Hello,
I am not sure what you are trying to achieve. If you are just working on the
routing part, it will certainly work as long as you bypass the NAT on the
firewall (I am assuming that the Router A and Router B are on two different
interfaces of the ASA). Since you are using pre-8.3 code, you can configure
"no nat-control" and the ASA will not impose any NAT requirements.
As far as your first question about Lifesize, I think it does support NAT.
In Lifesize, there is an option to enable/disable NAT support. You need to
disable NAT aware feature (feature that tells Lifesize device to use public
IP when going to internet). Then you configure static NAT on the firewall
along with H.323/SIP inspects. That will make sure that your traffic goes to
internet without any issues.
Hope this helps.
Regards,
NT