CCNP / BSCI Exam Tutorial: Route Summarization Plus the OSPF Null Interface
CCNP Examination accomplishment, significantly on the BSCI Examination, demands you understand the small print of route summarization. This ability not just calls for you have a ease and comfort stage with binary conversions, but It's important to know the way and where by to use route summarization with each individual protocol.
You also have to grasp the “Uncomfortable 먹튀검증 side effects” of route summarization. With OSPF, there will in fact be an extra interface created at The purpose of summarization, and this catches a lot of CCNP candidates by surprise. Enable’s take a look at the null0 interface And exactly how it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, then summarized.
interface Loopback16
ip tackle sixteen.sixteen.sixteen.16 255.0.0.0
interface Loopback17
ip address seventeen.17.seventeen.seventeen 255.0.0.0
interface Loopback18
ip handle 18.18.18.18 255.0.0.0
interface Loopback19
ip deal with 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-handle sixteen.0.0.0 252.0.0.0
The summary tackle appears on R2, a downstream router.
R2#demonstrate ip route ospf
O E2 16.0.0.0/6 [110/20] by way of 172.twelve.123.one, 00:00:05, Serial0
Allow’s return to R1 and take a look at its OSPF table.
R1#show ip route ospf
O 16.0.0.0/6 is a summary, 00:01:fifty one, Null0
Wherever did the null0 interface originate from, and why is it there? Packets despatched towards the null interface are dropped, and In this instance, that’s a fantastic detail.
After you configure summary routes in OSPF, a path to null0 is going to be mounted in to the OSPF routing desk. This can help to circumvent routing loops. Any packets destined for your routes that have been summarized will likely have an extended match during the routing desk, as demonstrated under…
C seventeen.0.0.0/8 is instantly related, Loopback17
C sixteen.0.0.0/8 is directly related, Loopback16
C 19.0.0.0/8 is instantly related, Loopback19
C eighteen.0.0.0/8 is immediately linked, Loopback18
O sixteen.0.0.0/6 is actually a summary, 00:01:51, Null0
.. and packets that do not match among the summarized routes but do match the summary route will be dropped.
Preventing routing loops when accomplishing route redistribution and summarization is important. OSPF provides us a little bit assist in that regard in this example, and as you review more sophisticated redistribution situations in your technique to the CCNP and CCIE, you’ll recognize that we’ll acquire all the assistance we could possibly get!