deal of CCNP candidates by surprise. Enable’s Check out the null0 interface And exactly how it pertains to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, and after that summarized.
interface Loopback16
ip deal with sixteen.sixteen.16.sixteen 255.0.0.0
interface Loopback17
ip deal with seventeen.17.17.17 255.0.0.0
interface Loopback18
ip deal with eighteen.eighteen.eighteen.eighteen 255.0.0.0
interface Loopback19
ip handle 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute connected subnets
R1(config-router)#summary-tackle 16.0.0.0 252.0.0.0
The summary deal with seems on R2, a downstream router.
R2#show ip route ospf
O E2 sixteen.0.0.0/6 [110/20] via 172.12.123.one, 00:00:05, Serial0
Enable’s return to R1 and check out its OSPF table.
R1#clearly show ip route ospf
O sixteen.0.0.0/6 can be a summary, 00:01:51, Null0
Where did the null0 interface come from, and why can it be there? Packets sent to the null interface are dropped, and In this instance, that’s a fantastic detail.
If you configure summary routes in 토토사이트 OSPF, a path to null0 might be put in into your OSPF routing table. This will help to forestall routing loops. Any packets destined for that routes which have been summarized will likely have an extended match from the routing table, as demonstrated down below…
C 17.0.0.0/8 is immediately related, Loopback17
C sixteen.0.0.0/8 is specifically related, Loopback16
C 19.0.0.0/8 is instantly linked, Loopback19
C eighteen.0.0.0/eight is immediately connected, Loopback18
O sixteen.0.0.0/six is a summary, 00:01:51, Null0
.. and packets that do not match one of several summarized routes but do match the summary route will likely be dropped.
Blocking routing loops when executing route redistribution and summarization is vital. OSPF provides us a bit help in that regard in this case, and while you examine additional advanced redistribution eventualities on your strategy to the CCNP and CCIE, you’ll know that we’ll choose all the help we might get!