Network technologies and trends

Jan 27 2016   6:00AM GMT

How to configure OSPF Totally Stubby Area in Cisco Routers- Series 2?

Yasir Irfan Yasir Irfan Profile: Yasir Irfan

Tags:
Cisco
Cisco IOS
Cisco Routers
IP Routing
Loopback
OSPF
OSPF protocol
Routing
Routing Table

In my previous post we studied the topology and saw how Type 3, Type 4 and Type  LSA routes are installed in non 0 Area. Now lets configure Area 5 as a Totally Stubby Area and see what impact it will have

In order to configure Totally Stubby Area one should use the following Cisco IOS Command in an ABR under OSPF process

router ospf 1

area x stub no-summary

And on the non ABR router of Totally Stubby Area as the following Cisco IOS commands

router ospf 1

area x stub

In our case we need to configure Area 5 as Totally stubby area by using the below Cisco IOS command in Routers R2  which happens to be ABR

R2 OSPF Totally Stubby

And in R3 Router

R3 Totally Stub

Now we have successfully configured Area 5 as Totally Stubby Area, we could see R2 is learning R4 loopback networks 10.0.1.0, 10.0.2.0, 10.0.3.0 & 10.0.4.0 as Type 5 LSA ( OPPF external type 2 routes) and R1-R4 link networks 192.168.14.0 as Type 3 LSA ( Inter area routes) and R2 will inject remove these routes and inject them with a  default route to R3.

R2 -R4 routers

R3 can now only see a default route and if we check the OSPF Data base there are no more Inter-Area specific routes,

R3 Totally Stubby

R3 OSPF Data base TS

Also we cannot see the R4 loopback interface 10.0.1.0 network in the routing table , how ever its there in CEF table

R3 Cef table

And we ping the loopback 1 interface IP 10.0.1.1 of R4

R3 -R4 ping

Well Totally Stubby Area is great feature which helps in reducing the OSPF Database size and also it reduces the CPU utilization of a router.

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