CCNP / BSCI Examination Tutorial: Route Summarization As well as the OSPF Null Interface
CCNP exam achievement, especially on the BSCI exam, needs you have an understanding of the main points of route summarization. This talent not simply demands you have a comfort and ease amount with binary conversions, but You must know how and where by to apply route summarization with each unique protocol.
You also have to grasp the “Unintended effects” of route summarization. With OSPF, there will basically be an extra interface established at The purpose of summarization, and this catches a lot of CCNP candidates unexpectedly. Permit’s Look into the null0 interface And just how it pertains to OSPF summarization.
On R1, the following networks are redistributed into OSPF, after which you can summarized.
interface Loopback16
ip deal with sixteen.16.sixteen.16 255.0.0.0
interface Loopback17
ip tackle seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip handle eighteen.18.eighteen.eighteen 255.0.0.0
interface Loopback19
ip address 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 handle 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.twelve.123.1, 00:00:05, Serial0
Let’s go back to R1 and take a look at its OSPF table.
R1#present ip route ospf
O 16.0.0.0/six is really a summary, 00:01:51, Null0
Where did the null0 interface come from, and why can it be there? Packets despatched to the null interface are dropped, and in this case, that’s a good thing.
If you configure summary routes in OSPF, a path to null0 will likely be installed in the OSPF routing table. This allows to prevent routing loops. Any packets destined for your routes which were summarized should have an extended match from the routing desk, as proven below…
C 17.0.0.0/eight is immediately linked, Loopback17
C 16.0.0.0/8 is straight linked, Loopback16
C 19.0.0.0/8 is right connected, Loopback19
C 18.0.0.0/eight is right related, Loopback18
O 16.0.0.0/6 is actually a summary, 00:01:51, Null0
.. and packets that don't match one of the summarized routes but do match the summary route will be dropped.
Stopping routing loops when carrying out route redistribution and summarization is vital. OSPF gives us a bit assist in that regard in this example, and while you examine much more advanced redistribution eventualities in 먹튀 your approach to the CCNP and CCIE, you’ll recognize that we’ll get all the assistance we may get!