CCNP / BSCI Examination Tutorial: Route Summarization Plus the OSPF Null Interface
CCNP Test accomplishment, specially to the BSCI exam, demands you understand the small print of route summarization. This ability not just requires that you've got a ease and comfort level with binary conversions, but You will need to know how and where to use route summarization with Each individual person protocol.
You also have to understand the “Negative effects” of route summarization. With OSPF, there'll in fact be an additional interface developed at The purpose of summarization, which catches many CCNP candidates without warning. Enable’s Check out the null0 interface And just how it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, and afterwards summarized.
interface Loopback16
ip handle sixteen.sixteen.16.sixteen 255.0.0.0
interface Loopback17
ip tackle 17.17.17.seventeen 255.0.0.0
interface Loopback18
ip handle eighteen.eighteen.18.18 255.0.0.0
interface 먹튀검증 Loopback19
ip address 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-tackle 16.0.0.0 252.0.0.0
The summary handle appears on R2, a downstream router.
R2#present ip route ospf
O E2 sixteen.0.0.0/6 [a hundred and ten/twenty] by means of 172.12.123.one, 00:00:05, Serial0
Allow’s return to R1 and evaluate its OSPF desk.
R1#show ip route ospf
O 16.0.0.0/6 is often a summary, 00:01:51, Null0
The place did the null0 interface originate from, and why could it be there? Packets sent towards the null interface are dropped, and In such cases, that’s a great thing.
If you configure summary routes in OSPF, a route to null0 is going to be mounted in to the OSPF routing table. This aids to forestall routing loops. Any packets destined with the routes that have been summarized should have a longer match in the routing table, as revealed below…
C seventeen.0.0.0/8 is straight linked, Loopback17
C 16.0.0.0/8 is directly related, Loopback16
C 19.0.0.0/eight is instantly connected, Loopback19
C 18.0.0.0/8 is instantly connected, Loopback18
O 16.0.0.0/6 is often a summary, 00:01:51, Null0
.. and packets that do not match one of several summarized routes but do match the summary route is going to be dropped.
Preventing routing loops when executing route redistribution and summarization is important. OSPF presents us a bit assist in that regard in this case, and while you research far more complicated redistribution situations in your way to the CCNP and CCIE, you’ll understand that we’ll just take all the help we may get!