I have a 877 IOS Router running 12.4 and a PIX 501 running 6.3(5).
I have configured a tunnel between the two firewalls and all protocols and ports seem to work okay apart from ICMP through the tunnel.
The config is designed so that the 877 router tunnels all traffic back to our hq so that we can filter internet etc..
I have tried inspecting icmp on the ios side and fixup icmp error on the pix side.
Any help would me much appreciated.