Some Ethernet-ISDN bridges used for remote LAN-to-LAN connectivity drop the connection when there is no active data transfer, and dial on demand when there is information to be transferred. If a user's local network does not include an AppleTalk router, a message appears each time the connection is dropped.
There is also an issue with Apple Remote Access 3.0 which can cause the message. ARA processes incoming Router Table Maintenance Protocol (RTMP) packets. ARA 3.0 incorrectly processes these packets. On some networks, this can cause the client to assume that the network is inaccessible. In this situation, an alert is posted to notify the user that access to the AppleTalk network has been interrupted. If additional RTMP packets are processed correctly, the network is assumed to be available again. ARA Client 3.1.2, which ships with Mac OS 8.5, resolves this issue.
Workarounds include:
1. Disable Apple Remote Access 3.0 extensions via the Extensions manager control panel.
2. Use the "AppleTalk Options" control panel, available by downloading "OT 1.1.2-Extras.sea" from the Apple Software Updates site.
After downloading, the AppleTalk Options control panel is located in the Open Transport Extras -> Network Options -> AppleTalk folder.
- Drag the control panel to your System Folder and Restart.
- After restarting the computer, check the option for "Suppress router-related alerts."
Note: This option will only avoid the interruption message, it will not resolve any loss of network connectivity.
3. Select the Advanced User mode in the AppleTalk control panel (select User Mode under the Edit Menu). Once you are in Advanced User mode, check the User defined box. Enter a valid network number and try a random node number (between 1 and 253) and close the AppleTalk control panel. If the node number is not already being used you can reopen the control panel and uncheck the User defined box. If the node number is already being used, reopen the control panel and try another node number. Repeat the process until a valid AppleTalk address is entered.
If the problem still occurs after the above suggestions the next thing to do is to test the unit on an isolated network to see if it only occurs on the large network.
Article 24549 titled
ARA 3.0: "AppleTalk Network Not Available" Message, may be of some assistance in resolving this issue also.
This article can help you locate the software update mentioned here: