CCNP / BSCI Examination Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP exam achievements, notably about the BSCI exam, requires you have an understanding of the small print of route summarization. This skill don't just necessitates that you've got a convenience level with binary conversions, but you have to know the way and where to use route summarization with Every single personal protocol.
You even have to be aware of the “Uncomfortable side effects” of route summarization. With OSPF, there will truly be an additional interface created at The purpose of summarization, and this catches plenty of CCNP candidates without warning. Enable’s Look into the null0 interface And exactly how it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, after which summarized.
interface Loopback16
ip address 16.16.sixteen.sixteen 255.0.0.0
interface Loopback17
ip deal with 17.seventeen.seventeen.17 255.0.0.0
interface Loopback18
ip handle 18.18.eighteen.18 255.0.0.0
interface Loopback19
ip deal with 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 tackle appears on R2, a downstream router.
R2#demonstrate ip route ospf
O E2 sixteen.0.0.0/six [110/twenty] via 172.12.123.one, 00:00:05, Serial0
Permit’s go back to R1 and examine its OSPF table.
R1#show ip route ospf
O 16.0.0.0/6 is often a summary, 00:01:51, Null0
In which did the null0 interface come from, and why is it there? Packets despatched for the null interface are dropped, and in this case, that’s a fantastic factor.
After you configure 먹튀 summary routes in OSPF, a route to null0 will likely be set up into the OSPF routing desk. This will help to circumvent routing loops. Any packets destined with the routes that were summarized can have an extended match from the routing desk, as proven down below…
C seventeen.0.0.0/8 is right related, Loopback17
C sixteen.0.0.0/eight is straight related, Loopback16
C 19.0.0.0/eight is specifically related, Loopback19
C eighteen.0.0.0/eight is immediately connected, Loopback18
O 16.0.0.0/6 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 might be dropped.
Protecting against routing loops when undertaking route redistribution and summarization is significant. OSPF offers us a bit help in that regard in this situation, and as you study extra complex redistribution scenarios on your way to the CCNP and CCIE, you’ll recognize that we’ll choose all the assistance we could get!