This section describes the 7450 ESS or 7750 SR acting as a Broadband Subscriber Aggregator (BSA) with Layer 3 forwarding toward the network.
Local proxy ARP allows the 7450 ESS or 7750 SR to respond to ARP requests received on an interface, for an IP address which is part of a subnet assigned to the interface. When the local proxy ARP feature is enabled, the switch responds to all ARP requests for IP addresses belonging to the subnet with the MAC address of the interface, and forwards all traffic between hosts in the subnet.
This feature is intended to be used in situations (such as DSL aggregation networks) when hosts belonging to the same subnet are prevented from directly communicating with each other over the subnet by the configuration of the switch (or DSLAM) to which they are connected.
When local-proxy-arp is enabled under a IES service, all ICMP redirects on the ports associated with the service are automatically blocked. This prevents users from learning each other's MAC address (from ICMP redirects).
The implementation of proxy ARP with support for local proxy ARP allows the router to respond to ARP requests in the subnet assigned to an IES or VPRN interface, therefore allowing multiple customers to share the same IP subnet.