CCNP / BSCI Test Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP exam achievements, particularly on the BSCI Examination, calls for you comprehend the small print of route summarization. This talent not simply necessitates that you've a comfort stage with binary conversions, but You must understand how and in which to apply route summarization with Each and every specific protocol.
You even have to learn the “Unwanted effects” of route summarization. With OSPF, there will in fact be an additional interface designed at The purpose of summarization, and this catches a great deal of CCNP candidates by surprise. Enable’s take a look at the null0 interface And just how it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, and afterwards summarized.
interface Loopback16
ip handle 16.16.sixteen.16 255.0.0.0
interface Loopback17
ip handle 17.17.seventeen.seventeen 255.0.0.0
interface Loopback18
ip address eighteen.eighteen.eighteen.eighteen 255.0.0.0
interface Loopback19
ip tackle 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute related subnets
R1(config-router)#summary-handle 16.0.0.0 252.0.0.0
The summary handle seems on R2, a downstream router.
R2#demonstrate ip route ospf
O E2 sixteen.0.0.0/6 [a hundred and ten/20] through 172.12.123.1, 00:00:05, Serial0
Allow’s 먹튀 return to R1 and check out its OSPF desk.
R1#demonstrate ip route ospf
O sixteen.0.0.0/six is usually a summary, 00:01:fifty one, Null0
The place did the null0 interface come from, and why can it be there? Packets sent into the null interface are dropped, and In this instance, that’s a great detail.
If you configure summary routes in OSPF, a route to null0 will probably be put in into your OSPF routing desk. This helps to prevent routing loops. Any packets destined for your routes which were summarized could have a longer match in the routing desk, as proven beneath…
C 17.0.0.0/eight is immediately connected, Loopback17
C sixteen.0.0.0/8 is instantly linked, Loopback16
C 19.0.0.0/eight is directly connected, Loopback19
C eighteen.0.0.0/eight is immediately related, Loopback18
O sixteen.0.0.0/6 is a summary, 00:01:fifty one, Null0
.. and packets that do not match on the list of 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 help in that regard in this case, and while you examine extra complex redistribution eventualities on the approach to the CCNP and CCIE, you’ll know that we’ll take all the assistance we may get!