CCNP / BSCI Test Tutorial: Route Summarization And also the OSPF Null Interface
CCNP Examination success, specially on the BSCI exam, calls for you have an understanding of the details of route summarization. This talent not just requires that you've a consolation stage with binary conversions, but You will need to know how and exactly where to apply route summarization with Each and every specific protocol.
You even have to know the “Uncomfortable side effects” of route summarization. With OSPF, there'll actually be an additional interface made at The purpose of summarization, and this catches a lot of CCNP candidates without warning. Allow’s Have a look at the null0 interface And the way it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, and afterwards summarized.
interface Loopback16
ip tackle sixteen.sixteen.16.16 255.0.0.0
interface Loopback17
ip tackle 17.seventeen.17.17 255.0.0.0
interface Loopback18
ip address 18.18.eighteen.18 255.0.0.0
interface Loopback19
ip handle 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute connected subnets
R1(config-router)#summary-deal with 16.0.0.0 252.0.0.0
The summary address seems on R2, a downstream router.
R2#demonstrate ip route ospf
O E2 sixteen.0.0.0/6 [a hundred and ten/twenty] by means of 172.twelve.123.one, 00:00:05, Serial0
Allow’s return to R1 and take a look at its OSPF table.
R1#demonstrate ip route ospf
O sixteen.0.0.0/six is really a summary, 00:01:fifty one, Null0
The place did the null0 interface originate from, and why could it be there? Packets despatched for the null interface are dropped, and 먹튀 In such cases, that’s a superb factor.
Once you configure summary routes in OSPF, a route to null0 might be installed into the OSPF routing table. This helps to avoid routing loops. Any packets destined for that routes that have been summarized will likely have a longer match within the routing desk, as proven beneath…
C 17.0.0.0/eight is straight connected, Loopback17
C sixteen.0.0.0/8 is right related, Loopback16
C 19.0.0.0/8 is immediately related, Loopback19
C eighteen.0.0.0/eight is instantly connected, Loopback18
O 16.0.0.0/6 is actually a summary, 00:01:51, Null0
.. and packets that do not match among the list of summarized routes but do match the summary route is going to be dropped.
Stopping routing loops when executing route redistribution and summarization is vital. OSPF presents us a little bit help in that regard in this situation, and when you review additional complex redistribution scenarios with your strategy to the CCNP and CCIE, you’ll recognize that we’ll just take all the assistance we could get!