Solved: Problem with small network...help!

chris-sexton · ‎08-16-2010

Hello there,

Ok, I manage a very small network in my wife's vet clinic. This network was working correctly for me for over a year with no issues...It is very, very basic. I replaced a wireless router, and now It is completely futzored!

Here's what I have:

1 Actiontec DSL Modem (with wi fi and a 4 port switch built in)

connected via cat5 to to the internet port on

1 Linksys BEFSR81.

Ok, now the Actiontec modem provides internet access.

Connected to the linksys BEFSR81 is:

1 Netgear Wireless router (new, working fine)

3 windows workstations (1 acts as an internal server, the others are merely workstations)

1 Canon printer

The ideal situation is that any computers connecting to the network either directly plugged into the BEFSR81 or via wi fi (through the Netgear router), should be able to see the internal server AND they should be able to access the internet. This is not happening.

The machines connected to the BEFSR81 can see the internal server, but have no internet access.

Any machine that connects directly to the Actiontec modem (via its own wireless) can see the internet, but not the BEFSR81 or anything connected to it.

I am suspecting a problem with the communication between the BEFSR81 and the Actiontec, but I can't seem to confirm. I have tried just about every possible configuration of DHCP, CNS, UPnP that I can on both of these devices. I am at wits end. Unfortunately, it does have to be fixed. The server has equipment tied to it that use the internet to file test results. If we can't use the equipment like that, we have to send our tests out, and that is much more expensive for us. So each test that goes out is money I am losing the clinic.

The lab machines only need internet access. There is no configuration (they can be remotely configured by the company we lease them from), and they needed 0 setup when installed. but they can't see the internet right now.

I will of course monitor the thread closely and answer any questions, but basically, I am totally lost now. Any ideas would be appreciated, and may move me forward.

Thanks!!

Atif Awan · ‎08-18-2010

Hmm ... So if you have DHCP off on linksys and are only using its switchports with Actiontec plugged into one of the switchports itself, any clients connected to the switchport should just be able to get IP Address via DHCP from Actiontec. If this does not work it is time to look deeper and see what the MACs being learnt are (looking at ARP cache on the hosts) and possibly take sniffer captures.

As a starting point I would suggest you disconnect the Netgear for the time being and bring the configuration on devices back to the original working config (NAT/DHCP on Linksys). Next connect the Actiontec cable to Linksys WAN port and verify the WAN port is getting an IP Address from Actiontec. Once this is confirmed connect a laptop to Linksys switchport and verify it gets an IP Address from Linksys. If that works then from this laptop ping the Actiontec IP Address and after this is a success then try browsing for internet. If internet browsing does not work verify DNS. If you are able to make all of this work then Netgear can be introduced back into the equation to see if connectivity remains as desired.

View solution in original post

Peter Paluch · ‎08-17-2010

Chris,

Please try to provide a brief picture of your network - a quick-and-dirty schema of what your individual devices are and how are they interconnected. Please also include the clients so that it is easier to visualize where does the traffic "stop". And also please have the IP addressing indicated in the exhibit. This will help us to narrow down the source of your problems.

Best regards,

Peter

chris-sexton · ‎08-17-2010

Ok, I have made a diagram with the ip addresses I can remember at 1 in the morning.

I have tried configuring the modem and the router both with several combinations of settions. Currently, the router has DHCP turned off, and the Modem has it turned on.

My main concern is that the server "WS1" is able to see the internet, and that the clients "reception" and the Dell laptop can see "WS1".

Let me know if there is any other data we need. I can get the rest of the ip addresses tomorrow if need be.

Thanks!

Chris

Atif Awan · ‎08-18-2010

Have you tried connecting a laptop to the Actiontec using the same physical interface the Linksys connects to? If yes then are you able to get an IP Address via DHCP and access internet. If this works then try connecting this interface to one of the switchports on the Linksys and leave the WAN port out of the picture for the time being. I think this will restore your connectivity and we can work on improving the setup later.

I would be interested to know how you had the linksys configured previously and did you have a DSL Modem/Router like Actiontec previously or was it purely a DSL modem.

chris-sexton · ‎08-18-2010

Hey there-

yes, I have connected the laptop directly (ethernet) to the Actiontec router. I can get internet access.

I have tried then connecting that same cable to a switchport on the Linksys, but I still get no internet access on any of the clients there.

On the linksys, I had DHCP turned on, NAT on, DNS off, UPnP off originally, but over the course of trying to diagnose and correct this issue I have tried pretty much every combination, with no success.

The Actiontec modem/router hasn't changed in nearly a year (old one died and was seamlessly replaced). The new item in the picture is the Netgear router, but none of the clients on that side of the router can see the internet. taking the Netgear router out doesn't change anything.

Thanks again-keep 'em coming. I will try anything!

Chris

Atif Awan · ‎08-18-2010

Hmm ... So if you have DHCP off on linksys and are only using its switchports with Actiontec plugged into one of the switchports itself, any clients connected to the switchport should just be able to get IP Address via DHCP from Actiontec. If this does not work it is time to look deeper and see what the MACs being learnt are (looking at ARP cache on the hosts) and possibly take sniffer captures.

As a starting point I would suggest you disconnect the Netgear for the time being and bring the configuration on devices back to the original working config (NAT/DHCP on Linksys). Next connect the Actiontec cable to Linksys WAN port and verify the WAN port is getting an IP Address from Actiontec. Once this is confirmed connect a laptop to Linksys switchport and verify it gets an IP Address from Linksys. If that works then from this laptop ping the Actiontec IP Address and after this is a success then try browsing for internet. If internet browsing does not work verify DNS. If you are able to make all of this work then Netgear can be introduced back into the equation to see if connectivity remains as desired.

chris-sexton · ‎08-18-2010

Hey-

Ok atawan, thanks. I will give this a try later today. This afternoon the clinic is closed and I can take the network up and down all I want.

I will update with results.

Chris

chris-sexton · ‎08-18-2010

Hey there-

Ok, so I took your advice, disconnected everything, and started with the laptop at the linksys router. Confirmed an IP at the WAN port, confirmed I could ping the router and the gateway, and started adding pieces. 1 at a time, confirming that each piece worked as I added it to the router.

It works!

The weird thing is that I didn't change any settings, and I didn't even reset any equipment as I took apart the network and put it back together. I did log in to each router to confirm settings, but no changes were made.

So, ultimately, I don't know what was wrong! But I documented all the current settings (again), and hopefully we won't have this happen again.

Thanks Atawan!

Atif Awan · ‎08-18-2010

Glad to hear it works. I am just guessing that the issue could have been due to false arp entries but that is just a guess without any evidence :- ). I am just happy that you will no longer be costing additional money to the clinic :- )

Atif