CCNP / BSCI Exam Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP exam accomplishment, particularly over the BSCI Examination, demands you recognize the main points of route summarization. This talent not only necessitates that you've a comfort and ease stage with binary conversions, but You must know the way and in which to use route summarization with Just about every personal protocol.
You even have to know the “side effects” of route summarization. With OSPF, there will in fact be an extra interface developed at the point of summarization, and this catches lots of CCNP candidates by surprise. Allow’s Check out the null0 interface And just how it pertains to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, and then summarized.
interface Loopback16
ip handle sixteen.sixteen.16.sixteen 255.0.0.0
interface Loopback17
ip address seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip address eighteen.18.eighteen.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-address sixteen.0.0.0 252.0.0.0
The summary handle appears on R2, a downstream router.
R2#display ip route ospf
O E2 sixteen.0.0.0/6 [one hundred ten/twenty] by using 172.twelve.123.one, 00:00:05, Serial0
Let’s return to R1 토토 and check out its OSPF desk.
R1#demonstrate ip route ospf
O 16.0.0.0/six is actually a summary, 00:01:51, Null0
Where by did the null0 interface come from, and why could it be there? Packets sent on the null interface are dropped, and In this instance, that’s a great matter.
If you configure summary routes in OSPF, a route to null0 will probably be set up into your OSPF routing desk. This assists to prevent routing loops. Any packets destined for your routes which have been summarized should have an extended match in the routing desk, as revealed down below…
C 17.0.0.0/8 is right connected, Loopback17
C sixteen.0.0.0/8 is immediately related, Loopback16
C 19.0.0.0/8 is immediately connected, Loopback19
C 18.0.0.0/8 is immediately linked, Loopback18
O 16.0.0.0/6 is usually a summary, 00:01:51, Null0
.. and packets that do not match among the summarized routes but do match the summary route is going to be dropped.
Avoiding routing loops when undertaking route redistribution and summarization is important. OSPF offers us a bit assist in that regard in this situation, and while you research much more intricate redistribution eventualities on your own way to the CCNP and CCIE, you’ll recognize that we’ll consider all the help we may get!