IPv6 routing on AEBS

My G5 AEBS (MD031LL/A) running 7.6 now has an option under IPv6 to set the mode to router. This does not show up on my G1 (MA073LL/A) also running 7.6. Anyone know which generations of the AEBS support the IPv6 routing mode? Has any information been released about this feature being enabled at some point on the older units?

 

According to http://lists.apple.com/archives/Ipv6-dev/2009/Oct/msg00086.html IPv6 router mode was first found in the 4th generation units released in late-2009 and will not be back-ported to older models.