BNC-NETWORK-LAST TWO COMPUTERS IN ERROR

[pc81]

hi there i m from bosnia
now i m working on network for one school.
they have 13 computers and i have connected first five in bnc network.
when i connect 4 computers it works ok(i use 3com isa cards).
but when i add one more computer then 5 th computer see all computers exept computer no. 4.
and computer no. 4 dont see computer five.
they see each other but they cant enter to each other(ping does not work).
first 3 computers can enter in all computers and 4 th and 5 th can enter into them but
cant enter into each other.i check cables terminators and all and its ok.
but when i add one more computer (now 6 computers in network) then last 3 computers cant enter to each other and
can enter into firs 3 computers and first 3 can enter into them.
i have changed computers,cards.
i think that is something about ohms in cables or because of not (good) grounded eletrical instalations.
on network with 5 computers when i have 26 ohms in cable i have error with that last 2 computers but
when i have 18 ohms in network i have error with 3 last computers.i know that in network must be 25 ohms.
i have terminators at the end (50 ohms) and cabel(50 ohms) i have trying with grounded terminator but...
please help me if you can

 

[grygst76]

there are limitations to the amount of cable you use in any network also what type of network is it token ring? are you using a router or hub?

 

[edfair]

You probably have some NIC incompatibilities. And make sure you are using 58AU with a full shield. Limit of 100m end to end.
Had a working 10b2 with 9 nodes, added a 10th in the middle with about 5 additonal feet of coax and lost 2 nodes until I replaced every 58U link in the place.
Search on the web for ethernet cable and you will find a good description of what you need.
And lots of companies are packaging the wrong coax as ethernet and selling it. Most of the time it works, but it is a ticking time bomb.
And the cable mya not be marked 58au, it may be 802.3 as that is the spec.
And consider buying in bulk and making your own. Just be careful of the connectors. Buy from a reputable supplier. Ed Fair
efair@atlnet.com

Any advice I give is my best judgement based on my interpretation of the facts you supply.

Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.