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CCNP / BSCI Exam Tutorial: Route Summarization And The OSPF Null Interface

CCNP Examination success, notably around the BSCI Examination, calls for you understand the main points of route summarization. This ability not only demands that you have a comfort and ease amount with binary conversions, but you have to know the way and the place to use route summarization with Every single particular person protocol.

You also have to understand the “Negative effects” of route summarization. With OSPF, there'll really be an extra interface established at The purpose of summarization, which catches lots of CCNP candidates by surprise. Let’s Examine 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 tackle 16.16.16.16 255.0.0.0

interface Loopback17

ip tackle seventeen.seventeen.seventeen.17 255.0.0.0

interface Loopback18

ip address 18.18.eighteen.eighteen 255.0.0.0

interface Loopback19

ip tackle 19.19.19.19 255.0.0.0

R1(config)#router ospf 1

image

R1(config-router)#redistribute related subnets

R1(config-router)#summary-deal with sixteen.0.0.0 252.0.0.0

The summary address seems on R2, a downstream router.

R2#clearly show 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

Enable’s go back to R1 and check out its OSPF desk.

R1#clearly show ip route ospf

O sixteen.0.0.0/6 is really a summary, 00:01:51, Null0

Wherever did the null0 interface originate from, and why can 먹튀검증 it be there? Packets sent for the null interface are dropped, and In such cases, that’s a superb point.

If you configure summary routes in OSPF, a route to null0 might be set up into your OSPF routing table. This will help to circumvent routing loops. Any packets destined for that routes which have been summarized could have a longer match within the routing table, as demonstrated underneath…

C seventeen.0.0.0/8 is straight linked, Loopback17

C 16.0.0.0/eight is directly connected, Loopback16

C 19.0.0.0/8 is instantly linked, Loopback19

C eighteen.0.0.0/8 is specifically linked, Loopback18

O 16.0.0.0/6 can be a summary, 00:01:fifty one, Null0

.. and packets that don't match among the summarized routes but do match the summary route are going to be dropped.

Preventing routing loops when doing route redistribution and summarization is vital. OSPF presents us a bit help in that regard in this case, and when you analyze a lot more complicated redistribution scenarios on your own way to the CCNP and CCIE, you’ll understand that we’ll take all the help we will get!