Alcatel-Lucent 7750 SR-OS, Configuration Manual

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Configuring IP Router Parameters
Page 40 7750 SR OS Router Configuration Guide
Proxy ARP
Proxy ARP is the technique in which a router answers ARP requests intended for another node.
The router appears to be present on the same network as the “real” node that is the target of the
ARP and takes responsibility for routing packets to the “real” destination. Proxy ARP can help
nodes on a subnet reach remote subnets without configuring routing or a default gateway.
Typical routers only support proxy ARP for directly attached networks; the router is targeted to
support proxy ARP for all known networks in the routing instance where the virtual interface
proxy ARP is configured.
In order to support DSLAM and other edge like environments, proxy ARP supports policies that
allow the provider to configure prefix lists that determine for which target networks proxy ARP
will be attempted and prefix lists that determine for which source hosts proxy ARP will be
attempted.
In addition, the proxy ARP implementation will support the ability to respond for other hosts
within the local subnet domain. This is needed in environments such as DSL where multiple hosts
are in the same subnet but can not reach each other directly.
Static ARP is used when an Alcatel-Lucent router needs to know about a device on an interface
that cannot or does not respond to ARP requests. Thus, the configuration can state that if it has a
packet with a certain IP address to send it to the corresponding ARP address. Use proxy ARP so
the router responds to ARP requests on behalf of another device.