said by ynyng:The problem is that the SonicWall as firewall device expect to see only ARP broadcast for only /28 network. When the SonicWall sees ARP broadcast intended for different network, by nature the SonicWall firewall drops the broadcast.
I have Cisco 3825 with an Ether interface using a secondary IP address to isloate a /28 subnet out of a /24:
ip address xxx.yyy.zzz.33 255.255.255.240 secondary
ip address xxx.yyy.zzz.1 255.255.255.0
The downstream router on the /28 network (a SonicWall) uses xxx.yyy.zzz.34/28 as its address and xxx.yyy.zzz.33 as its trusted gateway. The problem is that the Ciso interface sends out ARP broadcasts for both the /24 and the /28 networks and the SonicWall is configured to drop packets when it sees ARP traffic from the /24 network.