CCNP / BSCI Exam Tutorial: Route Summarization And also the OSPF Null Interface
CCNP exam achievement, specially about the BSCI exam, needs you understand the details of route summarization. This ability not only necessitates that you've a convenience level with binary conversions, but You will need to know the way and in which to apply route summarization with Each and every individual protocol.
You even have to learn the “side effects” of route summarization. With OSPF, there'll really be an additional interface produced at The purpose of summarization, which catches a lot of CCNP candidates by surprise. Allow’s take a look at the null0 interface And the way it relates to OSPF summarization.
On R1, the next networks are redistributed into OSPF, after which summarized.
interface Loopback16
ip handle 16.sixteen.sixteen.sixteen 255.0.0.0
interface Loopback17
ip tackle 17.17.17.17 255.0.0.0
interface Loopback18
ip handle eighteen.18.eighteen.18 255.0.0.0
interface Loopback19
ip deal with 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute connected subnets
R1(config-router)#summary-handle 16.0.0.0 252.0.0.0
The summary address appears on R2, a downstream router.
R2#present ip route ospf
O E2 sixteen.0.0.0/6 [a hundred and ten/20] by using 172.twelve.123.1, 00:00:05, Serial0
Let’s return to R1 and look at its OSPF table.
R1#demonstrate ip route ospf
O 16.0.0.0/six is really a summary, 00:01:51, Null0
Where by did the null0 interface originate from, and why could it be there? Packets despatched on the null interface are dropped, and In this instance, that’s a superb factor.
Once you configure summary routes in OSPF, a route to null0 will probably be installed into the OSPF routing desk. This helps to stop routing loops. Any packets destined for your routes that were summarized could have a longer match during the routing table, as demonstrated under…
C seventeen.0.0.0/8 is straight related, Loopback17
C 16.0.0.0/8 is instantly linked, Loopback16
C 19.0.0.0/eight is directly related, Loopback19
C eighteen.0.0.0/8 is right related, Loopback18
O sixteen.0.0.0/six is actually 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 significant. OSPF gives us a bit help in that 토토사이트 regard in this situation, and when you research extra complex redistribution scenarios on the strategy to the CCNP and CCIE, you’ll realize that we’ll acquire all the help we could get!