I have site-to-site VPN between HQ & branch-office
OSPF is the routing protocol used between VPN Tunnel.
Since I have limited bandwidth at branch-office ;
I need to restrict ospf update once a day
I need to know ; how to restrict the updates once a day
Giuseppe, you're welcome, although I regret being the one to reduce your "batting average" to only .999 ;)
"I was focusing on the fact that demand circuits can be useless if you keep the link in area 0 where it is exposed to every topology change. "
Perhaps, but even within area 0, you might design a very stable area 0 topology if you have just area summary addresses and externals injected by statics. I.e., it might not always be useless even within area 0. However, it does make more sense, to restrict the technique to stub areas.
Amin, stepping back just a little, the real purpose for this technique was to avoid repeatly bringing up a dial-up/on-demand link for just routing hellos and avoiding toll charges, not so much to save bandwidth across the link when it was available. As Giuseppe also noted in his first post, OSPF maintenance bandwidth usage is low.
Careful OSPF design and tuning OSPF parameters can further minimize OSPF's bandwidth utilization (along with speeding convergence and increasing stability).
For your purposes, the real bandwidth savings of this technique is avoidance of periodic OSPF hellos (which don't use much bandwidth) or the periodic LSA refresh (bandwidth?), but unless you look carefully at your overall design, you could still have a lot happening when there is OSPF topology activity.