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Can you set static IP addresses on them, If they are relying on DHCP then they won't be assigned an address from anything but a router and even that might fail sometimes.
according to the manual, the ips are 192.168.0.11 , 12 , 13, etc by default if network settings are set to no
but ive looked at the ip addy of customers router and assigned fixed addresses in the same range
ive tried pre built and self made cables - all checked with a network cable tester - and again - it works at random - perhaps once in 50 attempts!
as its now working on a wing and a prayer, and i can't make myself look any more of a numpty than i already have in front of the customer, im gonna have to "wing it" on this occasion and wait for the call to come in!!!
its not like i havent done this kind of thing over and over again over the past 35 years!! usually works first time. Sam4 comms has been pretty solid up til now - this install reminds me of the old uniwell daisy chained rs485 days 
