STUB / TOTALLY STUB

STUB

Stub area is created inorder to stop redistributed routes into an ospf area , that means type 5 lsa's are not allowed which are generated due to redistribution.Creating an area stub makes the abr generate default route which is pointing towards itself


The best way of presenting a topology with stub area is shown below

click on the image to view large




In this topology area 0 will have OE2 routes in the routing table. OE2 routes are the redistributed routes from eigrp autonomous system into ospf.

Since area 1 is stub area, so type 5 lsa are not allowed.so abr will inject default route pointing towards itself in R4 ( fig ).so only OIA* route will be seen along with the inter-area routes.

If lsa type 3 are to be blocked then typing the command on the abr will block lsa type 3 also and default route is injected pointed towards abr.



Configuration for creating stub area(based on the figure above)


R4


router4>
router4>en
router4#conf terminal
router4(config)#router ospf 1
router4(config-router)#area 1 stub


R5


router5>
router5>en
router5#conf terminal
router5(config)#router ospf 1
router5(config-router)#area 1 stub


Configuration for creating totally stub area(based on the figure above)


R4
router4>
router4>en
router4#conf terminal
router4(config)#router ospf 1
router4(config-router)#area 1 stub no-summary


R5

router5>
router5>en
router5#conf terminal
router5(config)#router ospf 1
router5(config-router)#area 1 stub no-summary