electrical isolation, switches, ARP and ethernet over UTP

electrical isolation, switches, ARP and ethernet over UTP

Post by Max Metra » Thu, 05 Jun 2003 12:00:12



Ok, I'm going to try to make this as simple as possible so I'll save the
history unless it turns out to be useful.

I'm running UTP from one place, about 30 feet, into a Bay Networks 350T
switch.  The rest of the switch connects are Cat5.  I've also "tuned down"
this port to be 10bT Full Duplex as opposed to 100bT.  When I plug in this
device, ARP stops working.  Yes, that's right, ARP.  Everything else works
fine, just not ARP.  The only guess I have is that a broadcast somehow
electrically couples the whole switch?  So here's my questions, any help
appreciated:

1) I thought a switch was supposed to stop this kind of madness?  Doesn't it
provide full electrical isolation?

2) Is there something that DOES provide this isolation?  Something that
essentially reassembles ethernet frames and provides total electrical
independence?  Preferably some sort of mini adapter or converter?

3) Am I likely missing something more trivial here?

Thanks much for any help and sorry for the cross posting but I'm desparate.

 
 
 

electrical isolation, switches, ARP and ethernet over UTP

Post by Barry Parke » Thu, 05 Jun 2003 17:20:09


I'm not a Bay man but I have had problems with their defaults before.
A switch is supposed to send broadcasts to all ports.
(How else would a devices find another?)

 Is permit broadcasts set on the ports?

I have had a problem with Bay not passing multicasts unless set correctly
so I presume that broadcasts can be turned off as well.

Barry.


Quote:> Ok, I'm going to try to make this as simple as possible so I'll save the
> history unless it turns out to be useful.

> I'm running UTP from one place, about 30 feet, into a Bay Networks 350T
> switch.  The rest of the switch connects are Cat5.  I've also "tuned down"
> this port to be 10bT Full Duplex as opposed to 100bT.  When I plug in this
> device, ARP stops working.  Yes, that's right, ARP.  Everything else works
> fine, just not ARP.  The only guess I have is that a broadcast somehow
> electrically couples the whole switch?  So here's my questions, any help
> appreciated:

> 1) I thought a switch was supposed to stop this kind of madness?  Doesn't
it
> provide full electrical isolation?

> 2) Is there something that DOES provide this isolation?  Something that
> essentially reassembles ethernet frames and provides total electrical
> independence?  Preferably some sort of mini adapter or converter?

> 3) Am I likely missing something more trivial here?

> Thanks much for any help and sorry for the cross posting but I'm
desparate.


 
 
 

electrical isolation, switches, ARP and ethernet over UTP

Post by Max Metra » Thu, 05 Jun 2003 21:51:57


It could be misconfiged somehow, although I don't see how adding a unit
would make it break, and removing it would make it work again.

I agree that broadcast has to go to all ports, I just wonder if that means
that they are momentarily ELECTRICALLY coupled or if the switch
"retransmits" the broadcast packet on its own.

Strangely, I changed that port to 100/Half and it seems to be behaving
better.  This sure is confusing.


> I'm not a Bay man but I have had problems with their defaults before.
> A switch is supposed to send broadcasts to all ports.
> (How else would a devices find another?)

>  Is permit broadcasts set on the ports?

> I have had a problem with Bay not passing multicasts unless set correctly
> so I presume that broadcasts can be turned off as well.

> Barry.



> > Ok, I'm going to try to make this as simple as possible so I'll save the
> > history unless it turns out to be useful.

> > I'm running UTP from one place, about 30 feet, into a Bay Networks 350T
> > switch.  The rest of the switch connects are Cat5.  I've also "tuned
down"
> > this port to be 10bT Full Duplex as opposed to 100bT.  When I plug in
this
> > device, ARP stops working.  Yes, that's right, ARP.  Everything else
works
> > fine, just not ARP.  The only guess I have is that a broadcast somehow
> > electrically couples the whole switch?  So here's my questions, any help
> > appreciated:

> > 1) I thought a switch was supposed to stop this kind of madness?
Doesn't
> it
> > provide full electrical isolation?

> > 2) Is there something that DOES provide this isolation?  Something that
> > essentially reassembles ethernet frames and provides total electrical
> > independence?  Preferably some sort of mini adapter or converter?

> > 3) Am I likely missing something more trivial here?

> > Thanks much for any help and sorry for the cross posting but I'm
> desparate.

 
 
 

electrical isolation, switches, ARP and ethernet over UTP

Post by Bo » Fri, 06 Jun 2003 00:25:55


This might be totally unhelpful, but for what it's worth:
I had a problem with a linksys switch when one of the ports
connected to a half duplex hub.  Maybe when some of the
ports are half duplex and some of them are full duplex
the broadcast might not get to every port.
I would try disconnecting everything except the ARP requester
and ARP responder to see if that makes a difference.

Anyway, I'm not an IT person, so this may be silly advice.

Bob


> Ok, I'm going to try to make this as simple as possible so I'll save the
> history unless it turns out to be useful.

> I'm running UTP from one place, about 30 feet, into a Bay Networks 350T
> switch.  The rest of the switch connects are Cat5.  I've also "tuned down"
> this port to be 10bT Full Duplex as opposed to 100bT.  When I plug in this
> device, ARP stops working.  Yes, that's right, ARP.  Everything else works
> fine, just not ARP.  The only guess I have is that a broadcast somehow
> electrically couples the whole switch?  So here's my questions, any help
> appreciated:

> 1) I thought a switch was supposed to stop this kind of madness?  Doesn't it
> provide full electrical isolation?

> 2) Is there something that DOES provide this isolation?  Something that
> essentially reassembles ethernet frames and provides total electrical
> independence?  Preferably some sort of mini adapter or converter?

> 3) Am I likely missing something more trivial here?

> Thanks much for any help and sorry for the cross posting but I'm desparate.

 
 
 

1. electrical isolation, switches, ARP and ethernet over UTP

Ok, I'm going to try to make this as simple as possible so I'll save the
history unless it turns out to be useful.

I'm running UTP from one place, about 30 feet, into a Bay Networks 350T
switch.  The rest of the switch connects are Cat5.  I've also "tuned down"
this port to be 10bT Full Duplex as opposed to 100bT.  When I plug in this
device, ARP stops working.  Yes, that's right, ARP.  Everything else works
fine, just not ARP.  The only guess I have is that a broadcast somehow
electrically couples the whole switch?  So here's my questions, any help
appreciated:

1) I thought a switch was supposed to stop this kind of madness?  Doesn't it
provide full electrical isolation?

2) Is there something that DOES provide this isolation?  Something that
essentially reassembles ethernet frames and provides total electrical
independence?  Preferably some sort of mini adapter or converter?

3) Am I likely missing something more trivial here?

Thanks much for any help and sorry for the cross posting but I'm desparate.

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