CCNP / BSCI Exam Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP exam achievement, specially to the BSCI Test, needs you fully grasp the details of route summarization. This ability not just necessitates that you've a consolation degree with binary conversions, but You must know how and exactly where to use route summarization with Every individual protocol.
You even have to know the “Unintended effects” of route summarization. With OSPF, there will actually be an additional interface made at the point of summarization, and this catches loads of CCNP candidates by surprise. Permit’s Examine the null0 interface and how it pertains to OSPF summarization.
On R1, the following networks are redistributed into OSPF, and then summarized.
interface Loopback16
ip address sixteen.sixteen.sixteen.16 255.0.0.0
interface Loopback17
ip tackle 17.seventeen.seventeen.seventeen 255.0.0.0
interface 먹튀 Loopback18
ip tackle 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 connected subnets
R1(config-router)#summary-address 16.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#clearly show ip route ospf
O E2 sixteen.0.0.0/6 [a hundred and ten/twenty] via 172.12.123.one, 00:00:05, Serial0
Permit’s return to R1 and look at its OSPF desk.
R1#show ip route ospf
O 16.0.0.0/six is actually a summary, 00:01:51, Null0
In which did the null0 interface originate from, and why could it be there? Packets sent to the null interface are dropped, and In this instance, that’s a superb thing.
After you configure summary routes in OSPF, a route to null0 is going to be put in into the OSPF routing desk. This allows to forestall routing loops. Any packets destined to the routes which were summarized will have a longer match inside the routing table, as shown underneath…
C 17.0.0.0/8 is specifically related, Loopback17
C sixteen.0.0.0/eight is specifically linked, Loopback16
C 19.0.0.0/eight is specifically linked, Loopback19
C eighteen.0.0.0/8 is right related, Loopback18
O 16.0.0.0/six is often a summary, 00:01:fifty one, Null0
.. and packets that don't match one of several summarized routes but do match the summary route will probably be dropped.
Avoiding routing loops when performing route redistribution and summarization is vital. OSPF provides us somewhat assist in that regard in this case, and as you analyze a lot more intricate redistribution situations on the solution to the CCNP and CCIE, you’ll understand that we’ll choose all the assistance we can get!