CCNP / BSCI Examination Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP exam achievements, specially to the BSCI exam, calls for you recognize the details of route summarization. This skill not just involves that you have a comfort and ease stage with binary conversions, but You will need to know the way and exactly where to apply route summarization with Every unique protocol.
You even have to understand the “Unwanted side effects” of route summarization. With OSPF, there will actually be an additional interface designed at The purpose of summarization, which catches loads of CCNP candidates unexpectedly. Let’s Examine the null0 interface And the way it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, after which summarized.
interface Loopback16
ip 먹튀검증 handle sixteen.16.16.16 255.0.0.0
interface Loopback17
ip tackle seventeen.17.17.seventeen 255.0.0.0
interface Loopback18
ip handle eighteen.eighteen.18.eighteen 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 related subnets
R1(config-router)#summary-handle sixteen.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#exhibit ip route ospf
O E2 16.0.0.0/six [110/20] by using 172.twelve.123.1, 00:00:05, Serial0
Let’s return to R1 and take a look at its OSPF table.
R1#present ip route ospf
O 16.0.0.0/six can be a summary, 00:01:51, Null0
The place did the null0 interface originate from, and why can it be there? Packets despatched into the null interface are dropped, and In such cases, that’s a good point.
Once you configure summary routes in OSPF, a route to null0 will be installed to the OSPF routing desk. This can help to circumvent routing loops. Any packets destined for the routes which have been summarized may have an extended match in the routing table, as revealed underneath…
C seventeen.0.0.0/8 is directly linked, Loopback17
C 16.0.0.0/eight is specifically connected, Loopback16
C 19.0.0.0/8 is right linked, Loopback19
C 18.0.0.0/eight is instantly related, Loopback18
O 16.0.0.0/6 is usually 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.
Avoiding routing loops when undertaking route redistribution and summarization is important. OSPF provides us just a little assist in that regard in this case, and when you research much more advanced redistribution scenarios on the approach to the CCNP and CCIE, you’ll recognize that we’ll just take all the help we might get!