3Com 10014299 manual

Map between WAN Interface IP Address and Link Layer Protocol Address 325

cannot receive the arp message, then possibly the error is on the Ethernet physical layer.

Fault 2: When the interface is encapsulated with PPP or Frame Relay, the link layer protocol status does not change to UP.

Troubleshooting: check whether the IP address of this interface is in the same network segment as the opposite side.

Fault 3: After the interface borrows an IP address, the link layer protocol status will turn to UP, but it can not ping through itself, and other ports can not ping through this borrowed IP address either.

Troubleshooting: Check whether the lender port is UP. Only when the port protocol of the lender is UP, will the address be added to the route table and pinged through by other ports.

Map between WAN Interface IP Address and Link Layer Protocol Address

In a router, you shall maintain both the mapping from an Ethernet interface IP address to an MAC address, and that from a WAN interface IP address to a link layer protocol address. Namely there are the following types:

■On a dialup interface (such as an asynchronous serial port or ISDN interface), mapping between IP address and dialing serial port is maintained by the command dialer route ip.

■On an interface encapsulated with X.25, the mapping between an IP address and X.121 address is maintained by the command x25 map ip.

■On an interface encapsulated with Frame Relay, mapping between an IP address and a virtual circuit number (DLCI) is maintained by the command fr map ip.

The above mapping tables are also called second routing tables, which are essential for the normal working of the router. For details, refer to related chapters in Link Layer Protocol.