Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

OSPF Type 4 LSA

Is it possible for an ASBR to originate a T4 or

T4 Indication LSA ?

3 REPLIES
Gold

Re: OSPF Type 4 LSA

If it's also the ABR, it will originate a type 4 into area 0. If it's an ABR on an NSSA area doing the type 7 to type 5 translation, it will also originate the type 4 into area 0. Type 4's are always generated by an ABR which is receiving a type 5 or type 7 from within it's area, so that the external metrics can be calculated correctly by routers outside the area receiving the type 5 LSA.

So, in any case, type 4's are always generated by ABR's, rather than ASBR, but a router could play both roles.

Russ.W

Re: OSPF Type 4 LSA

As far as I know Type 4 LSAs are originated ny ABRs. What is your purpose or case?

New Member

Re: OSPF Type 4 LSA

Given the following topology:

RIP (netA) ----ASBR----area 2-----ABR----area 0

Within area2 and 0 there will be a type 5 with a next hop of the ASBR router. Within area 2 this next hop is recursed through the type 1 and type 2 LSAs. Within area 0 the ASBRs advertisement in type1s and 2s can't be used, since they are area scope only. Therefore any type 1 ASBR LSA is converted to a type 4 LSA,

Regards

Ian

212
Views
0
Helpful
3
Replies