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Strange problem with Ethernet switch

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  • Ethernet Switch
  • Routers
  • Switch
  • Networking
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Anonymous
September 7, 2004 1:57:43 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Hi,

I've been wondering for awhile about a problem that I'm having with an
Ethernet switch, so I hope that someone here can offer an explanation.

The switch is a Gigafast EE500-S. It's a 5-port 10/100 switch.

In my network, I have a Netgear router with a 4-port 10/100 switch,
built-in to the router, that connects to my cablemodem provider. I have
a cable going from one of the ports on the Netgear to the wall in one of
the rooms in my house.

If I plug a cable directly from the wall to the uplink port of the
Gigafast switch, I can ping my router and external destinations from any
PC that's connected directly to the Gigafast, but I get about 50%
timeouts.

If I ping any other computers directly connected to the Gigafast from
another computer on the Gigafast, everything is ok.

This is regardless of how I configure the NICs on the PCs connected to
the Gigafast (10 HDX or FDX, 100 HDX or FDX).


I kind of puzzled over this for awhile, but then, instead of connecting
the Gigafast uplink directly to the wall, I tried connecting an old
10Base-T hub between the Gigafast and the wall (i.e., Gigafast uplink
port to hub port via crossover cable, and then hub port to the wall),
and lo and behold, when I ping from any PCs connected to the Gigafast to
either my router or external destinations, no more timeouts.


I would love to eliminate the need for this "in-between" hub, but I
can't figure out why it's needed to get from the Gigafast to the router.


Can anyone here explain this?? Also, is there any way to allow me to
connect directly from the Gigafast to the wall, to the router?


Thanks,
Jim

More about : strange problem ethernet switch

Anonymous
September 7, 2004 2:47:01 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

ohaya wrote:

> Hi,
>
> I've been wondering for awhile about a problem that I'm having with an
> Ethernet switch, so I hope that someone here can offer an explanation.
>
> The switch is a Gigafast EE500-S. It's a 5-port 10/100 switch.
>
> In my network, I have a Netgear router with a 4-port 10/100 switch,
> built-in to the router, that connects to my cablemodem provider. I have
> a cable going from one of the ports on the Netgear to the wall in one of
> the rooms in my house.
>
> If I plug a cable directly from the wall to the uplink port of the
> Gigafast switch, I can ping my router and external destinations from any
> PC that's connected directly to the Gigafast, but I get about 50%
> timeouts.
>
> If I ping any other computers directly connected to the Gigafast from
> another computer on the Gigafast, everything is ok.
>
> This is regardless of how I configure the NICs on the PCs connected to
> the Gigafast (10 HDX or FDX, 100 HDX or FDX).
>
>
> I kind of puzzled over this for awhile, but then, instead of connecting
> the Gigafast uplink directly to the wall, I tried connecting an old
> 10Base-T hub between the Gigafast and the wall (i.e., Gigafast uplink
> port to hub port via crossover cable, and then hub port to the wall),
> and lo and behold, when I ping from any PCs connected to the Gigafast to
> either my router or external destinations, no more timeouts.
>
>
> I would love to eliminate the need for this "in-between" hub, but I
> can't figure out why it's needed to get from the Gigafast to the router.
>
>
> Can anyone here explain this?? Also, is there any way to allow me to
> connect directly from the Gigafast to the wall, to the router?

Sounds like a duplex mismatch between the Gigafast and the Netgear. Try
shutting _everything_ down then connecting the two, then power them up,
then power up the rest of your system. If that doesn't work, it could be a
bad cable that will carry 10 Mb/sec but not 100. Try running a known-good
cable directly between the two and see if the problem recurs. If so, then
before I wasted any more time troubleshooting it I'd replace the
Gigafast switch with a Netgear and see if it was an incompatibility.
>
>
> Thanks,
> Jim

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
September 7, 2004 10:57:16 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

rom the Gigafast to the wall, to the router?
>
> Sounds like a duplex mismatch between the Gigafast and the Netgear. Try
> shutting _everything_ down then connecting the two, then power them up,
> then power up the rest of your system. If that doesn't work, it could be a
> bad cable that will carry 10 Mb/sec but not 100. Try running a known-good
> cable directly between the two and see if the problem recurs. If so, then
> before I wasted any more time troubleshooting it I'd replace the
> Gigafast switch with a Netgear and see if it was an incompatibility.


John,

Thanks. I'll give that (powering the router and switch up first by
themselves), but it is the cable not being able to carry 100 Mbps,
shouldn't the switches (both the one inside the Netgear and the
standalone) be able to negotiate that? Both of these switches are
*suppose* to be "10/100" switches...

Jim
Related resources
Anonymous
September 8, 2004 12:03:17 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

ohaya wrote:

> rom the Gigafast to the wall, to the router?
>>
>> Sounds like a duplex mismatch between the Gigafast and the Netgear. Try
>> shutting _everything_ down then connecting the two, then power them up,
>> then power up the rest of your system. If that doesn't work, it could be
>> a
>> bad cable that will carry 10 Mb/sec but not 100. Try running a
>> known-good
>> cable directly between the two and see if the problem recurs. If so,
>> then before I wasted any more time troubleshooting it I'd replace the
>> Gigafast switch with a Netgear and see if it was an incompatibility.
>
>
> John,
>
> Thanks. I'll give that (powering the router and switch up first by
> themselves), but it is the cable not being able to carry 100 Mbps,
> shouldn't the switches (both the one inside the Netgear and the
> standalone) be able to negotiate that?

The quick answer is no. Fast Ethernet devices communicate with each other
at 10 Mb/sec to negotiate the capabilities of the devices at each end of
the cable and then switch to the highest performance level that both
support. All the negotiation though occurs at 10 Mb/sec. They do no
testing of the cable, and they have no fallback modes. If both devices
support 100 full duplex then that is what they set themselves for and if
the cable isn't up to it then communication is impaired in one manner or
another and to a greater or lesser degree depending on what's wrong with
the cable.

> Both of these switches are
> *suppose* to be "10/100" switches...
>
> Jim

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
September 8, 2004 6:02:33 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

ohaya wrote:

> Thanks. I'll give that (powering the router and switch up first by
> themselves), but it is the cable not being able to carry 100 Mbps,
> shouldn't the switches (both the one inside the Netgear and the
> standalone) be able to negotiate that? Both of these switches are
> *suppose* to be "10/100" switches...

No. Autonegotiation does not check for cable quality. It just checks
what the capabilities of the other end are, and will negotiate the best
combination. Whether the cable can actually support that is something
else entirely.

I agree with the previous poster that a duplex mismatch is the most
likely problem, with a split pair somewhere in the path a close second.

Regards,

Marco.
Anonymous
September 8, 2004 6:02:34 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"M.C. van den Bovenkamp" wrote:
>
> ohaya wrote:
>
> > Thanks. I'll give that (powering the router and switch up first by
> > themselves), but it is the cable not being able to carry 100 Mbps,
> > shouldn't the switches (both the one inside the Netgear and the
> > standalone) be able to negotiate that? Both of these switches are
> > *suppose* to be "10/100" switches...
>
> No. Autonegotiation does not check for cable quality. It just checks
> what the capabilities of the other end are, and will negotiate the best
> combination. Whether the cable can actually support that is something
> else entirely.
>
> I agree with the previous poster that a duplex mismatch is the most
> likely problem, with a split pair somewhere in the path a close second.
>


Marco,

Thanks for the clarification. Unfortunately, the cable is "in the
wall", so I can't do much about it. I tried the powering off/on, but
still the same results. I might to see if I can find a different switch
that might work.

I know that the Gigafast switch is unmanaged, but is there any
possibility that the port on the router might be configurable, i.e., so
I could try to force it to say, half-duplex?

FYI, I just noticed when I plug the cable from the wall directly into
the Gigafast switch, the FDX and 100 lights are lit solid, and the
LNK/ACT light is constantly blinking fast. According to the manual I
found, this is suppose to mean that there's data activity.

Jim
Anonymous
September 8, 2004 6:02:35 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

ohaya wrote:

>
>
> "M.C. van den Bovenkamp" wrote:
>>
>> ohaya wrote:
>>
>> > Thanks. I'll give that (powering the router and switch up first by
>> > themselves), but it is the cable not being able to carry 100 Mbps,
>> > shouldn't the switches (both the one inside the Netgear and the
>> > standalone) be able to negotiate that? Both of these switches are
>> > *suppose* to be "10/100" switches...
>>
>> No. Autonegotiation does not check for cable quality. It just checks
>> what the capabilities of the other end are, and will negotiate the best
>> combination. Whether the cable can actually support that is something
>> else entirely.
>>
>> I agree with the previous poster that a duplex mismatch is the most
>> likely problem, with a split pair somewhere in the path a close second.
>>
>
>
> Marco,
>
> Thanks for the clarification. Unfortunately, the cable is "in the
> wall", so I can't do much about it. I tried the powering off/on, but
> still the same results. I might to see if I can find a different switch
> that might work.
>
> I know that the Gigafast switch is unmanaged, but is there any
> possibility that the port on the router might be configurable, i.e., so
> I could try to force it to say, half-duplex?

Not on a Netgear. Netgear makes some Layer 3 managed switches for a
thousand bucks or so but they don't make any 4 port routers with management
on the switch ports.

You could spend 60 bucks for a couple of SMC 9452TX network adapters or
another built on the Marvell Yukon chipset and run the cable test software
they provide on the suspect cable--it uses the signal processors on the
gigabit chip to do many of the tests that a cable scanner would do. If you
find out for sure that the cable's bad you'll have a better idea what
you're up against. Or if you're in the Hartford/Springfield area and have
beer send me an email and I'll bring my Fluke over.

> FYI, I just noticed when I plug the cable from the wall directly into
> the Gigafast switch, the FDX and 100 lights are lit solid, and the
> LNK/ACT light is constantly blinking fast. According to the manual I
> found, this is suppose to mean that there's data activity.
>
> Jim

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
September 8, 2004 7:01:11 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

ohaya wrote:

> I know that the Gigafast switch is unmanaged, but is there any
> possibility that the port on the router might be configurable, i.e., so
> I could try to force it to say, half-duplex?

Depends. If it is possible, the docs of your Netgear should mention it.

Do the Netgear and the Gigafast have LEDs to indicate duplex? If so, you
could see whether they agree on things.

If they do agree on duplex mode (either half or full), a botched cable
is the most likely problem, and if you can't fix it, running the link at
10Mbps is the only option. Split pairs will do that to you (link that
works fine at 10, but doesn't work or works badly at 100).

> FYI, I just noticed when I plug the cable from the wall directly into
> the Gigafast switch, the FDX and 100 lights are lit solid, and the
> LNK/ACT light is constantly blinking fast. According to the manual I
> found, this is suppose to mean that there's data activity.

So the Gigafast has LEDs. Does the Netgear, and do they agree on duplex
mode? Speed is OK, or the link wouldn't work at all.

Regards,

Marco.
Anonymous
September 8, 2004 8:40:53 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

ohaya <ohaya@cox.net> wrote:
> themselves), but it is the cable not being able to carry 100 Mbps,
> shouldn't the switches (both the one inside the Netgear and the
> standalone) be able to negotiate that? Both of these switches are
> *suppose* to be "10/100" switches...

If you have a split pair, the switch may think the cable
can do 100, but it can only in one direction. The autoneg
works on _advertised_ capabilities, not measured.

-- Robert
Anonymous
September 8, 2004 8:44:57 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

ohaya <ohaya@cox.net> wrote:
> Thanks for the clarification. Unfortunately, the cable is
> "in the wall", so I can't do much about it.

Actually, so long as the cable is good quality Cat5 not
overpulled or kinked, split pairs can be fixed.

> FYI, I just noticed when I plug the cable from the wall
> directly into the Gigafast switch,

"Cable from the wall directly" ... do you mean there
isn't a jack & patchcord? Somebody crimped a plug on
cable in the wall? A very likely cause of split pairs.

-- Robert
Anonymous
September 8, 2004 8:44:58 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Robert Redelmeier wrote:
>
> ohaya <ohaya@cox.net> wrote:
> > Thanks for the clarification. Unfortunately, the cable is
> > "in the wall", so I can't do much about it.
>
> Actually, so long as the cable is good quality Cat5 not
> overpulled or kinked, split pairs can be fixed.
>
> > FYI, I just noticed when I plug the cable from the wall
> > directly into the Gigafast switch,
>
> "Cable from the wall directly" ... do you mean there
> isn't a jack & patchcord? Somebody crimped a plug on
> cable in the wall? A very likely cause of split pairs.
>
> -- Robert


Robert,

I worded that unclearly. Yes, there's a wallplate, and I have a
male-male patch cable connecting from the wall to Gigafast switch (or
the hub).

So the config that works:

This cable is "in the wall"
|
V
Router <======//====> Wall <=======> Hub <======> Switch <========> PCs
(Bsmt) Plate

And the config that I'm having problems with:

Router <======//=====> Wall <========> Switch <========> PCs
(Bsmt) Plate


Sorry if I was imprecise.
Jim
Anonymous
September 8, 2004 5:25:49 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

ohaya <ohaya@cox.net> wrote:
> I worded that unclearly. Yes, there's a wallplate, and I have a
> male-male patch cable connecting from the wall to Gigafast switch
> (or the hub).
>
> So the config that works:
>
> This cable is "in the wall"
> |
> V
> Router <======//====> Wall <=======> Hub <======> Switch <========> PCs
> (Bsmt) Plate
>
> And the config that I'm having problems with:
>
> Router <======//=====> Wall <========> Switch <========> PCs
> (Bsmt) Plate


Much clearer! Maybe the router and/or switch expects a crossover
cable or an "uplink" port to be used. The hub does the XOVER.
Try a replacing the patch-cable with a crossover cable.

Either that or the router or cable won't do 100 MHz correctly.
The cable in the basement at the router end, it is also a
factory patch-cord?

-- Robert
Anonymous
September 8, 2004 8:14:59 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Robert Redelmeier wrote:

> Much clearer! Maybe the router and/or switch expects a crossover
> cable or an "uplink" port to be used. The hub does the XOVER.
> Try a replacing the patch-cable with a crossover cable.

No, that can't be it. In that case the link wouldn't even come up, and
that's not his problem.

> Either that or the router or cable won't do 100 MHz correctly.
> The cable in the basement at the router end, it is also a
> factory patch-cord?

What I haven't yet seen an answer to, do router and switch agree on
duplex mode? A duplex mismatch is still a possibility. That, or a
miswired cable.

Regards,

Marco.
Anonymous
September 9, 2004 1:17:32 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"M.C. van den Bovenkamp" wrote:
>
> Robert Redelmeier wrote:
>
> > Much clearer! Maybe the router and/or switch expects a crossover
> > cable or an "uplink" port to be used. The hub does the XOVER.
> > Try a replacing the patch-cable with a crossover cable.
>
> No, that can't be it. In that case the link wouldn't even come up, and
> that's not his problem.
>
> > Either that or the router or cable won't do 100 MHz correctly.
> > The cable in the basement at the router end, it is also a
> > factory patch-cord?
>
> What I haven't yet seen an answer to, do router and switch agree on
> duplex mode? A duplex mismatch is still a possibility. That, or a
> miswired cable.


M.C.,

Sorry, I might've missed that question.

Yes, both router and switch have FDX and 100 lights lit solid. The
LNK/ACT light on the switch is fast blinking (too fast, like it's noise)
when I try this.

Jim
Anonymous
September 9, 2004 1:20:41 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Robert Redelmeier wrote:
>
> ohaya <ohaya@cox.net> wrote:
> > I worded that unclearly. Yes, there's a wallplate, and I have a
> > male-male patch cable connecting from the wall to Gigafast switch
> > (or the hub).
> >
> > So the config that works:
> >
> > This cable is "in the wall"
> > |
> > V
> > Router <======//====> Wall <=======> Hub <======> Switch <========> PCs
> > (Bsmt) Plate
> >
> > And the config that I'm having problems with:
> >
> > Router <======//=====> Wall <========> Switch <========> PCs
> > (Bsmt) Plate
>
> Much clearer! Maybe the router and/or switch expects a crossover
> cable or an "uplink" port to be used. The hub does the XOVER.
> Try a replacing the patch-cable with a crossover cable.
>
> Either that or the router or cable won't do 100 MHz correctly.
> The cable in the basement at the router end, it is also a
> factory patch-cord?

Robert,

The switch has two connectors for port 1, a "normal" and an "uplink"
connector. If I plug the cable from the wall into the "normal"
connector on the switch, I get no lights. If I plug the calbe into the
"uplink" connector on the switch, I get FDX and 100 lights solid, and
fast blinking LNK/ACT light.

I have a new switch (an SMC 16-port 10/100) on its way, and I'll give
that a try when it gets in. If that doesn't work, I guess I'm stuck
with the hub+switch configuration (seems like such a waste of the hub
though).

Jim
Anonymous
September 9, 2004 6:11:29 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

ohaya <ohaya@cox.net> wrote:
> The switch has two connectors for port 1, a "normal" and an
> "uplink" connector. If I plug the cable from the wall into the
> "normal" connector on the switch, I get no lights.

Yes, as pointed out by another poster, a crossover mis-match
would result in not working at all.

> If I plug the calbe into the "uplink" connector on the switch,
> I get FDX and 100 lights solid, and fast blinking LNK/ACT light.

This could well be a split pair (data errors). Are there _any_
home-made crimped plugs in the cabling?

-- Robert
February 1, 2005 12:15:25 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Try another switch, its possible that switch is damaged.

I had a customer's switch take a dump after a bad lightening storm. Same
problem...it worked, but bad packet loss.

"ohaya" <ohaya@cox.net> wrote in message news:413DBE57.F6164229@cox.net...
> Hi,
>
> I've been wondering for awhile about a problem that I'm having with an
> Ethernet switch, so I hope that someone here can offer an explanation.
>
> The switch is a Gigafast EE500-S. It's a 5-port 10/100 switch.
>
> In my network, I have a Netgear router with a 4-port 10/100 switch,
> built-in to the router, that connects to my cablemodem provider. I have
> a cable going from one of the ports on the Netgear to the wall in one of
> the rooms in my house.
>
> If I plug a cable directly from the wall to the uplink port of the
> Gigafast switch, I can ping my router and external destinations from any
> PC that's connected directly to the Gigafast, but I get about 50%
> timeouts.
>
> If I ping any other computers directly connected to the Gigafast from
> another computer on the Gigafast, everything is ok.
>
> This is regardless of how I configure the NICs on the PCs connected to
> the Gigafast (10 HDX or FDX, 100 HDX or FDX).
>
>
> I kind of puzzled over this for awhile, but then, instead of connecting
> the Gigafast uplink directly to the wall, I tried connecting an old
> 10Base-T hub between the Gigafast and the wall (i.e., Gigafast uplink
> port to hub port via crossover cable, and then hub port to the wall),
> and lo and behold, when I ping from any PCs connected to the Gigafast to
> either my router or external destinations, no more timeouts.
>
>
> I would love to eliminate the need for this "in-between" hub, but I
> can't figure out why it's needed to get from the Gigafast to the router.
>
>
> Can anyone here explain this?? Also, is there any way to allow me to
> connect directly from the Gigafast to the wall, to the router?
>
>
> Thanks,
> Jim
!