CCNP / BSCI Exam Tutorial: Route Summarization As well as the OSPF Null Interface
CCNP exam success, significantly on the BSCI Examination, requires you understand the details of route summarization. This ability not simply necessitates that you've got a convenience amount with binary conversions, but It's important to know how and where by to apply route summarization with Just about every personal protocol.
You even have to be aware of the “Unwanted side effects” of route summarization. With OSPF, there'll truly be an additional interface established at The purpose of summarization, and this catches many CCNP candidates without warning. Let’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, after which summarized.
interface Loopback16
ip handle 16.16.16.sixteen 255.0.0.0
interface Loopback17
ip tackle 17.17.seventeen.17 255.0.0.0
interface Loopback18
ip deal with eighteen.18.18.eighteen 255.0.0.0
interface Loopback19
ip handle 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute related subnets
R1(config-router)#summary-deal with sixteen.0.0.0 252.0.0.0
The summary handle seems on R2, a downstream router.
R2#present ip route ospf
O E2 16.0.0.0/6 [110/twenty] by using 172.twelve.123.1, 00:00:05, Serial0
Permit’s go back to R1 and look 토토사이트 at its OSPF desk.
R1#display ip route ospf
O 16.0.0.0/6 is a summary, 00:01:fifty one, Null0
Where did the null0 interface come from, and why can it be there? Packets despatched to your null interface are dropped, and In cases like this, that’s a fantastic thing.
Any time you configure summary routes in OSPF, a path to null0 will likely be mounted into the OSPF routing table. This helps to avoid routing loops. Any packets destined for the routes which were summarized may have a longer match during the routing desk, as shown beneath…
C seventeen.0.0.0/eight is directly related, Loopback17
C 16.0.0.0/eight is specifically linked, Loopback16
C 19.0.0.0/eight is directly connected, Loopback19
C eighteen.0.0.0/8 is directly linked, Loopback18
O sixteen.0.0.0/6 is usually a summary, 00:01:51, Null0
.. and packets that do not match among the summarized routes but do match the summary route will likely be dropped.
Avoiding routing loops when performing route redistribution and summarization is vital. OSPF offers us a bit help in that regard in this situation, and when you review much more complex redistribution situations on the method to the CCNP and CCIE, you’ll recognize that we’ll choose all the assistance we will get!