Proxy Arp - ZyXEL Communications ZyWall ATP series User Manual

Table 91 Configuration > Network > Interface > Ethernet > Edit (continued)
LABEL
Add
Related Setting
Configure
PPPoE/PPTP
Configure VLAN
Configure WAN
TRUNK
Configure Policy
Route
OK
Cancel

9.3.2 Proxy ARP

An Address Resolution Protocol (ARP) is a protocol for mapping an IP address to a MAC address. An ARP
broadcast is sent to all devices in the same Ethernet network to request the MAC address of a target IP
address.
In the following figure, a host in a WAN subnet (A) broadcasts an ARP request to all devices within its
network in order to find the MAC address of a target IP address (172.16.x.x). However, the target IP
address may be in another subnet (B) that has the same network IP address (172.16.x.x). A router, such
as the Zyxel Device, does not forward broadcasts, so the request will not reach its destination.
Enable Proxy ARP (RFC 1027) to allow the Zyxel Device to answer external interface ARP requests on
behalf of a device on its internal interface. Interfaces supported are:
• Ethernet
• VLAN
• Bridge
The Zyxel Device sends its external MAC address to the WAN sender as the destination for the target IP
address. From then on the sender will send packets containing that target IP address directly to the
external interface of the Zyxel Device. The Zyxel Device then forwards the packet to the correct target IP
address in its LAN.
Chapter 9 Interfaces
DESCRIPTION
Click Add to create an IPv4 Address, an IPv4 CIDR (for example, 192.168.1.1/24) or an IPv4
Range (for example, 192.168.1.2-192.168.1.100) as the target IP address. The Zyxel Device
answers external ARP requests only if they match one of these inputted target IP addresses.
For example, if the IPv4 Address is 192.168.1.5, then the Zyxel Device will answer ARP
requests coming from the WAN only if it contains 192.168.1.5 as the target IP address.
Select an existing entry and click Remove to delete that entry.
Click PPPoE/PPTP if this interface's Internet connection uses PPPoE or PPTP or L2TP.
Click VLAN if you want to configure a VLAN interface for this Ethernet interface.
Click WAN TRUNK to go to a screen where you can set this interface to be part of a WAN
trunk for load balancing.
Click Policy Route to go to the policy route summary screen where you can manually
associate traffic with this interface.
You must manually configure a policy route to add routing and SNAT settings for an
interface with the Interface Type set to general. You can also configure a policy route to
override the default routing and SNAT behavior for an interface with an Interface Type of
internal or external.
Click OK to save your changes back to the Zyxel Device.
Click Cancel to exit this screen without saving.
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