Network Setup

Here is the setup

3550 Port 1 (configured as router port) <-> port 1 3500 #1(configured as switch port access vlan 10) <-trunk-> 3500 #2 <-trunk-> 3500 #3 port 1(configured as switchport access vlan 10) <-> port 3/1 on 6503 (configured as router port)

3550 Port 1 has IP 10.0.0.21
6503 Port 3/1 has IP 10.0.0.22

the problem is the 6503 can ping the port on 3550(10.0.0.21) but the 3550 cannot ping 10.0.0.22

if i plug in a laptop to 3500 #3 port 1, everything works perfectly. so the trunk is working fine.

I tried connect laptop directly to the 6503 Port3/1 and able to ping both way.