CCNP / BSCI Examination Tutorial: Route Summarization As well as the OSPF Null Interface
CCNP Test results, especially within the BSCI exam, needs you realize the small print of route summarization. This ability not simply involves that you've a consolation level with binary conversions, but You must know the way and where by to apply route summarization with Every single particular person protocol.
You even have to find out the “Unwanted side effects” of route summarization. With OSPF, there'll basically be an extra interface created at The purpose of summarization, and this catches a great deal of CCNP candidates by surprise. Allow’s Check out the null0 interface And exactly how it pertains to OSPF summarization.
On R1, the following networks are redistributed into OSPF, after which you can summarized.
interface Loopback16
ip deal with sixteen.16.16.sixteen 255.0.0.0
interface Loopback17
ip deal with 17.17.17.seventeen 255.0.0.0
interface Loopback18
ip tackle eighteen.eighteen.18.18 255.0.0.0
interface Loopback19
ip address 토토사이트 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-deal with sixteen.0.0.0 252.0.0.0
The summary deal with seems on R2, a downstream router.
R2#clearly show ip route ospf
O E2 16.0.0.0/six [a hundred and ten/twenty] by means of 172.12.123.1, 00:00:05, Serial0
Enable’s go back to R1 and look at its OSPF desk.
R1#demonstrate ip route ospf
O 16.0.0.0/6 is actually a summary, 00:01:51, Null0
Exactly where did the null0 interface come from, and why could it be there? Packets despatched to your null interface are dropped, and In cases like this, that’s a fantastic detail.
If you configure summary routes in OSPF, a path to null0 will be put in into the OSPF routing table. This can help to forestall routing loops. Any packets destined for that routes that were summarized should have an extended match from the routing desk, as proven down below…
C 17.0.0.0/eight is directly related, Loopback17
C sixteen.0.0.0/8 is specifically connected, Loopback16
C 19.0.0.0/8 is immediately connected, Loopback19
C 18.0.0.0/eight is directly connected, Loopback18
O sixteen.0.0.0/six is a summary, 00:01:51, Null0
.. and packets that don't match among the summarized routes but do match the summary route will likely be dropped.
Blocking routing loops when performing route redistribution and summarization is important. OSPF gives us slightly assist in that regard in this situation, and when you research far more advanced redistribution eventualities in your method to the CCNP and CCIE, you’ll understand that we’ll take all the help we can get!