CCNP / BSCI Examination Tutorial: Route Summarization And The OSPF Null Interface
CCNP exam achievements, particularly within the BSCI Test, demands you fully grasp the small print of route summarization. This ability not merely needs that you've got a comfort and ease degree with binary conversions, but You need to know how and exactly where to use route summarization with Every single particular person protocol.
You even have to find out the “side effects” of route summarization. With OSPF, there will in fact be an extra interface designed at the point of summarization, which catches many CCNP candidates by surprise. Enable’s take a look at the null0 interface And just how it relates to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, and then summarized.
interface Loopback16
ip address 16.sixteen.16.sixteen 255.0.0.0
interface Loopback17
ip handle seventeen.seventeen.17.17 255.0.0.0
interface Loopback18
ip tackle eighteen.18.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 sixteen.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#display ip route ospf
O E2 16.0.0.0/six [110/twenty] through 172.12.123.1, 00:00:05, Serial0
Enable’s return to R1 and take a look at its OSPF desk.
R1#show ip route ospf
O 16.0.0.0/6 is really a summary, 00:01:51, Null0
The place did the null0 interface come from, and why can it be there? Packets sent for the null interface are dropped, and In such a case, that’s a good issue.
Whenever you configure summary routes in OSPF, a route to null0 is going to be set up to the OSPF routing desk. This helps to avoid routing loops. Any packets destined for your routes that have been summarized will have an extended match while in the routing table, as demonstrated beneath…
C seventeen.0.0.0/8 is specifically related, Loopback17
C 16.0.0.0/eight is immediately linked, Loopback16
C 19.0.0.0/8 is specifically related, Loopback19
C eighteen.0.0.0/eight is immediately related, Loopback18
O 16.0.0.0/six is actually 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 are going to be dropped.
Avoiding routing loops when performing route redistribution and summarization is vital. OSPF offers us somewhat help in that regard in this example, and when you analyze a lot more intricate redistribution situations on your own approach 토토사이트 to the CCNP and CCIE, you’ll realize that we’ll get all the assistance we could possibly get!