In order to work, apple-talk uses both a node number and a network
number.  It also uses a network range. It is necessary that the network
number be within the network range. For example, on our CSLab MAC the
network range is: 10256-10511. The network number is 10351. A
cursory glance shows that the network number falls within the network
range. This is good. The network range is provided by netatalkd, the
Unix apple-talk daemon. The network number is self-configuring.

For some reason, 's network number did not fall within the network
range. This meant that he was not able to see the apple-talk network.

 and I tried various experiments to get the apple-talk client to
self-configure a suitable network number. This included rebooting the
MAC, stopping and starting apple-talk on the client, etc. Nothing helped.

Finally, we decided to try and assign the MAC an appropriate network number
that we had chosen, rather than allow it to find its own. This solved
the problem!

Steps

Apple Icon -> Control Panels -> AppleTalk -> Edit -> UserMode -> Administration

(This pops up a window that displays the network, node, and network range numbers)

Select "User defined" and manually set the network number. (We set it to: 10500)

Did not change the node number:61

Note:

To determine the network range: 

jane.cs:less /etc/atalkd.conf

# le0 -router -phase 2 -net 10256-10511 -addr 10256.141 -zone "CSLab"

Also:

jane.cs:/pkgs/netatalk-asun2.1.4-p29/bin/nbplkup

will provide a list of apple-talk clients on our network. Here is hectormac.ai's listing:

 hectormac.ai:AFPServer                          10500.61:254
 hectormac.ai:  Power Macintosh                  10500.61:251
 hectormac.ai:Workstation                        10500.61:4