IBM SG24-4817-00 manual Association between IP and MAC Address

This soft copy for use by IBM employees only.

4.7.4 Association between IP and MAC Address

The ATM TR/Ethernet Bridge Module can be reached via four LAN ports and/or one ATM port, but it has only a single IP address that is assigned to it at the time of configuration. This IP address will be associated with the first port on the ATM TR/Ethernet Bridge Module that connects to a network successfully. If more than one port is configured for the ATM TR/Ethernet Bridge Module, there will be a race condition to determine which port is associated with the IP address.

The MAC address of the port associated with the IP address will be used in the response to the ARP requests sent to the IP address of the ATM TR/Ethernet Bridge Module, regardless of the port on which the ARP request is received. If the port which is associated with the IP address of the ATM TR/Ethernet Bridge Module becomes disabled (say the cable is disconnected), the IP-to-MAC address association will remain unchanged. This means that the ATM TR/Ethernet Bridge Module will still respond to ARP requests with the MAC address of the port that was initially associated with the IP address of the ATM TR/Ethernet Bridge Module. This ensures that the ARP table entry in the stations that communicate with the ATM TR/Ethernet Bridge Module via the IP will still be valid regardless of the fact that the port with that MAC address may be down.

If the ATM TR/Ethernet Bridge Module is reset and the MAC address of another port is associated with the IP address of the ATM TR/Ethernet Bridge Module, the ARP table entry in the stations that were communicating with the ATM TR/Ethernet Bridge Module will become invalid. Those stations will not be able to communicate with the ATM-LAN Bridge module via IP until their ARP table entry is aged-out or is deleted by the user to allow the IP station to discover the new MAC address associated with the ATM TR/Ethernet Bridge Module. Therefore, if you have problems communicating with the ATM TR/Ethernet Bridge Module via IP, one of the first things that you can do is to delete the ARP entry in your IP workstation to enable it to rediscover the ATM TR/Ethernet Bridge Module via the ARP process.

4.7.5 ATM TR/Ethernet Bridge Module Configuration Utility Program

The Configuration Utility Program is a DOS/Windows-based application that enables a user to modify the ATM TR/Ethernet Bridge Module′s configuration parameters, to change the operating code, and to use minimal mode. The following is the list of the functions that can be performed using the Configuration Utility Program:

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Create a bridge profile

Edit a bridge profile

View a bridge profile

Save a bridge profile to the hard disk

Delete a bridge profile from the hard disk

Send a bridge profile to the ATM TR/Ethernet Bridge Module

Retrieve current configuration parameters from an ATM-LAN Bridge Module

Load new operational parameters from an ATM-LAN Bridge Module

View vital product data (VPD) for an ATM TR/Ethernet Bridge Module

Erase the configuration for an ATM TR/Ethernet Bridge Module

62ATM Workgroup Solutions: Implementing the 8285 ATM Switch