OSPF Type 4 LSA

[kswonnell]

Is it possible for an ASBR to originate a T4 or

T4 Indication LSA ?

[ruwhite]

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

[kkalaycioglu]

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

[ipotts]

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