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Why can't I use the 10/100 MB switch instead of the direct ethernet cable?

Posted on 2011-09-19
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I manage the IT for a group of buildings that have CAT5e going between them.  The main office has the Internet connection (DSL) modem, connected to a router.  The router has a 16 port 10/100 dumb switch off it (switch a).  A cable is then ran to each of the other buildings and the cables are connected to switch a.

At one of the other buildings, a Dell optiPlex Gx755 connects to the cable from the main office.  When the cable is connected directly to the OptiPlex, the OptiPlex has a 10 mbps connection.  If I add a 10/100 linksys dumb switch (switch b), connect the main office CAT5e to it, and use a 5' CAT5e cable from switch b to the OptiPlex, the NIC can't get doesn't get any connection.  The DHCP client address is a 169.x.x.x address instead of a 192.x.x.x address.  Even if I assign a static address to the OptiPlex while it's connected to switch b it still doesn't connect to the Internet, nor can I ping anything.  
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Question by:ehess
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by:Jacobfw
ID: 36562262
Are you using a normal network cable to connect the two switches or a cross-over CAT5 cable?
Some switches can auto-sense and adjust, but most dumb switches require the use of a cross-over cable.
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by:emilgas
ID: 36562330
That cable is a cross-over switch you need a straight through, can you clarify where that cable connects to on the other end?
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by:rindi
ID: 36562409
The LEDs on the switch should also tell you if the connection is good. How far apart are the two switches? The limit of Ethernet would be around 100 meters. If the cable isn't good quality or if it isn't properly attached to the connector, the distance will be reduced. You may have to locate the 2nd switch closer to the first switch to get a proper signal.
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by:pjam
ID: 36562605
169.x.x.x sounds like it is coming from the NIC or the linsys, and not DHCP.
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by:emilgas
ID: 36562716
169.x address is a generic ip address scheme that is assigned  by the operating system when there is no ip address
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by:rindi
ID: 36562740
It's called "Apipa"
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by:emilgas
ID: 36562769
There you go that was the word I was looking for actually the abbreviation
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by:ehess
ID: 36563377
the cable that is going between switch a and switch b is a straight through switch.  Neither of the swtiches are managed switches.  The distance is less than 500 feet, not sure if it's under 300 feet.  
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by:shahravish
ID: 36563395
If you are getting a connected link on the PC, it sounds like the connection from the other building (switch a) to switch b is not working. Are you able to see any activity on the switch to confirm the link is active?
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by:Jacobfw
ID: 36563965
Switch B (newly added dump switch), may have a specific port for up/down link and/or a switch beside one of the port to allow for switching between cross over/straight cable.  Can you provide the make/model of this dump switch?
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rindi earned 500 total points
ID: 36565066
300 feet would be close to 100 meters, and 500 feet is around 150 meters, so you probably are way above the specification limits of ethernet. Also remember that if the theoretical distance is 90 meters, the cable itself usually will be longer as you can hardly ever use a straight cable between points a and b, but rather have to go around obstacles etc that make the cable longer. The reason you get a signal of 10mb max on the PC is that you are at running at the limits, and your NIC may just be good enough to use the signal, while the cheap switch's NIC isn't good enough.

Put the switch half way between point a and b, and then you'll probably get 100mb, or use a wireless bridge between the buildings.
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by:ehess
ID: 36566785
The cable going from the switch a to switch b is very close to 300 feet.  Normally I see an uplink label on the dumb switches requiring the uplink cable to be in a specific port.  I have tried two switches.  

I didn't document the light flashing activity exactly when I was at the location, but I recall the following.
When the D-Link DSS-5+ was connected, the uplink light was solid red. The PC port flashed fast while the DHCP address was assigned then went off completely, no light.  Initially when either switch was connected the computer had the full potential 1 GB or 100 MB, but only for a second.  Then the DHCP address was assigned and nothing.  Just Windows icon for no Internet access on the NIC status.  

Linksys Gigabit 5-port Workgroup Switch
Model: EG005W

D-Link 10/100 Fast Ethernet Switch
Model: DSS-5+

I've requested with our crew member who ran the cable for me to put connectors on the cable at a distance closer to the switch a builidng, still within the building where switch b is currently.  Once this is done I'll update the case.  
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by:ehess
ID: 36566791
adding to the last post...
I'll put swtich b closer when the cable has been changed, then I'll update the posting.
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by:Jacobfw
ID: 36567268
D-Link 10/100 Fast Ethernet Switch
Model: DSS-5+

The DSS-5+ is truly a Plug & Play switch, and installation is as easy as 1-2-3. All ports support Auto-MDI/MDI-X, which means whether it is connecting to another switch or to a computer, there is no need for crossover cables

Linksys Gigabit 5-port Workgroup Switch
Model: EG005W

Five auto-sensing ports designed to automatically deliver optimal Ethernet or Gigabit speeds for each connected device and eliminate the need for MDI/MDI-X crossover cables.

Looks like both switches have auto-sensing ports, so cross-over cable is likely not the problem.
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by:ehess
ID: 36588772
I ordered a LevelOne Industrial PoE Switch IFE-0502 and am waiting for it to arrive.  I don't have power at the buidling where I'll add it for a shorter cable run to switch b.  
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by:ehess
ID: 37019915
The switch that I ordered wasn't the right one.  I have no power supply available at the location where I need to put the new switch to make the distance shorter.  What switch can I use that doesn't require a power supply directly connected to it?  I only need a 5 port 10/100 switch.  
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by:Jacobfw
ID: 37019966
you can use something like this
http://www.nextag.com/Veracity-VOR-ORQL-OUTREACH-774622465/prices-html

remember you need to have PoE supplied to this unit, so you either must have a PoE switch at your main closet or an inline power source at the closet on that line.
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by:ehess
ID: 37020234
Thanks for the quick response, I'll get it ordered.
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by:ehess
ID: 37347314
I setup the new PoE switch and a shorter cable run.  Still didn't get a good signal.  Finally pinpointed a bad wiring job on the connector at the second shop location.  All's working now that the connector was redone.
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