SonicOS 7 System

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Technical Documentation > SonicOS 7 System > Interfaces > Interface Settings IPv4 > Layer 2 Bridged Mode > Comparing L2 Bridged Mode to Transparent Mode > ARP in Transparent Mode

ARP in Transparent Mode

ARP (Address Resolution Protocol: the mechanism by which unique hardware addresses on network interface cards are associated to IP addresses) is proxied in Transparent Mode. If the Workstation on Server on the left had previously resolved the Router (192.168.0.1) to its MAC address 00:99:10:10:10:10, this cached ARP entry would have to be cleared before these hosts could communicate through the appliance. This is because the appliance proxies (or answers on behalf of) the gateway’s IP (192.168.0.1) for hosts connected to interfaces operating in Transparent Mode. So when the Workstation at the left attempts to resolve 192.168.0.1, the ARP request it sends is responded to by the appliance with its own X0 MAC address (00:06:B1:10:10:10).

The appliance also proxy ARPs the IP addresses specified in the Transparent Range (192.168.0.100 to 192.168.0.250) assigned to an interface in Transparent Mode for ARP requests received on the X1 (Primary WAN) interface. If the router had previously resolved the server (192.168.0.100) to its MAC address 00:AA:BB:CC:DD:EE, this cached ARP entry would have to be cleared before the router could communicate with the host through the appliance. This typically requires a flushing of the router’s ARP cache either from its management interface or through a reboot. When the router’s ARP cache is cleared, the router can then send a new ARP request for 192.168.0.100, to which the appliance responds with its X1 MAC 00:06:B1:10:10:11.

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