Fiber Backbone

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I posted a message last week on DHCP not working at one segment of the
network and have determined that its not the server but in how my fiber
backbone is laid out. I had the fibers check and they are in good working
condition. However, the length of the fibers are probably causing me the
problems with network errors. This is what I have as followed: A-350'-B
B-622'-C C-1100-D D-400-E. My servers are located in the D area. If I moved
the servers to the C area would this solve my length problem? Also at each
Letter, I have a 3com 100 switch with a fiber module.

thanks, steve
 
in message
:I posted a message last week on DHCP not working at one segment of the
: network and have determined that its not the server but in how my fiber
: backbone is laid out. I had the fibers check and they are in good working
: condition. However, the length of the fibers are probably causing me the
: problems with network errors. This is what I have as followed: A-350'-B
: B-622'-C C-1100-D D-400-E. My servers are located in the D area. If I
moved
: the servers to the C area would this solve my length problem? Also at
each
: Letter, I have a 3com 100 switch with a fiber module.

Steve...

You had the "fibers check"? What does that mean exactly?
I've never had anyone perform an OTDR test and report "good working
condition." I'm am being facetious but it means nothing on this end.
What tests were run?
What were the results? Please do not interpret.

If the length was the issue, the fiber would not have passed. There is a
length test, several actually.
62.5/125 micron dual-mode fiber supports distances of 2K.
I seriously doubt you're using single-mode.

The 3COM 100 switch is which model, housing which fiber module, at what
speed and at what duplex?
Please provide manufacturer's part number.

A 3COM: BR-549 with a Fiber Module: OICU812 is better than 3COM 100 with a
fiber module.
100BASE-LX, -SX, -FX, -FL?
FDDI?
Most likely IEEE 802.3u 100BASE-FX, running on 62.5/125 micron dual-mode
fiber, means you have a maximum distance of 2K.

You have 2472'.
A foot is 0.3048 meters.
2472 * 0.3048 = 753.4656 meters

It's probably not the distance. You can't daisy chain fiber so how do you
connect between the "areas", what equipment is involved, where are the
issues (which area) and what are the errors?

If it's not getting an IP address, then which OS and are you getting 0.0.0.0
or an APIPA address (169.254.x.x)?

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
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I'll second Roland's analysis - the fiber lengths are not your problem, you
need to work the problem through even though it may take some time to
definitively diagnose the actual problem.

--
Richard G. Harper [MVP Shell/User] (e-mail address removed)
* PLEASE post all messages and replies in the newsgroups
* for the benefit of all. Private mail is usually not replied to.
* My website, such as it is ... http://rgharper.mvps.org/
* HELP us help YOU ... http://www.dts-l.org/goodpost.htm
 
Steve said:
I posted a message last week on DHCP not working at one segment of the
network and have determined that its not the server but in how my fiber
backbone is laid out. I had the fibers check and they are in good working
condition. However, the length of the fibers are probably causing me the
problems with network errors. This is what I have as followed: A-350'-B
B-622'-C C-1100-D D-400-E. My servers are located in the D area. If I moved
the servers to the C area would this solve my length problem? Also at each
Letter, I have a 3com 100 switch with a fiber module.
Click to expand...

[What Roland and Richard said with these
thoughts added...]

You say that DHCP doesn't work (that is
pretty vague) but does that mean that if you
assigne static addresses that IP, pinging
and routing etc will work?

If so, a good first guess would be some
sort of blocking of the broadcasts (either
by passing a switch that is a ROUTER
or by traversing a BAD bridge or repeater
that isn't propagating the broadcasts as it
should.)

A simple (the free Server version) NetMon
or other sniffer type device can determine
if the server is 'seeing' the broadcasts and/or
trying to answer them.

If you have a more general problem than DHCP
it would be better to report the full symptoms
and the exact errors you experience.
 
Ok this is what I have found:

All switches 3COM 3300 24/port 3C16980
with 3C16971 100Base-FX dual module

All Fiber is 6 tube 62.5/125

All Patch cords 62.5/125

Reference designator:
[Letter] = Switch location
[jn#] = Junction fiber ends Numbered
pt = Patch cord

There are 3 segments

A-pt2'-[jn1]--350'--[jn2]-pt5'-B

B-pt5'-[jn2]-pt10'-[jn3]--500'--[jn4]--122'-[jn5]--1000'--[jn6]--100

'--[jn7]-pt10'-D

E-pt5'-[jn8]--400--[jn6]--100--[jn7]-pt10'-D

A,B, & C did go to the 3com switches via the fiber and those three
went into one switch that had the server connected in to. One of the network
segments would fail and I had to keep unpluging the fiber and reconnect to
get it working. 3COM said something about the buffers were overloaded.
But now I have another device that the 3 segments terminate into a

media convertor. 10/100Base-TX to 100Base-FX
KTI Networks, KC-300D-C

This stopped the network from going down but does not solve the DHCP
with Building1. I could put A on its own segment but not sure if
this will help. I plan on installing a server in each building to
serve as file and print sharing and backup AD to ease up on the
network stress. Bulding1 can run all of there programs, ERP,
Internet access, File shares off of D servers and so on. Its slow
but it works. Also I am running on a class B network but plan on
changing it to a class C.

Hope this gives you a better look at my layout.
and thanks for your help, its been the best ever. :)
 
in message
: Ok this is what I have found:
:
: All switches 3COM 3300 24/port 3C16980
: with 3C16971 100Base-FX dual module
:
: All Fiber is 6 tube 62.5/125
:
: All Patch cords 62.5/125
:
: Reference designator:
: [Letter] = Switch location
: [jn#] = Junction fiber ends Numbered
: pt = Patch cord
:
: There are 3 segments
:
: A-pt2'-[jn1]--350'--[jn2]-pt5'-B
:
: B-pt5'-[jn2]-pt10'-[jn3]--500'--[jn4]--122'-[jn5]--1000'--[jn6]--100
:
: '--[jn7]-pt10'-D
:
: E-pt5'-[jn8]--400--[jn6]--100--[jn7]-pt10'-D
:
: A,B, & C did go to the 3com switches via the fiber and those three
: went into one switch that had the server connected in to. One of the
network
: segments would fail and I had to keep unpluging the fiber and reconnect to
: get it working. 3COM said something about the buffers were overloaded.
: But now I have another device that the 3 segments terminate into a
:
: media convertor. 10/100Base-TX to 100Base-FX
: KTI Networks, KC-300D-C
:
: This stopped the network from going down but does not solve the DHCP
: with Building1. I could put A on its own segment but not sure if
: this will help. I plan on installing a server in each building to
: serve as file and print sharing and backup AD to ease up on the
: network stress. Bulding1 can run all of there programs, ERP,
: Internet access, File shares off of D servers and so on. Its slow
: but it works. Also I am running on a class B network but plan on
: changing it to a class C.
:
: Hope this gives you a better look at my layout.
: and thanks for your help, its been the best ever. :)

Hi Steve...

I just saw your message. That's helpful. Unfortunately I'm leaving in
about 5 minutes to head to the rodeo. I'm in Texas. I won't be able to
look into this until I return so it may be early morning before I respond.
Just giving you a head's up.

When 3COM talked about the buffer issue, were they referring to the
switching mode? I'll know more when I review these models but do you know
if these switches auto-switch between cut-thru, fragment free and
store-n-forward? Surely they wouldn't be hard set. That really wouldn't be
a buffer issue. I would describe it as a threshold. Do you know how much
traffic is on the wire or if you're getting a lot of retries?
(retransmissions) A heavily saturated line will cause these. This would
make sense to your statement of disconnecting and reconnecting but only for
a very short period. Another issue can be if everything connected is
running at Full Duplex and the backplane is unable to handle the load. This
might be what they're referring to.

I'll respond better when I return.

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose. */
Online Support for IT Professionals -
http://support.microsoft.com/servicedesks/technet/default.asp?fr=0&sd=tech
How-to: Windows 2000 DNS:
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FAQ W2K/2K3 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;291382
 
Roland Hall said:
in message
I just saw your message. That's helpful. Unfortunately I'm leaving in
about 5 minutes to head to the rodeo. I'm in Texas. I won't be able to
Click to expand...

Remember, the Bull goes on the bottom,...the Hat goes on top.
 
When the network segment would fail, the fiber link would ack like it was
stuck in a loop. Both LEDs would be fully on. In order for me to restart the
network segment I had to (1) power off one of the switches connected to this
link or (2) disconnect the fiber link for a split second. The network seem to
only fail at high loads. There are no routers or repeater in between the two
switches so the broadcasts are not getting filtered out. This problem became
more severe when new computers were added using XPPro. Any of the other
segments could fail and did at times but it was mainly the building1. It seem
like if the buildings were placed in there own broadcast domain then this
would solve the problem but I have not tried this. And this still might not
fix the original problem.


Roland Hall said:
in message
: Ok this is what I have found:
:
: All switches 3COM 3300 24/port 3C16980
: with 3C16971 100Base-FX dual module
:
: All Fiber is 6 tube 62.5/125
:
: All Patch cords 62.5/125
:
: Reference designator:
: [Letter] = Switch location
: [jn#] = Junction fiber ends Numbered
: pt = Patch cord
:
: There are 3 segments
:
: A-pt2'-[jn1]--350'--[jn2]-pt5'-B
:
: B-pt5'-[jn2]-pt10'-[jn3]--500'--[jn4]--122'-[jn5]--1000'--[jn6]--100
:
: '--[jn7]-pt10'-D
:
: E-pt5'-[jn8]--400--[jn6]--100--[jn7]-pt10'-D
:
: A,B, & C did go to the 3com switches via the fiber and those three
: went into one switch that had the server connected in to. One of the
network
: segments would fail and I had to keep unpluging the fiber and reconnect to
: get it working. 3COM said something about the buffers were overloaded.
: But now I have another device that the 3 segments terminate into a
:
: media convertor. 10/100Base-TX to 100Base-FX
: KTI Networks, KC-300D-C
:
: This stopped the network from going down but does not solve the DHCP
: with Building1. I could put A on its own segment but not sure if
: this will help. I plan on installing a server in each building to
: serve as file and print sharing and backup AD to ease up on the
: network stress. Bulding1 can run all of there programs, ERP,
: Internet access, File shares off of D servers and so on. Its slow
: but it works. Also I am running on a class B network but plan on
: changing it to a class C.
:
: Hope this gives you a better look at my layout.
: and thanks for your help, its been the best ever. :)

Hi Steve...

I just saw your message. That's helpful. Unfortunately I'm leaving in
about 5 minutes to head to the rodeo. I'm in Texas. I won't be able to
look into this until I return so it may be early morning before I respond.
Just giving you a head's up.

When 3COM talked about the buffer issue, were they referring to the
switching mode? I'll know more when I review these models but do you know
if these switches auto-switch between cut-thru, fragment free and
store-n-forward? Surely they wouldn't be hard set. That really wouldn't be
a buffer issue. I would describe it as a threshold. Do you know how much
traffic is on the wire or if you're getting a lot of retries?
(retransmissions) A heavily saturated line will cause these. This would
make sense to your statement of disconnecting and reconnecting but only for
a very short period. Another issue can be if everything connected is
running at Full Duplex and the backplane is unable to handle the load. This
might be what they're referring to.

I'll respond better when I return.

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose. */
Online Support for IT Professionals -
http://support.microsoft.com/servicedesks/technet/default.asp?fr=0&sd=tech
How-to: Windows 2000 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;308201
FAQ W2K/2K3 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;291382
Click to expand...
 
Also I have around 80 devices that use an IP address for the class B network
that I am going to change to a class C.

Steve said:
When the network segment would fail, the fiber link would ack like it was
stuck in a loop. Both LEDs would be fully on. In order for me to restart the
network segment I had to (1) power off one of the switches connected to this
link or (2) disconnect the fiber link for a split second. The network seem to
only fail at high loads. There are no routers or repeater in between the two
switches so the broadcasts are not getting filtered out. This problem became
more severe when new computers were added using XPPro. Any of the other
segments could fail and did at times but it was mainly the building1. It seem
like if the buildings were placed in there own broadcast domain then this
would solve the problem but I have not tried this. And this still might not
fix the original problem.


Roland Hall said:
in message
: Ok this is what I have found:
:
: All switches 3COM 3300 24/port 3C16980
: with 3C16971 100Base-FX dual module
:
: All Fiber is 6 tube 62.5/125
:
: All Patch cords 62.5/125
:
: Reference designator:
: [Letter] = Switch location
: [jn#] = Junction fiber ends Numbered
: pt = Patch cord
:
: There are 3 segments
:
: A-pt2'-[jn1]--350'--[jn2]-pt5'-B
:
: B-pt5'-[jn2]-pt10'-[jn3]--500'--[jn4]--122'-[jn5]--1000'--[jn6]--100
:
: '--[jn7]-pt10'-D
:
: E-pt5'-[jn8]--400--[jn6]--100--[jn7]-pt10'-D
:
: A,B, & C did go to the 3com switches via the fiber and those three
: went into one switch that had the server connected in to. One of the
network
: segments would fail and I had to keep unpluging the fiber and reconnect to
: get it working. 3COM said something about the buffers were overloaded.
: But now I have another device that the 3 segments terminate into a
:
: media convertor. 10/100Base-TX to 100Base-FX
: KTI Networks, KC-300D-C
:
: This stopped the network from going down but does not solve the DHCP
: with Building1. I could put A on its own segment but not sure if
: this will help. I plan on installing a server in each building to
: serve as file and print sharing and backup AD to ease up on the
: network stress. Bulding1 can run all of there programs, ERP,
: Internet access, File shares off of D servers and so on. Its slow
: but it works. Also I am running on a class B network but plan on
: changing it to a class C.
:
: Hope this gives you a better look at my layout.
: and thanks for your help, its been the best ever. :)

Hi Steve...

I just saw your message. That's helpful. Unfortunately I'm leaving in
about 5 minutes to head to the rodeo. I'm in Texas. I won't be able to
look into this until I return so it may be early morning before I respond.
Just giving you a head's up.

When 3COM talked about the buffer issue, were they referring to the
switching mode? I'll know more when I review these models but do you know
if these switches auto-switch between cut-thru, fragment free and
store-n-forward? Surely they wouldn't be hard set. That really wouldn't be
a buffer issue. I would describe it as a threshold. Do you know how much
traffic is on the wire or if you're getting a lot of retries?
(retransmissions) A heavily saturated line will cause these. This would
make sense to your statement of disconnecting and reconnecting but only for
a very short period. Another issue can be if everything connected is
running at Full Duplex and the backplane is unable to handle the load. This
might be what they're referring to.

I'll respond better when I return.

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose. */
Online Support for IT Professionals -
http://support.microsoft.com/servicedesks/technet/default.asp?fr=0&sd=tech
How-to: Windows 2000 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;308201
FAQ W2K/2K3 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;291382
Click to expand...
Click to expand...
 
in message
: When the network segment would fail, the fiber link would ack like it was
: stuck in a loop. Both LEDs would be fully on. In order for me to restart
the
: network segment I had to (1) power off one of the switches connected to
this
: link or (2) disconnect the fiber link for a split second. The network seem
to
: only fail at high loads. There are no routers or repeater in between the
two
: switches so the broadcasts are not getting filtered out. This problem
became
: more severe when new computers were added using XPPro. Any of the other
: segments could fail and did at times but it was mainly the building1. It
seem
: like if the buildings were placed in there own broadcast domain then this
: would solve the problem but I have not tried this. And this still might
not
: fix the original problem.

Do you know the speed/duplex of every system on the network? If not, you
should. On a Cisco switch I can look at the error logs and find out if
there are timeouts, retransmissions, etc. Since you said there are no
routers involved, I'm assuming no VLANs, so no spanning tree. We need to
know what all systems are running at (speed/duplex). We can start with one
area at a time. If the workstations are set at auto/auto, you can still
find out what they're actually running at.

I'll look at the docs and find out what the capacity is. You have several
alternatives, only one of them doesn't involve purchasing equipment.

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose. */
Online Support for IT Professionals -
http://support.microsoft.com/servicedesks/technet/default.asp?fr=0&sd=tech
How-to: Windows 2000 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;308201
FAQ W2K/2K3 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;291382
 
in message
: Also I have around 80 devices that use an IP address for the class B
network
: that I am going to change to a class C.

I don't think the IP class will make a difference.

Can you list all protocols running and specify for what purpose?
Does everyone run the same protocol(s)?
How me how all areas connect. What equipment to what equipment. I thought
at first you had one feed the next and now I'm not so sure.

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose. */
Online Support for IT Professionals -
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FAQ W2K/2K3 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;291382
 
: : > "Steve" wrote in message
: > : > I just saw your message. That's helpful. Unfortunately I'm leaving in
: > about 5 minutes to head to the rodeo. I'm in Texas. I won't be able to
:
: Remember, the Bull goes on the bottom,...the Hat goes on top.

Good to know. I'll probably save a lot of money on hats now.

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose. */
Online Support for IT Professionals -
http://support.microsoft.com/servicedesks/technet/default.asp?fr=0&sd=tech
How-to: Windows 2000 DNS:
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FAQ W2K/2K3 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;291382
 
Every device is running TCP/IP and nothing else. Switch A feeds into Switch B
via the fiber. Switch B is now feeding into the media coverter at the D
location. C feeds into a media converter at the D location and same with E.
D is the server room area. This problem has been going on for about 3 years.
My entire network seems to be getting slower and slower as more devices are
added.
 
Steve said:
Every device is running TCP/IP and nothing else. Switch A feeds into Switch B
via the fiber. Switch B is now feeding into the media coverter at the D
location. C feeds into a media converter at the D location and same with E.
D is the server room area. This problem has been going on for about 3 years.
My entire network seems to be getting slower and slower as more devices are
added.
Click to expand...

Layer 2 or Layer 3 switching (or a mix)?

Layer 2 switches must propagate all broadcasts
to the next switch, and the next etc.

Layer 2 switches are based on bridging and
suffer most of the same problems as a network
grows.
 
All the switches are layer2 switching except for one that all the segments
run into (3COM4900). However, I don't have layer3 running per say. Any
workstation in any building can see each other.
 
in message
: Every device is running TCP/IP and nothing else. Switch A feeds into
Switch B
: via the fiber. Switch B is now feeding into the media coverter at the D
: location. C feeds into a media converter at the D location and same with
E.
: D is the server room area. This problem has been going on for about 3
years.
: My entire network seems to be getting slower and slower as more devices
are
: added.

Does this imply NetBIOS over TCP/IP is not enabled? (O;=

When you're trying to minimize traffic, every little bit helps.

How many workstations are in the domain election process?
Is everyone running at 100/full? If not, do you have a breakdown?

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose. */
Online Support for IT Professionals -
http://support.microsoft.com/servicedesks/technet/default.asp?fr=0&sd=tech
How-to: Windows 2000 DNS:
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FAQ W2K/2K3 DNS:
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: All the switches are layer2 switching except for one that all the segments
: run into (3COM4900). However, I don't have layer3 running per say. Any
: workstation in any building can see each other.

Uh Steve... you said all were 3300. I assume this is now a revised
statement.

The 4900 is capable:
Ethernet switching features: Full-rate nonblocking switching on all 100/1000
Mbps Ethernet ports; full-/half-duplex auto-negotiation and flow control;
802.1Q VLAN support; 802.1p traffic prioritization

Have you seen this document?
http://knowledgebase.3com.com/consu...rchtype=normal&searchclass=&bnewsession=false

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose. */
Online Support for IT Professionals -
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How-to: Windows 2000 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;308201
FAQ W2K/2K3 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;291382
 
Steve said:
All the switches are layer2 switching except for one that all the segments
run into (3COM4900). However, I don't have layer3 running per say. Any
workstation in any building can see each other.
Click to expand...

This will explain why things slow down
as you add stations and switches.

What is your broadcast percentage?

Do you use WINS server (you should) if
if NetBIOS broadcasts are significant
percentage of the broadcasts (they will be
likely.)
 
Does this imply NetBIOS over TCP/IP is not enabled? (O;=
When you're trying to minimize traffic, every little bit helps.
Click to expand...

Yes, but even under Windows 2003 there are so
many things that need NetBIOS that is impractical
to disable it.

If one is trying to optimize such a Microsoft network
you add WINS servers instead of disabling NetBIOS.

Browsing, external trusts, some Exchange and cluster
services depencies, and a handul of other little things
don't work without NetBIOS.
 
:> Does this imply NetBIOS over TCP/IP is not enabled? (O;=
: >
: > When you're trying to minimize traffic, every little bit helps.
:
: Yes, but even under Windows 2003 there are so
: many things that need NetBIOS that is impractical
: to disable it.
:
: If one is trying to optimize such a Microsoft network
: you add WINS servers instead of disabling NetBIOS.
:
: Browsing, external trusts, some Exchange and cluster
: services depencies, and a handul of other little things
: don't work without NetBIOS.

I'm only asking questions. If he tells me only TCP/IP, then NetBIOS is not
running. I'm trying to clarify. I believe it is most likely running.

--
Roland Hall
/* This information is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose. */
Online Support for IT Professionals -
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How-to: Windows 2000 DNS:
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FAQ W2K/2K3 DNS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;291382
 
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