IP routers and end nodes use ARP to determine the physical address of a node to which they want to send a packet. ARP is enabled by default. For one node to send a packet to another, the sending node must know the physical address of the destination node. The sending node, knowing only the destination IP address, first checks its ARP table for an entry that maps the destination IP address to the destination physical address. If the sending node finds the entry, it inserts the physical address into the packet and sends it. If the sending node does not find the entry in its ARP table, it broadcasts an ARP address request to the network. The destination node replies to the request with its own physical address, which the sending node uses to send the packet and adds to its ARP table for future use.
An IP router uses Proxy ARP when devices attached to one of its interfaces do not support IP subnetting and are unaware that they must go through the router to reach devices on other subnets of the same IP network. A router using Proxy ARP replies to ARP requests intended for devices on other subnets, but does so only if the device is reachable through the router. To determine whether the device is reachable, the router examines its own routing table.
Proxy ARP is required on the parent network of a stub subnet. The parent network has an IP address range that includes the IP address range of the stub subnet. The router responds to ARP requests sent on the parent network on behalf of devices on the stub subnet.
When both the parent and stub subnet are bound to IP interfaces, the router can detect the parent/stub subnet and automatically enable Proxy ARP for the appropriate interfaces. Even if Proxy ARP is not required, and not automatically enabled, you can still force it to be enabled with the Force Proxy ARP parameter.
You must enable Force Proxy ARP on each LAN interface on which the router must reply to ARP requests for destinations it can reach.
Force Proxy ARP is disabled on each interface by default. For more information, refer to Novell Internet Access Server 4.1 Routing Concepts.
To disable ARP on a LAN network interface, complete the following steps:
Load NIASCFG, then select the following parameter path:
Select Configure NIAS > Protocols and Routing > Bindings > an existing binding > Expert TCP/IP Bind Options
Select Use of ARP, then select Disabled.
Press Esc until you are prompted to save your changes, then select Yes.
Press Esc to return to the Internetworking Configuration menu.
If you want these changes to take effect immediately, select Reinitialize System and select Yes to activate your changes.
To enable Proxy ARP on a network interface, complete the following steps:
Load NIASCFG, then select the following parameter path:
Select Configure NIAS > Protocols and Routing > Bindings > an existing binding > Expert TCP/IP Bind Options
Select Force Proxy ARP, then select Enabled.
Press Esc until you are prompted to save your changes, then select Yes.
Press Esc to return to the Internetworking Configuration menu.
If you want these changes to take effect immediately, select Reinitialize System and select Yes to activate your changes.