CCNP / BSCI Examination Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP exam success, significantly over the BSCI Test, needs you fully grasp the main points of route summarization. This ability not simply requires you have a comfort and ease level with binary conversions, but you have to know how and wherever to apply route summarization with each person protocol.
You even have to understand the “Negative effects” of route summarization. With OSPF, there'll basically be an extra interface created at The purpose of summarization, which catches many CCNP candidates unexpectedly. Let’s take a look at the null0 interface And exactly how it pertains to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, and after that summarized.
interface Loopback16
ip deal with sixteen.16.16.16 255.0.0.0
interface Loopback17
ip deal with 17.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip address 18.eighteen.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-address sixteen.0.0.0 252.0.0.0
The summary address appears on R2, a downstream router.
R2#display ip route ospf
O E2 16.0.0.0/six [a hundred and ten/twenty] by way of 172.12.123.one, 00:00:05, Serial0
Enable’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 come from, and why is it there? Packets despatched on the null interface are dropped, and in this case, that’s a fantastic point.
When you configure summary routes in OSPF, a path to null0 will be put in into your OSPF routing desk. This helps to stop routing loops. Any packets destined for your routes which have been summarized will likely have a longer match inside the routing desk, as revealed under…
C 17.0.0.0/eight is right related, Loopback17
C sixteen.0.0.0/8 is directly related, Loopback16
C 19.0.0.0/8 is right related, Loopback19
C eighteen.0.0.0/eight is immediately related, Loopback18
O 16.0.0.0/6 can be a summary, 00:01:fifty one, Null0
.. and packets that don't match one of the summarized routes but do match the summary route will be dropped.
Blocking routing loops when accomplishing route redistribution and summarization is significant. OSPF offers us a little help in that regard 먹튀 in this situation, and as you analyze a lot more sophisticated redistribution situations in your technique to the CCNP and CCIE, you’ll understand that we’ll acquire all the assistance we could possibly get!