[c-nsp] OSPF Cost vs Injected Default Route

[Oliver Boehmer (oboehmer)]

> Let say 3 routers A, B and C running OSPF.
> A is ASBR, connected to B and C
> C connected to A directly & via B.
> 
> For router C which connected with two links :
>     - Primary (w/ default route injected from A)
>     - Secondary (w/ static default route + metric >110 to B)
> 
> In case of bad quality of primary link (not fully disconnected), I
> set cost 5000 on interface router A towards C.
> The default route changed to secondary.
> 
> How cost can affect the changing of default route ?

Not sure I grasp the full picture, but if you change the ospf cost on
the link from A to C (and only on A's side), the SPF on C should not
change at all (as his cost to A is still the same), so I'm a bit
puzzled.
Your static default route on C (with an admin distance of >110) should
only become active if there is no OSPF default route anymore, and this
should not happen if you just change the cost of a link.
Can you check the FA of the default route (see also
http://www.cisco.com/en/US/partner/tech/tk365/technologies_tech_note0918
6a008009405a.shtml#t3)..

	oli