CCNP / BSCI Examination Tutorial: Route Summarization Plus the OSPF Null Interface
CCNP exam success, specially over the BSCI Examination, demands you fully grasp the details of route summarization. This ability not simply needs you have a ease and comfort degree with binary conversions, but It's important to know how and where to use route summarization with Each individual particular person protocol.
You even have to be aware of the “Uncomfortable side effects” of route summarization. With OSPF, there'll in fact be an extra interface designed at the point of summarization, and this catches many CCNP candidates unexpectedly. Permit’s Check out the null0 interface And exactly how it relates to OSPF summarization.
On R1, the following networks are redistributed into OSPF, and afterwards summarized.
interface Loopback16
ip deal with 16.sixteen.16.16 255.0.0.0
interface Loopback17
ip deal with 17.17.seventeen.17 255.0.0.0
interface Loopback18
ip handle eighteen.eighteen.eighteen.eighteen 255.0.0.0
interface Loopback19
ip deal with 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute connected subnets
R1(config-router)#summary-deal with 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/six [a hundred and ten/twenty] by way of 172.twelve.123.one, 00:00:05, Serial0
Allow’s go back to R1 and examine its OSPF desk.
R1#exhibit ip route ospf
O sixteen.0.0.0/6 is really a summary, 00:01:51, Null0
In which did the null0 interface come from, and why could it be there? Packets despatched to your null interface are dropped, and In such cases, that’s a great factor.
Whenever you configure summary routes in OSPF, a path to null0 will likely be set up in the OSPF routing table. This helps to circumvent routing loops. Any packets destined for the routes that have been summarized may have an extended match in the routing desk, as shown underneath…
C 17.0.0.0/eight is specifically linked, Loopback17
C 16.0.0.0/eight is straight connected, Loopback16
C 19.0.0.0/8 is specifically related, Loopback19
C eighteen.0.0.0/8 is right related, Loopback18
O sixteen.0.0.0/6 is often a summary, 00:01:51, Null0
.. and packets that don't match among the summarized routes but do match the summary route will likely be dropped.
Protecting against routing loops when accomplishing route redistribution and summarization is important. OSPF offers us slightly assist in that regard in this example, and while you 먹튀검증 research additional sophisticated redistribution eventualities on the technique to the CCNP and CCIE, you’ll know that we’ll choose all the help we may get!