CCNP / BSCI Exam Tutorial: Route Summarization Plus the OSPF Null Interface
CCNP Examination achievements, especially over the BSCI Test, calls for you comprehend the small print of route summarization. This skill don't just involves that you have a comfort degree with binary conversions, but you have to know the way and exactly where to use route summarization with Just about every person protocol.
You also have to find out the “Negative effects” of route summarization. With OSPF, there'll truly be an additional interface established at the point of summarization, which catches a lot of CCNP candidates abruptly. Allow’s Consider the null0 interface And the way it relates to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, and then summarized.
interface Loopback16
ip deal with 16.sixteen.sixteen.sixteen 255.0.0.0
interface Loopback17
ip deal with seventeen.seventeen.seventeen.17 255.0.0.0
interface Loopback18
ip handle eighteen.eighteen.eighteen.18 255.0.0.0
interface Loopback19
ip tackle 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute related subnets
R1(config-router)#summary-tackle 16.0.0.0 252.0.0.0
The summary deal with appears on R2, a downstream router.
R2#display ip route ospf
O E2 sixteen.0.0.0/6 [a hundred and ten/20] by way of 172.12.123.1, 00:00:05, Serial0
Enable’s go back to R1 and look at its OSPF desk.
R1#clearly show ip route ospf
O 16.0.0.0/six is often a summary, 00:01:51, Null0
Exactly where did the null0 interface originate from, and why is it there? Packets despatched to your null interface are dropped, and in this case, that’s an excellent matter.
Once you configure summary 먹튀검증 routes in OSPF, a path to null0 is going to be mounted to the OSPF routing table. This aids to circumvent routing loops. Any packets destined with the routes that have been summarized may have a longer match from the routing table, as demonstrated beneath…
C seventeen.0.0.0/8 is immediately linked, Loopback17
C sixteen.0.0.0/eight is right related, Loopback16
C 19.0.0.0/8 is immediately linked, Loopback19
C eighteen.0.0.0/8 is instantly linked, Loopback18
O sixteen.0.0.0/six is really a summary, 00:01:fifty one, Null0
.. and packets that don't match one of several summarized routes but do match the summary route will probably be dropped.
Stopping routing loops when performing route redistribution and summarization is important. OSPF gives us a little help in that regard in this example, and while you examine more complicated redistribution eventualities on the approach to the CCNP and CCIE, you’ll recognize that we’ll acquire all the assistance we could possibly get!