CCNP / BSCI Exam Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP Examination results, notably on the BSCI Examination, demands you understand the details of route summarization. This skill not just requires that you've got a ease and comfort 토토 level with binary conversions, but You must know how and wherever to apply route summarization with Every single particular person protocol.
You also have to find out the “Unwanted side effects” of route summarization. With OSPF, there will in fact be an extra interface developed at The purpose of summarization, which catches many CCNP candidates without warning. Allow’s Check out the null0 interface And the way it relates to OSPF summarization.
On R1, the next networks are redistributed into OSPF, and afterwards summarized.
interface Loopback16
ip handle sixteen.16.16.16 255.0.0.0
interface Loopback17
ip deal with 17.seventeen.seventeen.seventeen 255.0.0.0
interface Loopback18
ip handle 18.18.eighteen.eighteen 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 connected subnets
R1(config-router)#summary-handle 16.0.0.0 252.0.0.0
The summary address appears on R2, a downstream router.
R2#display ip route ospf
O E2 sixteen.0.0.0/6 [one hundred ten/20] by means of 172.twelve.123.1, 00:00:05, Serial0
Enable’s return to R1 and evaluate its OSPF desk.
R1#exhibit ip route ospf
O 16.0.0.0/6 can be a summary, 00:01:fifty one, Null0
Where did the null0 interface come from, and why can it be there? Packets despatched towards the null interface are dropped, and In cases like this, that’s a very good issue.
When you configure summary routes in OSPF, a route to null0 will probably be mounted into the OSPF routing table. This allows to forestall routing loops. Any packets destined to the routes which were summarized could have a longer match in the routing table, as proven below…
C 17.0.0.0/8 is directly connected, Loopback17
C sixteen.0.0.0/eight is directly connected, Loopback16
C 19.0.0.0/eight is immediately related, Loopback19
C 18.0.0.0/8 is specifically connected, 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 is going to be dropped.
Protecting against routing loops when executing route redistribution and summarization is vital. OSPF presents us a bit assist in that regard in this case, and while you analyze more advanced redistribution situations in your way to the CCNP and CCIE, you’ll recognize that we’ll acquire all the assistance we could get!