IP Routing Features

Configuring IP Parameters for Routing Switches

Enabling Proxy ARP

Proxy ARP allows a routing switch to answer ARP requests from devices on one network on behalf of devices in another network. Since ARP requests are MAC-layer broadcasts, they reach only the devices that are directly connected to the sender of the ARP request. Thus, ARP requests do not cross routers.

For example, if Proxy ARP is enabled on a routing switch connected to two sub-nets, 10.10.10.0/24 and 20.20.20.0/24, the routing switch can respond to an ARP request from 10.10.10.69 for the MAC address of the device with IP address 20.20.20.69. In standard ARP, a request from a device in the 10.10.10.0/ 24 sub-net cannot reach a device in the 20.20.20.0 sub-net if the sub-nets are on different network cables, and thus is not answered.

An ARP request from one sub-net can reach another sub-net when both sub- nets are on the same physical segment (Ethernet cable), since MAC-layer broadcasts reach all the devices on the segment.

Proxy ARP is disabled by default on HP routing switches. To enable Proxy ARP, enter the following commands from the VLAN context level in the CLI:

HPswitch(config)# vlan 1

HPswitch(vlan-1)# ip proxy-arp

To again disable IP proxy ARP, enter the following command:

HPswitch(vlan-1)# no ip proxy-arp

Syntax: [no] ip proxy-arp

Configuring Forwarding Parameters

The following configurable parameters control the forwarding behavior of HP routing switches:

Time-To-Live (TTL) threshold

Forwarding of directed broadcasts

All these parameters are global and thus affect all IP interfaces configured on the routing switch.

To configure these parameters, use the procedures in the following sections.

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