Tech

CCNP/ BSCI Examination Tutorial: Path Summarization And The OSPF Null Interface

CCNP examination success, especially on the BSCI test, needs you comprehend the details of path summarization. This ability not only requires that you have a convenience level with binary conversions, however you have to understand how and where to use path summarization with each private protocol.

You likewise need to know the “adverse effects” of path summarization. With OSPF, there will really be an extra user interface produced at the point of summarization, and this catches a lot of CCNP candidates by surprise. Let’s take a look at the null0 interface and how it associates with OSPF summarization.

On R1, the following networks are redistributed into OSPF, and after that summed up.

interface Loopback16

ip address 16.16.16.16 255.0.0.0

interface Loopback17

ip address 17.17.17.17 255.0.0.0

interface Loopback18

ip address 18.18.18.18 255.0.0.0

user interface Loopback19

ip address 19.19.19.19 255.0.0.0

R1( config) #router ospf 1

R1( config-router) #redistribute linked subnets

R1( config-router) #summary- address 16.0.0.0 252.0.0.0

The summary address appears on R2, a downstream router.

R2 #show ip route ospf

O E2 16.0.0.0/ 6 [110/20] through 172.12.123.1, 00:00:05, Serial0

Let’s return to R1 and take a look at its OSPF table.

R1 #show ip path ospf

O 16.0.0.0/ 6 is a summary, 00:01:51, Null0

Where did the null0 user interface originated from, and why is it there? Packages sent out to the null interface are dropped, and in this case, that’s a good idea.

A path to null0 will be set up into the OSPF routing table when you set up summary routes in OSPF. This assists to prevent routing loops. Any packets destined for the routes that have been summarized will have a longer match in the routing table, as revealed listed below …

C 17.0.0.0/ 8 is directly linked, Loopback17

C 16.0.0.0/ 8 is directly connected, Loopback16

C 19.0.0.0/ 8 is straight connected, Loopback19

C 18.0.0.0/ 8 is directly linked, Loopback18

O 16.0.0.0/ 6 is a summary, 00:01:51, Null0

. and packets that do not match one of the summarized routes but do match the summary route will be dropped.

When performing route redistribution and summarization is important, preventing routing loops. OSPF provides us a little help in that regard in this situation, and as you study more complex redistribution scenarios on your way to the CCNP and CCIE, you’ll realize that we’ll take all the assistance we can get!

You also have to know the “side effects” of path summarization. With OSPF, there will really be an additional interface developed at the point of summarization, and this catches a lot of CCNP prospects by surprise. When you configure summary paths in OSPF, a route to null0 will be set up into the OSPF routing table. This assists to avoid routing loops. Any packages destined for the paths that have been summarized will have a longer match in the routing table, as revealed below …

Also you have to be good on Linux and Linux Support

C 17.0.0.0/ 8 is directly connectedStraight Loopback17

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Check Also
Close
Back to top button