A strange problem occurred when setting up a route.

A strange problem occurred when setting up a route-Linux Enterprise Application-Linux server application information. For details, refer to the following section. I used three Red Hat Enterprise Linux 5 machines (A, B, C) to build A routing experiment.
There are two NICs on machine A used as the Routing Server. I run the following command)
# Ifconfig eth0 192.168.8.254 netmask 255.255.255.0
# Ifconfig eth1 192.168.9.254 netmask 255.255.255.0
# Route add-net 192.168.8.0 netmask 255.255.255.0 eth0
# Route add-net 192.168.9.0 netmask 255.255.255.0 eth1
# Echo 1/proc/sys/net/ipv4/ip_forward

The remaining two machines B and C each have an Nic. I run the following commands respectively: (I have only configured these network configurations for these two machines, and both are successful)
A:
# Ifconfig eth0 192.168.8.191 netmask 255.255.255.0
# Route add default gw 192.168.8.254 eth0
B:
# Ifconfig eth0 192.168.9.191 netmask 255.255.255.0
# Route add default gw 192.168.9.254 eth0

The current situation is as follows: (the iptables of A is the same as that of none)
A can ping B and C, and B and C can also ping two IP addresses of.
But B cannot ping C, and C cannot ping B.

Thank you !!!