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PostPosted: Sat Mar 22, 2014 12:23 am 
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I'm currently working in a dreadful old building that still has mid-80's vintage AT&T LattisNet wiring, this is basically three-pair CAT3 with one pair allocated to voice and two to what was ostensibly Ethernet. I'm told It has been used for 10/100 Ethernet for at least fifteen years and works just fine with iMac's and 15" MacBook Pro's. However there is no connectivity to 13" MacBook Pro's.

If we put a switch between the wall and the machine it works, but the MAC in the 13's seem to be trying to negotiate differently .

Can anyone re-create this? All the Unibody 13's exhibit this.


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PostPosted: Sat Mar 22, 2014 8:46 am 
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No way to recreate it here, but have you tried setting Ethernet Manually?

System Preferences>Network>Ethernet>Advanced>Hardware tab or Ethernet tab depending on OSX version>Configure: Manually, Speed: 100 Base Tx or 10 BaseT


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PostPosted: Sat Mar 22, 2014 9:36 am 
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Cat3 will work for 10BaseT but 100BaseT requires Cat 5. The varieties of 100Mb Ethernet that would work with Cat3 wiring are long dead, 100BaseTX (used by the MBP and everything else with current tech) requires Cat5.

Forcing 10BaseT as BD describes should work.

More than likely it's trying to negotiate a 100BaseT connection, succeeding, then not working because of cabling. I have the same problem at work with Cat5 (not Cat5e) cabling and GigE once we upgraded the switches. It's only one section of the building but its annoying nonetheless.


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PostPosted: Sat Mar 22, 2014 11:36 am 
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I've not seen this specifically with MBPs, but have with plenty of other computer over the years where negotiation was unreliable or didn't work at all. Forcing 10baseT or even possibly half duplex 100BaseT will usually resolve the problem if the problem really is merely bad negotiation. Where manually setting the speed didn't solve it I usually, eventually, found a significant wiring fault on the affected network segment, like where someone spliced a cat5 cable by twisting apart about ten inches of each cable and then plugged them back together with telephone style button splices and shoved the whole mess back in to the wall where it would take years to find after 100/1000Mb equipment attempted to pass data through it a decade or two later. In other cases I've chased things down to bad punch downs at the patch panel, along with quite a few bad patch cables, and a couple of crap no-name switches that Just Didn't Work with certain computers.

What brand/model of switches are the computers connecting to?

- Anonymous


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PostPosted: Sat Mar 22, 2014 3:01 pm 
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The switches are ancient HP ProCurve's and there are forty other machines running at 100BaseTX over this wiring. It is just the 13" MacBook Pro's that are struggling.

This screenshot is from my 15" MacBook Pro:

Image

On the 13's setting it manually just gives an error that the cable is connected but the interface has no IP address, set a manual IP address and there is still no connectivity.

This building isn't going to have another cent sunk into it, a demolition clause is dangling over it's head and everyone can be evicted with 90 days notice.


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PostPosted: Sat Mar 22, 2014 3:18 pm 
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I know they're supposed to be Auto-switching, but do you have a Crossover cable to try on one?


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PostPosted: Sat Mar 22, 2014 8:30 pm 
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That behavior is consistent what what I've observed from time-to-time with something flaky on the network as well as with incorrect auto-configuration (that can occur for other reasons), but lots of things could do it.

Do you have anything else configured oddly on the network? VLANs? Unusual frame size? Weird authentication protocols? Some other strange managed switch configuration settings? Funky port settings on the switch? Does the switch show a link light?

If you put another switch on the opposite end of the network (plug the alternative -- unmanaged -- switch in and patch line running to the MBP through that switch) does the problem go away?

If you boot off an external drive with fresh install of OS X does the problem persist? If you plug a 13" MBP directly in to one of the HPs through a 4-wire patch cable do you still have the problem?

- Anonymous


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PostPosted: Sun Mar 23, 2014 12:06 am 
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He already mentioned that installing a switch in-line brings it back to life.

Unfortunately I was afraid they were HP switches. HP switches in my experience have a dreadful tendency to not work if you try to force operation at a particular speed. The only way around it is to configure the switch port to run the same speed as the client.

I second Anon's suggestion to try a cable that's only got the two pair in it. If there's anything unusual about the other four contacts, this would isolate them from the client.


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PostPosted: Sun Mar 23, 2014 12:29 pm 
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Testing a different switch on the other end will isolate the problem to the wiring vs switch.

Also, when manually configuring, try setting half duplex as manually configured full duplex may confuse the HP.

- Anonymous


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PostPosted: Sun Mar 23, 2014 5:25 pm 
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This isn't my network (client site) so I can't speak with too much authority, but it is by all outward appearances pretty simplistic. There is a Netgear ProSafe firewall connected to two HP ProCurve switches. They are managed switches but I doubt they're configured as anything other than factory default.

Although I don't think anyone would characterize running Fast Ethernet over Reagan era telephone cable is a "best practice", I'm told these 13" MacBooks are the first instance of a problem. So I don't think it is a switch or cabling problem. Any port in the office will show the same behavior with the 13" MacBooks while working with anything else.

I have a four pin cable from an old WiMax modem I am going to test directly though. And yes, the switch lights up when the 13 is attached.


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