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Network jack not working with switch but ok with 1 pc

D

dct14

Junior Member
Odd issue... we run 1G network

when a user in an office plugs in to jack their PC gets 100mbps (not 1g)... that is ok but don't know why.

Cable does not exceed more than 70 feet from main switch to jack.

In past i had placed a Cisco SD205 switch and split network for 2 computers... it worked well for a while.

Now when i plug in switch the computer does not recognize a plugged in cable but computer directly to jack still gives 100mbps connection.

Any one have any ideas as to why and how to correct?

The switch was tried on another jack in different office and it works fine. Seems to be related to that one jack.... how can I troubleshoot
 
Take the faceplate off the wall, remove the jack, and re-punch all 4 pairs (8 strands), then try again. If it still doesn't work, re-punch on the patch-panel (or jack, whichever you have) at the other end.

It sounds like you've got a layer 1 problem. If re-terminating the pairs doesn't fix it, then you'll probably need to run a new cable to that location.
 
Odds are the cable is terminated as T-568A and the jack is terminated as T-568B or vice versa. That would result in Fast Ethernet speeds instead of Gigabit on the computer. Or full gigabit with the proper firmware support.

On the switch, same deal, except it can result in zero connection.

It really just depends on how each interprets the other. In general, you want the same cable and jack termination through out your network and it sounds like it is incorrect somewhere. It could also be that the jack is the wrong termination type for the rest of the network cables AND its also improperly terminated with a loose connection.
 
Yep as seepy posted, check the physical pinouts on both sides of the cable termination as either something has come loose, it's wired wrong or something similar. Gig PHY uses auto-mdix so whether it's done in A or B really shouldn't matter.
 
kevnich2 said:
Yep as seepy posted, check the physical pinouts on both sides of the cable termination as either something has come loose, it's wired wrong or something similar. Gig PHY uses auto-mdix so whether it's done in A or B really shouldn't matter.
Click to expand...

I see people saying Gig PHY uses auto-mdix all the time. But no, it does not. It is an optional part of the standard. You can, and will, find devices that don't do it, mostly because it saves $0.50 or so a port, so why not increase my profit margin?

Though if it's coming up as 100Mbit, that sounds like the cable is completely wired incorrectly, as it would mean only 2 pairs are correct(100BaseTX only uses 2 pair). As mentioned, redo the ends.
 
TheCrackLing said:
I see people saying Gig PHY uses auto-mdix all the time. But no, it does not. It is an optional part of the standard. You can, and will, find devices that don't do it, mostly because it saves $0.50 or so a port, so why not increase my profit margin?

Though if it's coming up as 100Mbit, that sounds like the cable is completely wired incorrectly, as it would mean only 2 pairs are correct(100BaseTX only uses 2 pair). As mentioned, redo the ends.
Click to expand...

According to the wiki article on it

"Subsequently, Dove promoted auto-MDIX within the 1000BASE-T standard[5] and also developed patented algorithms for "forced mode auto-MDIX" which allow a link to be automatically established even if the port does not auto-negotiate.[6] This may or may not be implemented on a given device, so occasionally a crossover cable may still be necessary when connecting auto-MDIX to MDIX (hub or switch), especially when autonegotiation is deactivated.[7] Newer routers, hubs and switches (including some 10/100, and all 1 Gigabit or 10 Gigabit devices in practice) use auto-MDIX to automatically switch to the proper configuration once a cable is connected. The other four wires are used but are not crossed since auto-MDIX is mandatory at the higher data rates (1000BASE-T transmits and receives on all pairs simultaneously without any dedicated send/transmit pairs)."

http://en.wikipedia.org/wiki/Medium_Dependent_Interface
 
How wrong they are.

http://en.wikipedia.org/wiki/1000baseT#1000BASE-T

Automatic MDI/MDI-X Configuration is specified as an optional feature in the 1000BASE-T standard,[12]

[12]Clause 40.4.4 in IEEE 802.3-2008

Now I'm going to believe in IEEE 802.3-2008 more so than wikipedia.

Also, I'm going to believe in my experience where Cisco's early switch linecards for Gigabit were not auto-mdix. The Cisco 6100 Series Gigabit Line cards for the 6500/7600s were not auto-mdix from my experience.
 
You can have one other issue, proper 'cable' or color termination, in itself, does not guarantee being cat 6, if your jack/cable test out to a lower cat, you will only run at the lower speed.
 
I would check the port on the switch connected to it. 100Mbps would be fine on the laptop if it didnot have 1Gbps NICs. Many don't.

I am betting your switch issues are software related.
 
alkemyst said:
I would check the port on the switch connected to it. 100Mbps would be fine on the laptop if it didnot have 1Gbps NICs. Many don't.

I am betting your switch issues are software related.
Click to expand...

I'm thinking they're running unmanaged switches, because if they had someone with the knowledge to program a switch, then he/she would have already checked the port config.

OP - what make/model switch are you using?
 
seepy83 said:
I'm thinking they're running unmanaged switches, because if they had someone with the knowledge to program a switch, then he/she would have already checked the port config.

OP - what make/model switch are you using?
Click to expand...

Assuming it was communicated. A lot of times this is a person just looking to connect their own switch in their office/area and port security shuts it down.

Being that that laptop connects fine, I am thinking that is the issue.

If the laptop was a 1gig NIC then I'd point to wiring if it's only connecting at 100Mbps esp if at half duplex or had other problems.

Before rewiring, that's what I'd verify.
 
RadiclDreamer said:
According to another site

22 Aug 02 Approved 40.4.4 1000BASE-T Auto-crossover

http://ieee802.org/3/interp/index.html

I tried to check the ieee website but they are behind a paywall.
Click to expand...

Automatic MDI/MDI-X Configuration is intended to eliminate the need for crossover cables between similar devices. Implementation of an automatic MDI/MDI-X configuration is optional for 1000BASE-T devices. If an automatic configuration method is used, it shall comply with the following specifications. The assignment of pin-outs for a 1000BASE-T crossover function cable is shown in Table 40–12 in 40.8.
Click to expand...
Emphasis is mine.

http://standards.ieee.org/getieee802/download/802.3-2012_section3.pdf

Not behind a paywall if used for academic purposes.
 
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