CCNP / BSCI Examination Tutorial: Route Summarization And The OSPF Null Interface
CCNP exam results, notably on the BSCI Test, requires you comprehend the small print of route summarization. This talent don't just demands that you have a comfort amount with binary conversions, but You need to know the way and wherever to use route summarization with each personal protocol.
You also have to find out the “Uncomfortable side effects” of route summarization. With OSPF, there will actually be an additional interface created at The purpose of summarization, and this catches many CCNP candidates without warning. Let’s Examine the null0 interface And exactly how it relates to OSPF summarization.
On R1, the following networks are redistributed into OSPF, and then summarized.
interface Loopback16
ip deal with 16.16.16.16 255.0.0.0
interface Loopback17
ip tackle 17.17.17.17 255.0.0.0
interface Loopback18
ip deal with eighteen.18.eighteen.eighteen 255.0.0.0
interface Loopback19
ip handle 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute related subnets
R1(config-router)#summary-deal with 16.0.0.0 252.0.0.0
The summary tackle appears on R2, a downstream router.
R2#show ip route ospf
O E2 sixteen.0.0.0/6 [one hundred ten/twenty] by way of 172.12.123.1, 00:00:05, Serial0
Allow’s return to R1 and look at its OSPF desk.
R1#display ip route ospf
O sixteen.0.0.0/six is really a summary, 00:01:51, Null0
Where did the null0 interface originate from, and why can it be there? Packets despatched for the null interface are dropped, and In such cases, that’s a great issue.
Whenever you configure summary routes in OSPF, a path to null0 will likely be set up into the OSPF routing desk. This helps to avoid routing loops. Any packets destined for your routes that were summarized could have an extended match while in the routing desk, as revealed below…
C 17.0.0.0/8 is specifically 먹튀검증 linked, Loopback17
C sixteen.0.0.0/8 is directly connected, Loopback16
C 19.0.0.0/8 is right linked, Loopback19
C 18.0.0.0/eight is right related, Loopback18
O 16.0.0.0/6 is usually a summary, 00:01:fifty one, Null0
.. and packets that do not match among the list of summarized routes but do match the summary route will be dropped.
Stopping routing loops when undertaking route redistribution and summarization is vital. OSPF gives us a little bit assist in that regard in this situation, and while you review far more elaborate redistribution eventualities with your approach to the CCNP and CCIE, you’ll know that we’ll acquire all the assistance we will get!