CCNP / BSCI Examination Tutorial: Route Summarization And The OSPF Null Interface
CCNP Examination accomplishment, notably within the BSCI Test, needs you realize the small print of route summarization. This ability not only demands that you've got a ease and comfort level with binary conversions, but You will need to know the way and exactly where to apply route summarization with each person protocol.
You even have to understand the “Uncomfortable side effects” of route summarization. With OSPF, there will basically be an extra interface created at the point of summarization, which catches many CCNP candidates unexpectedly. Allow’s Have a look at the null0 interface And exactly how it pertains to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, then summarized.
interface Loopback16
ip tackle 16.16.sixteen.sixteen 255.0.0.0
interface Loopback17
ip handle seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip address eighteen.18.18.18 255.0.0.0
interface Loopback19
ip tackle 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-address sixteen.0.0.0 252.0.0.0
The summary deal with appears on R2, a downstream router.
R2#demonstrate ip route ospf
O E2 16.0.0.0/6 [110/twenty] by means of 172.twelve.123.1, 00:00:05, Serial0
Allow’s go back to R1 and check out its OSPF table.
R1#demonstrate ip route ospf
O sixteen.0.0.0/six can be a summary, 00:01:51, Null0
The place did the null0 interface originate from, and why could it be there? Packets despatched for the null interface are dropped, and in this case, that’s a great thing.
Once you configure summary routes in OSPF, a route to null0 might be set up in the OSPF routing desk. This helps to stop routing loops. Any packets destined for your routes that were summarized may have a longer match inside the routing table, as shown below…
C seventeen.0.0.0/eight is right connected, Loopback17
C 16.0.0.0/eight is directly connected, Loopback16
C 19.0.0.0/8 is directly related, Loopback19
C eighteen.0.0.0/eight is right connected, Loopback18
O 16.0.0.0/six is a summary, 00:01:51, Null0
.. and packets that do not match on the list of summarized routes but do match the summary route are going to be dropped.
Blocking routing loops when undertaking route redistribution and summarization is significant. OSPF presents 먹튀검증 us just a little help in that regard in this case, and as you review a lot more advanced redistribution situations on the solution to the CCNP and CCIE, you’ll understand that we’ll consider all the assistance we could possibly get!