CCNP / BSCI Exam Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP exam achievements, especially over the BSCI Examination, needs you realize the details of route summarization. This talent not just involves that you have a comfort stage with binary conversions, but You need to know the way and where by to use route summarization with Each and every individual protocol.
You even have to learn the “side effects” of route summarization. With OSPF, there'll actually be an additional interface created at The purpose of summarization, which catches lots of CCNP candidates by surprise. Allow’s Examine the null0 interface And exactly how it relates to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, then summarized.
interface Loopback16
ip tackle sixteen.16.sixteen.16 255.0.0.0
interface Loopback17
ip tackle seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip address 18.eighteen.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 sixteen.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#clearly show ip route ospf
O E2 16.0.0.0/six [one hundred ten/twenty] by way of 172.twelve.123.1, 00:00:05, Serial0
Let’s go back to R1 and take a look at its OSPF table.
R1#present ip route ospf
O sixteen.0.0.0/6 is actually a summary, 00:01:51, Null0
Wherever did the null0 interface come from, and why can it be there? Packets despatched into the null interface are dropped, and in this case, that’s an excellent matter.
If you configure summary routes in OSPF, a route to null0 will probably be put in in the OSPF routing desk. This assists to prevent routing loops. Any packets destined with the 먹튀 routes that were summarized will have an extended match inside the routing table, as proven below…
C 17.0.0.0/8 is instantly related, Loopback17
C sixteen.0.0.0/8 is specifically related, Loopback16
C 19.0.0.0/eight is right connected, Loopback19
C 18.0.0.0/eight is directly related, Loopback18
O 16.0.0.0/6 is often a summary, 00:01:51, Null0
.. and packets that don't match among the summarized routes but do match the summary route might be dropped.
Avoiding routing loops when doing route redistribution and summarization is vital. OSPF gives us somewhat help in that regard in this situation, and while you study far more elaborate redistribution eventualities with your strategy to the CCNP and CCIE, you’ll realize that we’ll acquire all the help we could get!