CCNP / BSCI Examination Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP Examination accomplishment, particularly over the BSCI Examination, requires you recognize the details of route summarization. This ability not merely involves you have a consolation stage with binary conversions, but You should know the way and where by to apply route summarization with Every particular person protocol.
You also have to be aware of the “Uncomfortable side effects” of route summarization. With OSPF, there'll really be an additional interface established at the point of summarization, and this catches plenty of CCNP candidates without warning. Allow’s Examine the null0 interface And just how it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, then summarized.
interface Loopback16
ip tackle 16.16.16.sixteen 255.0.0.0
interface Loopback17
ip deal with seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip address eighteen.eighteen.18.18 255.0.0.0
interface Loopback19
ip address 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-tackle sixteen.0.0.0 252.0.0.0
The summary deal with seems on R2, a downstream router.
R2#clearly show ip route ospf
O E2 16.0.0.0/six [a hundred and ten/20] via 172.twelve.123.1, 00:00:05, Serial0
Allow’s return to R1 and examine 토토 its OSPF table.
R1#display ip route ospf
O 16.0.0.0/six is actually a summary, 00:01:51, Null0
Exactly where did the null0 interface come from, and why is it there? Packets despatched into the null interface are dropped, and In such cases, that’s a good matter.
Once you configure summary routes in OSPF, a route to null0 will be installed in to the OSPF routing table. This can help to stop routing loops. Any packets destined for the routes which have been summarized may have an extended match within the routing table, as demonstrated below…
C 17.0.0.0/8 is right linked, Loopback17
C sixteen.0.0.0/eight is directly connected, Loopback16
C 19.0.0.0/8 is directly linked, Loopback19
C eighteen.0.0.0/8 is right connected, Loopback18
O 16.0.0.0/6 is a summary, 00:01:fifty one, Null0
.. and packets that don't match one of many summarized routes but do match the summary route will probably be dropped.
Preventing routing loops when carrying out route redistribution and summarization is important. OSPF presents us a bit assist in that regard in this case, and when you study extra intricate redistribution scenarios on the approach to the CCNP and CCIE, you’ll realize that we’ll just take all the help we could possibly get!