CCNP / BSCI Examination Tutorial: Route Summarization As well as OSPF Null Interface
CCNP exam results, significantly within the BSCI Examination, calls for you fully grasp the details of route summarization. This ability not just needs that you've a consolation stage with binary conversions, but You will need to understand how and wherever to apply route summarization with Every single specific protocol.
You even have to find out the “Unwanted side effects” of route summarization. With OSPF, there will in fact be an additional interface produced 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 relates to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, and then summarized.
interface Loopback16
ip handle sixteen.16.sixteen.16 255.0.0.0
interface Loopback17
ip address 17.seventeen.seventeen.17 255.0.0.0
interface Loopback18
ip handle 18.eighteen.eighteen.eighteen 먹튀검증 255.0.0.0
interface Loopback19
ip tackle 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute connected subnets
R1(config-router)#summary-tackle 16.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#demonstrate ip route ospf
O E2 sixteen.0.0.0/six [a hundred and ten/twenty] by using 172.twelve.123.one, 00:00:05, Serial0
Let’s go back to R1 and check out its OSPF table.
R1#clearly show ip route ospf
O 16.0.0.0/6 can be a summary, 00:01:51, Null0
In which did the null0 interface originate from, and why can it be there? Packets despatched for the null interface are dropped, and In this instance, that’s a fantastic issue.
Any time you configure summary routes in OSPF, a path to null0 will be put in to the OSPF routing desk. This aids to forestall routing loops. Any packets destined for the routes which have been summarized will likely have a longer match from the routing table, as proven down below…
C seventeen.0.0.0/8 is specifically linked, Loopback17
C 16.0.0.0/8 is straight connected, Loopback16
C 19.0.0.0/8 is directly connected, Loopback19
C 18.0.0.0/eight is instantly connected, Loopback18
O 16.0.0.0/six is a summary, 00:01:fifty one, Null0
.. and packets that do not match one of several summarized routes but do match the summary route will probably be dropped.
Protecting against routing loops when executing route redistribution and summarization is vital. OSPF presents us slightly help in that regard in this example, and while you research more sophisticated redistribution scenarios on the method to the CCNP and CCIE, you’ll understand that we’ll consider all the help we might get!