VPN Traffic Routing between multi-sites

Hi, All,

I have hub-and-spoke Fierwall network like the following:

SiteA ----(VPN) -------> SiteB < ----- (VPN)------ SiteC

SiteA is using PIX506E (V6.3) SiteB is using PIX515E (V6.3) SiteC is using PIX506E (V6.3)

Traffic from SiteA to SiteB is working fine; traffic from SiteC to SiteB is working fine.

What should I configure the SiteB in order to let traffic from SiteA to SiteC, and verse visa ? Do I have to upgrade the IOS of all PIX to V7.0 ?

Thank you very much.

Cheers :B