CCNP / BSCI Test Tutorial: Route Summarization And The OSPF Null Interface
CCNP Examination results, particularly on the BSCI exam, needs you have an understanding of the small print of route summarization. This talent don't just involves you have a comfort amount with binary conversions, but It's important to understand how and exactly where to use route summarization with each unique protocol.
You even have to know the “Unwanted side effects” of route summarization. With OSPF, there will actually be an extra interface made at The purpose of summarization, and this catches a lot of CCNP candidates abruptly. Let’s take a 토토사이트 look at the null0 interface And the way it relates to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, after which you can summarized.
interface Loopback16
ip address sixteen.sixteen.sixteen.sixteen 255.0.0.0
interface Loopback17
ip deal with seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip handle 18.eighteen.18.eighteen 255.0.0.0
interface Loopback19
ip address 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute connected subnets
R1(config-router)#summary-tackle sixteen.0.0.0 252.0.0.0
The summary handle seems on R2, a downstream router.
R2#clearly show ip route ospf
O E2 sixteen.0.0.0/6 [one hundred ten/twenty] via 172.twelve.123.one, 00:00:05, Serial0
Enable’s return to R1 and look at its OSPF desk.
R1#show ip route ospf
O 16.0.0.0/6 is really a summary, 00:01:fifty one, Null0
The place did the null0 interface originate from, and why could it be there? Packets sent for the null interface are dropped, and In such a case, that’s an excellent matter.
Any time you configure summary routes in OSPF, a path to null0 are going to be installed into the OSPF routing desk. This assists to circumvent routing loops. Any packets destined for your routes which were summarized can have a longer match while in the routing desk, as demonstrated down below…
C 17.0.0.0/eight is directly connected, Loopback17
C sixteen.0.0.0/8 is right connected, Loopback16
C 19.0.0.0/eight is immediately related, Loopback19
C eighteen.0.0.0/8 is instantly linked, Loopback18
O sixteen.0.0.0/six can be a summary, 00:01:fifty one, Null0
.. and packets that do not match on the list of summarized routes but do match the summary route is going to be dropped.
Blocking routing loops when carrying out route redistribution and summarization is significant. OSPF offers us slightly assist in that regard in this example, and when you research additional complex redistribution eventualities on the strategy to the CCNP and CCIE, you’ll know that we’ll take all the assistance we might get!