Advice on network setup 1

[d0nny]

Hi

Not sure this is the right place for this but I felt it was the most suitable given the nature of my query.

I have a small network setup which contains 3, or maybe 4, network devices which 'manage' the comms.
Recently, the ADSL was upgraded and a new BT (this is in the UK) modem was supplied - VDSL modem??. Previously, our ADSL was managed by a Draytek 2820 modem/router. I now need to connect to the new BT modem with the Draytek using the WAN2 port configured as a PPPoE type of connection. That's all fine and works well.
The Draytek has 4 LAN ports on it and I have a server (Ubuntu) on it and a Apple Airport Express plugged into it. The Draytek acts as a DHCP server and assigns IP addresses in the 192.168.0.10-50 range. The Airport assigns IP addresses from 192.168.0.51 up to 50 addresses.
There is also a DELL PowerConnect 2724 switch which is connected to the Draytek 2820. I have not configured this switch at all and I think therein lies my problem, which is this:

If I have a client machine plugged into the Draytek, I get internet access and local LAN access (I can browse the web and also see the server on 192.168.0.10). If I connect that same machine into the DELL switch, I get internet access but I cannot see the local network (I cannot see the local server). If I connect over wi-fi, I get internet access and local network access (I can see the server).

The issue is I don't want client desktops on wi-fi as I have the offices cabled (back the DELL switch). I want to offer wi-fi for iPad's etc.

My thoughts are that I need to do something with the DELL switch as when I connect a client directly into the Draytek, everything is fine, but when I connect to the DELL switch, I do not get local network access. I think it works over the wi-fi as the Airport is directly connected to the Draytek.
As I say, I have not looked at the switch yet to configure it (this was a previous network I inherited so its not a switch out of the box).
I have read that the switch can be in managed or unmanaged mode and I'm not sure what it is setup as right now (I know I can tell from the managed light on the back but I'm not near it right now).
But I suppose I simply want the switch to act dumb and pass on IP addresses as assigned by the Draytek??

Any help appreciated.
D

 

[VinceWhirlwind]

If the PC on the DELL switch can access the internet out the Draytek router, then it would seem everything is fine, connectivity wise...

Plug the PC into the Draytek, then go to the command line and do ipconfig /all
then patch the PC into the DELL and do the same. Compare the two outputs.

The Draytek is acting as your DHCP server in either case, right?

Then, you will need to check the config on the DELL switch. Google for that model switch to find a hardware guide to tell you what console settings you need to console onto it, or even whether it has a web-gui you can access, if it still has its default management IP address on it, or if you can guess or find documented what IP address was assigned to it.
From the switch config, see how the switchports are configured, whether they are all the same, whether there is any sort of filtering etc...

 

[d0nny]

Thanks Vince

I'm going there today to check out the switch. I don't know if it is in Unmanaged or Managed mode so that might give me clues (if it is in Managed mode). UNmanaged it should work out of the box, so the manual says.

 

[d0nny]

OK, got it all working and actually quite easily. By chance? Probably!

I switched the switch into Managed mode and logged into the switch using the default IP address of 192.168.2.1 with the default username of admin and no password.
I set the IP address for a free IP address in my private address range (192.168.0.x) and connected the Draytek. Tested locally (directly connected my laptop and could see all other machines on the local network and also external domains.
I then connected local machines through the switch and was able to see all of the above.

I can only assume the switch was configured in a different way but what confuses me is that switch was in Unmanaged mode??

 

[VinceWhirlwind]

I think some other factor has bamboozled you. Doesn't sound like there was anything wrong with the network.

Perhaps you were trying to use ping to test local connectivity and the host itself was not responding to ping?

But do check there isn't an extra DHCP server running on that network intermittently mucking things up.

 

[VinceWhirlwind]

Two things I often do if I am a bit suspicious are:
1/ Shut down the port that DHCP server is attached to and disconnect/re-connect a client a couple of times to see if any other DHCP is being offered

2/ Ping a device. Disconnect that device. Clear ARP. (If you're pinging a different subnet, clear your router ARP instead)
Ping it again. If it responds, you have a duplicate IP address somewhere!

 

[d0nny]

Well, funny you should mention the DHCP server as I have replaced the Windows Server with Ubuntu Server and I think the Windows machine (which was a domain controller) acted as DHCP server! And its still in the network - not long now before I kill it!

But the network is definitely working much better now since I played with the switch. Maybe just rebooting it to get it to a default state sorted it?