@ Aki,

Thanks... lemme try the trace on the switch -- however, since the first router [juniper] can reach the redback router through this same switch with the same vlan tagging... [see network diagram, all traffic btwn routers and firewall must go through switch]

we are suspecting the problem is not the switch but between Juniper firewall and Redback router. There could be an incompatibility in the tagging/encapsulation btn these two.