General Configuration Using Local ManagementCSX400 and CSX400-DC User’s Guide 1593. Use the arrow keys to highlight the SAVE command field at the bottom of the screen and thenpress ENTER. The message “SAVED OK” displays.The entry for the UDP Port option reflects the UDP port number that is currently selected. Theentry for UDP Type names the UDP service to which that port number corresponds.Enabling Proxy ARP on a PortBy default, Proxy Address Resolution Protocol (ARP) is disabled on all ports, and IP RoutingServices respond only to ARP requests addressed to its own IP address.For one IP host to communicate with another IP host, knowledge of the target host’s MAC addressmust be known. To learn this MAC address, the IP host sends an ARP request packet as a LANbroadcast with the destination IP address of the target IP host. All hosts receive this broadcast andthe one host that matches the target IP address responds with its MAC-layer address. However,because each subnet constitutes a separate broadcast domain and LAN broadcasts are notforwarded across routers, ARP does not work beyond a host’s local network or subnetwork. One ofthe primary purposes of a router is to confine LAN broadcast traffic to each local network orsubnetwork.A proxy ARP response is generated when the following occurs:• Proxy ARP is enabled on a router port.• An ARP request is received as a LAN broadcast (looking for the MAC-layer address of an IPhost on another network segment).• An entry exists in the IP Forwarding Table for the destination host’s network.Enabling Proxy ARP on a router port allows IP hosts to dynamically obtain the MAC-layer addressof other IP hosts attached to different networks or subnetworks by using broadcast ARP requestpackets. With Proxy ARP enabled, IP hosts are not required to maintain knowledge of specificsubnetworks.To enable Proxy ARP on a router port, complete the following steps:1. Use the arrow keys to highlight the Proxy ARP option.2. Use the ENTER key to toggle the entry to ENABLED.NOTEYou can type in the UDP port number, or you can use the +REDIRECTOR- option atthe bottom of the screen to scroll through a list of commonly used UDP port numbers.To use the +REDIRECTOR- option, use the arrow keys to highlight the + (to goforward), or the - (to go backward), and then press the ENTER key to scroll in thedirection that you selected.
