CCNP / BSCI Exam Tutorial: Route Summarization And The OSPF Null Interface
CCNP Test achievements, notably about the BSCI exam, demands you comprehend the main points of route summarization. This skill don't just involves that you've got a comfort and ease amount with binary conversions, but You must understand how and where by to use route summarization with Each individual specific protocol.
You also have to understand the “Negative effects” of route summarization. With OSPF, there'll basically be an additional interface created at The purpose of summarization, and this catches a great deal of CCNP candidates abruptly. Permit’s Have a look at the null0 interface And exactly how it relates to OSPF summarization.
On R1, the next networks are redistributed into OSPF, after which you can summarized.
interface Loopback16
ip handle sixteen.16.16.sixteen 255.0.0.0
interface Loopback17
ip handle 17.17.17.seventeen 255.0.0.0
interface Loopback18
ip address eighteen.18.eighteen.18 255.0.0.0
interface Loopback19
ip address 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-deal with sixteen.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#present ip route ospf
O E2 sixteen.0.0.0/6 [110/twenty] by using 172.twelve.123.1, 00:00:05, Serial0
Enable’s 토토 go back to R1 and check out its OSPF desk.
R1#show ip route ospf
O 16.0.0.0/six is really a summary, 00:01:fifty one, Null0
In which did the null0 interface come from, and why can it be there? Packets despatched into the null interface are dropped, and In such a case, that’s a good point.
If you configure summary routes in OSPF, a path to null0 is going to be installed in to the OSPF routing table. This helps to stop routing loops. Any packets destined for the routes that have been summarized can have a longer match while in the routing table, as shown below…
C 17.0.0.0/eight is specifically connected, Loopback17
C 16.0.0.0/eight is directly linked, Loopback16
C 19.0.0.0/8 is directly connected, Loopback19
C 18.0.0.0/eight is straight linked, Loopback18
O 16.0.0.0/6 is usually a summary, 00:01:51, Null0
.. and packets that do not match one of many summarized routes but do match the summary route will probably be dropped.
Avoiding routing loops when executing route redistribution and summarization is important. OSPF provides us a little assist in that regard in this situation, and as you analyze much more sophisticated redistribution eventualities with your way to the CCNP and CCIE, you’ll realize that we’ll choose all the assistance we might get!