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Configuring IP Router Parameters
Page 26 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 7750 SR-Series 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, 7750 SR-Series 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 7750 SR OS 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 a 7750 SR OS needs to know about a device on an interface that cannot or
does not respond to ARP requests. Thus, the 7750 SR OS configuration can state that if it has a
packet that has a certain IP address to send it to the corresponding ARP address. Use proxy ARP so
the 7750 SR responds to ARP requests on behalf of another device.