Switch is blocking a specific connection

[jallison86]

I'm having a frustrating networking problem. I can work around it, but it bothers me that I don't understand why this is happening.

The basic problem is that my Windows 7 desktop cannot establish a connection to an Ethernet-connected sprinkler controller (specifically an Etherrain 8). Actually, it can establish a connection, but only when I take a Linksys 5-port switch out of the equation. The setup that works has three Linksys 8-port switches, each of which connects back to the router. The Windows PC is connected to one of these switches, the Etherrain to another. This works fine.

What breaks this is when I introduce a 5-port Linksys switch. Due to physical realities it'd be nice to have this 5-port switch next to the Windows PC. But when I connect the Windows system to this switch, I can no longer access the Etherrain. I can access an IP camera that is connected to the same switch as the Etherrain. Doing a tracert to the Etherrain's IP address simply gives a timeout.

I've power cycled all the switches and the router. I've cleared the arp cache on the Windows PC. I don't understand why putting an extra switch in the network blocks communication to this one device. Any thoughts?

Thanks.

- Jeff

 

[kanewolf]

Have you set a static IP address on the Etherrain?

 

[jallison86]

I haven't tried a static IP. I'll try that although I admit I don't understand why it would make a difference.

Thanks.

- Jeff

 

[kanewolf]

I haven't tried a static IP. I'll try that although I admit I don't understand why it would make a difference.

Thanks.

- Jeff

I agree, I don't either. But for something like that device, a static IP address is usually the best implementation anyway.

Can you upload a quick diagram of the two configurations?

 

[jallison86]

Not sure how to upload here, but here are two pictures. works.jpg [https://dl.dropboxusercontent.com/u/141140/Works.JPG] shows the working configuration and doesnt work.jpg [https://dl.dropboxusercontent.com/u/141140/Doesnt%20Work.JPG] shows the configuration I'd like to use but that does not work. Sorry for the poor drawings, but I just threw these together in about two minutes.

 

[Ralston18]

Jallison, Kanewolf,

I have been following this post out of general interest and curiousity.

Has the problem been resolved? If so what was the resolution?

I was wondering about tracert - would running traceroutes between the Windows PC to both the Etherrain and the IP camera be of value?

E.g., run tracet from Windows PC (and/or the Windows 7 Box) to first the IP camera and then again immediately to the Etherrain. First in the Works picture and then again in the Doesnt Work picture. Then compare the paths and times.

Probably that has been done but I am just wondering if comparing tracert information with and without the 5-port switch (or similiar situation) would be useful tool. Albeit a bit tedious perhaps.....

Or would the packets just be routed all around via different network paths to the point of making the exercise moot?

Again just trying to learn something.

Thanks.

 

[jallison86]

No, it hasn't been resolved. I have run tracert. It times out when trying to get to the Etherrain but returns "<1 ms" results when going to the IP camera. This with the 5-port switch in the mix. Without that switch I get "<1 ms" results for both.

I assigned a static IP for the Etherrain but it hasn't made any difference. When time permits I'm going to swap out the 5-port switch for a known good switch that is currently elsewhere in the network. That requires some rewiring and hence some free time. If *that* doesn't work then I'll just run a new cable from the router location to the desktop/laptop location. That's a simple and obvious solution but there's a doorframe in the way so it's not a great look.

Thanks all for input here. I'm mystified as to why this is happening (unless there's just some hardware problem in the 5-port switch, which I'll eliminate soon).

- Jeff

 

[Ralston18]

Jeff,

Thanks. Very interesting.... Appreciate your getting back to me.

Selecting different ports on the 5-port switch and eventually swapping out the 5-port switch should certainly help narrow things down.

What Linksys Model Switches (5 and 8 port) are in use and how populated (number of ports in use) are the switches? The reason for the question is that some of the models do not allow use of both the uplink port and the adjacent port as they are wired together. Not sure of the end consequenses per se (to be honest) but bizzare/unexplainable behavior is not at all uncommon with such things.

Just let me know. Thanks.

Take care,

Ralston18