Network gurus - bizarre wiring problem

Factual Questions
1

I’m doing a setup at a hotel. ATT has installed a dedicated point to point T1 line for us, in theory connecting a workroom at the hotel to our office a few blocks down the way.

Both ends of the line have been tested, loopback is fine and our systems folks can see the Cisco router that we’ve got here at the hotel.

If I plug a little Netgear switch into the Cisco router (down in the hotel’s cable closet) and hook my laptop up to it, bingo I’m connected right to our nearby office, no problems. That’s exactly how it should work.

However if I run a line to the hotel’s patch panel to light up the jack in our workroom at the hotel, I can’t get a connection. Can’t even get DHCP from the router.

I know that we’ve got the right port on the patch panel and the wiring appears to be fine (since plugging the hotel’s broadband line into the same port puts me online in the workroom, no problems. In fact that’s how I’m typing this now).

Checked every cable in use, they are all fine. The hotel’s broadband comes out of a router like ours, plugs into a plain old Cisco 2950 switch and then into the patch panel - nothing unusual there that I can see.

So my best bet is that there is “something” inbetween the patch panel and the hotel workroom that is somehow filtering out our traffic (or any non-hotel traffic). I spent several hours with the building guys yesterday, including checking the cable closets on the intervening floors to see if we could find any kind of mysterious box inbetween, nothing that we could see.

The hotel is checking with the folks who set up the wiring originally but anyone got any ideas what else might cause this?

I’m baffled. At least room service is good and the company will pick up the minibar tab :smiley:

2

Do you know that there’s something in between? If I suspected extra hardware, I’d hook up something in that has a light to indicate a connection, then disconnect the other end. If the light stays on, hardware confirmed.

If it goes out, then… :confused:

:smiley:

3

If I understand correctly, you have a T1 run into the hotels wire closet. The T1 is a PtP link between the hotels closet and your home office. You have a CISCO router (presumably with a DSU/CSU card or an external CSU/DSU appliance) that connects the T1 to the router. This all tests out. You can get into the router and ping not only the gateway (probably another router) at the far end but you can ping devices on your office network as well…correct?

Moving on, when you connect a switch to the router and plug in a laptop you have connectivity to your home office from the hotel…and I assume vice versa (i.e. you can ping devices on your home office from the laptop in the hotel, and you can ping the laptop from a computer or device at the home office)…again, is this correct?

Assume I’m right in my interperetation of what you are saying so far, the problem occurs when you attempt to plug into the hotels infrastructure via a patch pannel in the wire close…correct?

Ok…again, assuming I have all this down, your problem is obviously with the hotels infrastructure…so you can eliminate the T1, and the routers at both ends. Do you know what device the port you are patching into actually goes into…or do you assume its simply a home run to where ever you are trying to get too (i.e. does the port in the patch pannel go into the hotels switch, perhaps a DMZ on the hotels firewall, or is it simply a line to another patch pannel somewhere else in the hotel)?

If its either of the former (a switch or DMZ) then your problem is probably a routing issue…or maybe a NAT issue. You said you couldn’t get DHCP…is it your intention to get DHCP from the hotel, are you serving it up via the router (I think CISCO does this), or do you have an appliance or server serving it up for you? How about DNS?

If its the latter (i.e. if its a straight through home run from whereever you are trying to get too to the patch pannel), then (assuming you are getting a link light) I’d put a Sniffer or a Fluke meter on it and see what you are getting signal wise. Could be some kind of IP issue (i.e. maybe its something as stupid as you don’t have DHCP set up right, or you aren’t serving up the right IP network to allow connectivity…I’ve done this myself many times and then gone :smack: ).

Not sure if any of this is helping you, but if you can give some more detail I can probably help you work it out if you like. Or someone else who can write better than I may be along to help out. :stuck_out_tongue:

-XT

4

[QUOTE=xtisme]
If I understand correctly, you have a T1 run into the hotels wire closet. The T1 is a PtP link between the hotels closet and your home office. You have a CISCO router (presumably with a DSU/CSU card or an external CSU/DSU appliance) that connects the T1 to the router. This all tests out. You can get into the router and ping not only the gateway (probably another router) at the far end but you can ping devices on your office network as well…correct?
[/QUOTE]

That’s correct. Exact topology is ATT biscuit->my router (internal card)->patch panel (or my router->my switch->patch panel, tried both ways).

[QUOTE=xtisme]
Moving on, when you connect a switch to the router and plug in a laptop you have connectivity to your home office from the hotel…and I assume vice versa (i.e. you can ping devices on your home office from the laptop in the hotel, and you can ping the laptop from a computer or device at the home office)…again, is this correct?
[/QUOTE]

Yes.

[QUOTE=xtisme]
Assume I’m right in my interperetation of what you are saying so far, the problem occurs when you attempt to plug into the hotels infrastructure via a patch panel in the wire close…correct?
[/QUOTE]

Yup.

[QUOTE=xtisme]
Ok…again, assuming I have all this down, your problem is obviously with the hotels infrastructure…so you can eliminate the T1, and the routers at both ends. Do you know what device the port you are patching into actually goes into…or do you assume its simply a home run to where ever you are trying to get too (i.e. does the port in the patch pannel go into the hotels switch, perhaps a DMZ on the hotels firewall, or is it simply a line to another patch pannel somewhere else in the hotel)?
[/QUOTE]

Well at this point it sure looks like from the patch panel to the workroom it’s a straight shot, simply because we were not able to find anything inbetween by checking other cable closets on the intervening floors. However it’s not my building or my wiring so I can only judge by what I see.

That being said, given that the problem only occurs when plugging into the hotel’s patch panel I am assuming that there is something handling traffic inbetween those two points because I don’t know what else could cause this to occur. I did think that maybe we were pushing the limits of CAT5 distance (the ATT biscuit is hooked up to our router with a 50’ cable, necessary due to the physical setup of their closet) so I hooked up the hotel’s broadband to our workroom using a 100’ cable rather than a 3’ cable and it still works like a charm.

[QUOTE=xtisme]
If its either of the former (a switch or DMZ) then your problem is probably a routing issue…or maybe a NAT issue. You said you couldn’t get DHCP…is it your intention to get DHCP from the hotel, are you serving it up via the router (I think CISCO does this), or do you have an appliance or server serving it up for you? How about DNS?
[/QUOTE]

Our Cisco router handles DHCP and since it’s a PtP connection to our regular office, DNS is handled by our corporate DNS. If one of my machines won’t get DHCP then it’s not speaking to the router (and I know that DHCP is working fine on the router since hooking stuff up to it any path other than over the hotel wiring is fine).

[QUOTE=xtisme]
If its the latter (i.e. if its a straight through home run from whereever you are trying to get too to the patch panel), then (assuming you are getting a link light) I’d put a Sniffer or a Fluke meter on it and see what you are getting signal wise. Could be some kind of IP issue (i.e. maybe its something as stupid as you don’t have DHCP set up right, or you aren’t serving up the right IP network to allow connectivity…I’ve done this myself many times and then gone :smack: ).
[/QUOTE]

Unfortunately I don’t have a Fluke (or training on same darnit!) but I’ll see if the local office has one or perhaps the hotel (they contract their IT out to a big 3rd party). Excellent idea.

[QUOTE=xtisme]
Not sure if any of this is helping you, but if you can give some more detail I can probably help you work it out if you like. Or someone else who can write better than I may be along to help out. :stuck_out_tongue:

-XT
[/QUOTE]

Thanks for the ideas!

5

You guys are levels and levels above me re networking knowledge so I hesitate to say anything, but just to throw one thing in… a few years ago we had a similar sounding hangup when the network engineers were wiring our offices and were stumped by our office patch panel’s non-response (they had no test gear with them that day) it turned out the misbehaving aspect was that the patch panel (for whatever reason) was connected with a “reversed” CAT 5 cable from whatever feed point it attached to and this screwed up other things interfacing to it.

6

[QUOTE=astro]
it turned out the misbehaving aspect was that the patch panel (for whatever reason) was connected with a “reversed” CAT 5 cable from whatever feed point it attached to and this screwed up other things interfacing to it.
[/QUOTE]

You are talking about a cross over cable. Its a good point, except that you wouldn’t get a link light if it was cross connected (assuming its a DTC to DTE connection obviously)…and I assume since this is the first thing anyone would check that there IS a link light. If the OP hasn’t check it though, the first thing to do is see if there is a link light…if so then you have basically connectivity, so its something else.

-XT

7

[QUOTE=Valgard]
That being said, given that the problem only occurs when plugging into the hotel’s patch panel I am assuming that there is something handling traffic inbetween those two points because I don’t know what else could cause this to occur. I did think that maybe we were pushing the limits of CAT5 distance (the ATT biscuit is hooked up to our router with a 50’ cable, necessary due to the physical setup of their closet) so I hooked up the hotel’s broadband to our workroom using a 100’ cable rather than a 3’ cable and it still works like a charm.
[/QUOTE]

(just as an aside, I usually call the ‘bisquit’ a ‘smart jack’. :))

The reason I’d doubt it was a problem with the patch cord from the smart jack to the router is that you’ve already said you have connectivity from the router to your home office…which means the problem doesn’t seem to be from the router ‘out’, but from the router ‘in’…if that makes sense. So, I would definitely concentrate on the router inward (i.e. toward the hotels infrastructure).

[QUOTE=Valgard]
Our Cisco router handles DHCP and since it’s a PtP connection to our regular office, DNS is handled by our corporate DNS. If one of my machines won’t get DHCP then it’s not speaking to the router (and I know that DHCP is working fine on the router since hooking stuff up to it any path other than over the hotel wiring is fine).
[/QUOTE]

Have you done an ipconfig /all (I assume your comuters are using Windows…if not use whatever command you need for the OS you are using that is equivelent) to see what, if anything, you are getting? Its possible that you are getting the HOTELS DHCP/DNS combo…which is probably different than whatever you are serving up on the router. If you are getting no DHCP at all, try this. Put a static address/subnet mask on your computer from the routers local network (obviously make sure its unique :)) and see if you can now ping the router. If you can then something is blocking DHCP from the router (or DHCP is somehow set up incorrectly…doubtful since you said you put a machine on a switch locally to the router and it worked, but still worth looking into).

[QUOTE=Valgard]
Thanks for the ideas!
[/QUOTE]

No worries. :slight_smile: Always glad to help, and I actually like doing this stuff.

-XT

8

What’s the length of cable between your end PC and the router? Cat 5+ have maximum lengths of 100m.

9

[QUOTE=xtisme]
The reason I’d doubt it was a problem with the patch cord from the smart jack to the router is that you’ve already said you have connectivity from the router to your home office…which means the problem doesn’t seem to be from the router ‘out’, but from the router ‘in’…if that makes sense. So, I would definitely concentrate on the router inward (i.e. toward the hotels infrastructure).
[/QUOTE]

I concur :slight_smile:

[QUOTE=xtisme]
Have you done an ipconfig /all (I assume your comuters are using Windows…if not use whatever command you need for the OS you are using that is equivelent) to see what, if anything, you are getting? Its possible that you are getting the HOTELS DHCP/DNS combo…which is probably different than whatever you are serving up on the router. If you are getting no DHCP at all, try this. Put a static address/subnet mask on your computer from the routers local network (obviously make sure its unique :)) and see if you can now ping the router. If you can then something is blocking DHCP from the router (or DHCP is somehow set up incorrectly…doubtful since you said you put a machine on a switch locally to the router and it worked, but still worth looking into).
[/QUOTE]

Oh yes, that’s one of the first things I checked. These are all W2K boxes and when I plug our router into the patch panel the PCs all get that autoconfig class B address that the OS assigns when it can’t reach a DHCP server (169.254.x.x).

[QUOTE=Quartz]
What’s the length of cable between your end PC and the router? Cat 5+ have maximum lengths of 100m.
[/QUOTE]

Quartz, I did consider that. Since the only difference in line length between the hotel’s T1 and my T1 is the extra 50’ of cable from the biscuit to my router, I tried my afore-mentioned test which was to patch the hotel’s T1 line in using a 100’ cable. If my 50’ cable is enough to hit the limit then adding 100’ to the hotel would certainly do it. No effect - the hotel’s T1 still works over the patch panel just fine.

Hotel IT guy is here, we’re going to see if we can find a crossover cable and use that to patch in (I was thinking about it the other day) however I consider this a long shot…all of the switches I am using (at both ends) are autosensing for reversed pairs - you can patch them in with a crossover cable and they will automatically correct for it.

Definitely my Sherlock Holmes weekend. To break the monotony I went for a nice walk in downtown LA and was a frontline witness to two car crashes in 30 minutes, one a fender bender and the other a high-speed hit and run which tore the bumper off a car (containing a couple and their two young daughters) and threw it into a guy’s head. I feel safer a few floors above street level now.

10

What about the Cisco 2950 switch itself. Can you put ACL’s (access lists) in the
switch itself to filter traffic? I know it wouldn’t make since to not have an ACL in
the router, but you were able to connect directly through the netgear switch
to router, so you were not filtered out in the router. But when you went though
the Cisco switch … no go.

In the stuff on-line it looks like Cisco 2950’s have can be programmed with ACL’s

11

[QUOTE=EnderWay]
What about the Cisco 2950 switch itself. Can you put ACL’s (access lists) in the
switch itself to filter traffic? I know it wouldn’t make since to not have an ACL in
the router, but you were able to connect directly through the netgear switch
to router, so you were not filtered out in the router. But when you went though
the Cisco switch .. no go.

In the stuff on-line it looks like Cisco 2950’s have can be programmed with ACL’s
[/QUOTE]

I don’t think that the 2950 enters into it - that is the hotel’s equipment which is used to share out their T1 line. Their router is plugged into their 2950, then their 2950 is used to activate ports on their patch panel. That works just fine. The problem arises when we do not use their stuff at all (other than their patch panel).

12

You can also try dropping the link speed in the laptop’s adapter configuration to 10 Mbps, half duplex. If it starts working, then you have good evidence that the wiring is not up to spec. Also, if Nanodia’s suggestion indicates an intermediate device, it’s probably a layer 3 or higher device, since DHCP can’t cross subnets.

13

[QUOTE=Valgard]
Oh yes, that’s one of the first things I checked. These are all W2K boxes and when I plug our router into the patch panel the PCs all get that autoconfig class B address that the OS assigns when it can’t reach a DHCP server (169.254.x.x).
[/QUOTE]

Hm…thats strange. Unless of course the hotel isn’t serving up DHCP (maybe they are using statics for instance), which would be a bit strange in itself. Or maybe your connection IS doing a homerun from the patch pannel to the wall plate you are trying to get too.

By any chance, did you try my suggestion of putting a static on the PC and then see if you can ping through to the router? If so, what was the result?

Unfortunately, if its a layer 1 issue (and its sounding like it is), you really need something like a Fluke meter to test out the connection. You are getting a link light, and are sure the link light you are getting is the proper one? Have you tried to use walkie talkies and have someone do something as prosaic as plug and unplug the connection at the patch pannel and see if the PC’s LL flashes on and off?

-XT

14

[QUOTE=Cleophus]
You can also try dropping the link speed in the laptop’s adapter configuration to 10 Mbps, half duplex. If it starts working, then you have good evidence that the wiring is not up to spec. Also, if Nanodia’s suggestion indicates an intermediate device, it’s probably a layer 3 or higher device, since DHCP can’t cross subnets.
[/QUOTE]

That CAT switch should autosense the line and bring it down if there is a problem with the line. IF he’s getting a link light then there is at the minimum enough connectivity there to drop the line speed automatically to a lower, working speed. Personally though I’m also leaning towards some kind of layer 1 issue as well…but the link light is the stumbling block there. Its been pretty rare in my own experience that when you get a link light you get no connectivity at all (I can think of a few things that could cause it, but it would be pretty low orders of probability IMHO).

My own first thought was that he was going through the hotels infrastructure…but I can’t imagine they wouldn’t be serving up DHCP on their net. Unless he’s actually in the hotels DMZ, or something like that…in which case you’d be right about DHCP not getting through (you CAN pass DHCP over a different subnet, but you need to punch a hole for it through the firewall, or work some other magic if you are going through a router).

-XT

15

BTW, when you finally work out the problem I’d appreciate it if you’d post it here…I’m curious what it turns out to be in the end. :slight_smile:

Oh, and GL…hope you don’t have to work all weekend like I am (have a crashed firewall on my hands…its pretty ugly atm).

-XT