CCNP / BSCI Test Tutorial: Route Summarization And also the OSPF Null Interface
CCNP Test success, especially on the BSCI exam, demands you understand the details of route summarization. This ability don't just calls for that you've a convenience degree with binary conversions, but You need to know how and in which to use route summarization with Just about every person protocol.
You also have to learn the “side effects” of route summarization. With OSPF, there'll basically be an extra interface developed at The purpose of summarization, and this catches a great deal of CCNP candidates unexpectedly. Permit’s Look into 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 deal with 16.16.sixteen.sixteen 255.0.0.0
interface Loopback17
ip address seventeen.17.17.17 255.0.0.0
interface Loopback18
ip handle 18.eighteen.eighteen.eighteen 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 connected subnets
R1(config-router)#summary-deal with 16.0.0.0 252.0.0.0
The summary deal with appears 토토사이트 on R2, a downstream router.
R2#show ip route ospf
O E2 sixteen.0.0.0/six [a hundred and ten/20] through 172.twelve.123.one, 00:00:05, Serial0
Permit’s go back to R1 and have a look at its OSPF desk.
R1#show ip route ospf
O sixteen.0.0.0/6 is actually a summary, 00:01:51, Null0
Where did the null0 interface come from, and why can it be there? Packets despatched to the null interface are dropped, and In cases like this, that’s a good issue.
After you configure summary routes in OSPF, a path to null0 will probably be installed in the OSPF routing desk. This will help to prevent routing loops. Any packets destined for your routes that have been summarized could have a longer match in the routing table, as shown below…
C seventeen.0.0.0/eight is right related, Loopback17
C 16.0.0.0/eight is directly connected, Loopback16
C 19.0.0.0/8 is specifically connected, Loopback19
C eighteen.0.0.0/eight is right connected, Loopback18
O 16.0.0.0/6 is really a summary, 00:01:51, Null0
.. and packets that don't match among the list of summarized routes but do match the summary route might be dropped.
Blocking routing loops when accomplishing route redistribution and summarization is vital. OSPF provides us slightly assist in that regard in this example, and as you study more complex redistribution situations on the approach to the CCNP and CCIE, you’ll know that we’ll get all the help we could get!