Symbolics XL LAN Challenges

I recently set up a LAN of my three XL Symbolics machines at home. The XL1201 which was having stability issues has been largely stabilized (thanks to help from David Schmidt). I will post more about this LAN soon, but I thought I would mention an interesting problem.

The machines connect to the LAN via an AUI to 10BaseT transceiver, to my core LAN which is a mixed 10G/1G LAN. The core router is a Ubiquiti EdgeRouter Pro which is attached to UNMS, their central management tool. When I connected these machines to the LAN, I was getting Merlin (the name of the CPU board) Ethernet errors on occasion, and eventually the computer would crash. I put the Symbolics computers on a separate segment connected only to a small Netgear switch and the EdgeRouter, but the computers kept crashing.

Eventually I ran a Wireshark on there, and noticed every 5 minutes or so a huge ARP request flood, asking every IP address 8 to 12 times for its MAC. I finally diagnosed this as part of the UNMS discovery protocol to find devices on the network. Once I added my new Symbolics segment to its "do not discover" blacklist, the network has become stable again. I guess feeding 8,000 ARPs into an ancient Ethernet communications chip is not good for stability.

More to come.

Screenshot with Ethernet Error

Douglas Fields

Writing LISP and Haskell since 1990