Solved Can't access Internet and local server simultaneously after router change

princeofpersia

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Hello all. I'm currently trying to solve a problem with our office network as per diagram below. Our ISP tech support was not very helpful - "anything involving servers and switches are not our expertise", so I hope someone here will be able to help shed some light!

Untitled.png


This arrangement was previously OK for both Internet and local server connectivity. However, we recently had to change our router. With the new router, this arrangement no longer works - PCs can still access the server but not the Internet. No Internet whether via cable or WiFi (although devices are able to connect to the WiFi signal without issue).

The new router is working fine - if a PC is connected directly to it rather than via the switch, the PC is able to get Internet access.

All PCs use automatic IP and DNS addresses for IPv4. I read somewhere and thus also tried putting 1.1.1.1 and 1.0.0.1 as the preferred/alternate DNS addresses but that did not solve the problem.

I also logged in to the new router's default gateway at 192.168.0.1 and tried copying all the details e.g. IP address, subnet mask, default gateway into the IPv4 settings. Again this did not work.

In the advanced TCP/IP settings for IPv4, I also tried adding a DNS suffix (which for us is companyname.local), as well as toggling (all permutations) the checkboxes (1) append parent suffixes of the primary DNS suffix, (2) register this connection's addresses in DNS, and (3) use this connection's DNS suffix in DNS registration. None of these worked.

The 24-port switch has 3 DIP switches, one of which is for "port isolation/storm control". This switch has always been off and remained so as per my descriptions above. I then tried to experiment with this switch as I read from the quick install guide that when enabled, "Ports 1 to 23 will be isolated from each other, but will still be able to communicate with port 24. Port 24 will be able to communicate with all the other ports."

DIP switch disabled
server into any port + router into any port - access to server OK, no Internet access

DIP switch enabled
Experiment 1 - server into port 24 - access to server OK, no Internet access
Experiment 2 - router into port 24 - Internet access OK (both cable and WiFi), no server access

I then thought, what if I can get both the server and router signals input into port 24. I found 2-port LAN splitters, but all of them have a manual switch i.e. only 1 of the 2 input signals is active at any time, via push of either button A or B. So then I tried:

Experiment 3 - both server and router into a 5-port switch, with a third LAN cable connecting one of the 5 ports into port 24 of the main switch - no server access, no Internet access

Therefore, my hypothesis is there is conflict between the server and new router signals. I've put links below to the datasheets for both old/new routers, plus the switch, modem and server. Reading through all of them, particularly comparing the two routers, I was unable to pinpoint anything that may have caused any issues. Searching online, I also could not find cases of incompatibility between router/switch or router/server (of any brands/models).

Product datasheets:
D-Link DGS-1024D switch - link
Netis DL4480V1 router (old) - link
D-Link DVG-F2452 router (new) - link
Huawei HG8240H modem - link
Dell PowerEdge T410 server - link

For those wondering why we can't just change the router - we're stuck under contract with this ISP for another 2 years and the new router is their latest (and only) model that they currently supply. So the time/money/effort I spend on troubleshooting this (which I personally do enjoy) is likely less than the penalty of changing ISPs.

Please let me know if I need to provide any further details. Thank you all for your time and assistance.
 
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Try3

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You're sure that the old router was not connected to the server rather than the switch?

Denis
 

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princeofpersia

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You're sure that the old router was not connected to the server rather than the switch?

Denis
Yes, 100% sure. We still have the old router so we swapped it in to test and everything works as it should. The old router (10 years old!) is of a lower bandwidth hence we got a new one from our ISP, but we're surviving on it for now.
 

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johngalt

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Is the new router configured with the same DHCP settings as the old router?

Also, when I go to D-Link Technical Support it asks for a hardware revision before accessing any guides. However, only HW REv G has a Datasheet matching.

It also has this for the Quick Install guide:


In reading that, on page 5, it shows that default switch positions are OFF / ON / OFF, and that when changing switch positions you need to power cycle the switch.

Also, the only time you need to actually use port 24 for access, it seems, is if you use DIP 2 set to ON, otherwise your current setup looks perfectly fine in the picture.

But with your detailed experiments (Thank you, BTW!) something is clearly not correct.

For the HW Rev D, for example, which does have a full User Manual linked, it says much the same thing:

2. Does the DGS-1016D/1024D switch have an uplink port?

The DGS-1016D/1024D has Auto-MDI ports which automatically sense the type of cable being used (e.g. straight-through or Crossover) and adjust themselves accordingly to pass data over the network.

But it also says this, which you've shown is what you're already doing, and which works with your old router:

1. Why can´t I share my Internet connection to multiple computers when using my D-Link DGS-1016D/1024D switch?

If you are connecting directly to a Cable or DSL modem, you will need a router to “share” your Internet connection or a computer using ICS (Internet Connection Sharing) or Proxy. Switches and hubs do not allow you to share a single IP address to multiple computers.

Another alternative is to contact your ISP and purchase extra IP addresses for each additional computer.

That user manual has some troubleshooting steps for networking at the end, which leads me to ask a few questions:

After replacing the router, and setting it up, did you clear all the DNS entries in all the PCs?

See this tutorial from our sister site TenForums (10F):


So, set everything up exactly as you have it in your picture, and resetting the DIP switches on the switch back to default as noted above and power cycling it, then one by one, starting with the server, do this (step 1 or step 2, whichever you prefer) and see if they start seeing each other and maintain their Internet connectivity.

Finally, if everything but Internet works, try moving the router to port 24 and leaving everything else as it is and see if machines can now see the router and the internet.

Also, are the PCs set up with static IP addresses or using DHCP to get the address from the gateway? I believe DHCP, simply because your DIP switch experiment showed multiple PCs getting Internet access when the router was plugged into port 24 and Isolation was enabled, but there may be more to it. We may need to inspect the settings of each PC's networking individually (including the server) to get them all working correctly with the new router, which is why I'm hoping the DNS flush works.

Good luck!
 

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bython

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Since you say that the wifi works, could you confirm that it is the wifi signal that is send out by the router or are there accesspoints?

If by the router then I would like to know which network settings those devices via wifi receive. Is it in the same range, etc.?

Can you confirm which is your DHCP server, is it your server or is it the router?

If it is the server, did you check if the new router has DHCP disabled?
Since you say that connecting a pc directly to the router works, I am quite certain DHCP is on, and if the server is also a DHCP server that can become an issue.
 

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princeofpersia

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I finally found some time yesterday to continue my efforts. It's a bit difficult now as with Covid restrictions easing, I can only troubleshoot outside of office hours.

Thank you @johngalt, for it is this quote below from your reply that sparked my a-ha moment:
then one by one, starting with the server

All this while I had been fiddling with the settings for the router, switch, work PCs, etc. - completely forgetting to check the settings for the server! This revealed that the IPv4 of the server was pointed towards a specific IP address 192.168.1.225 with preferred/alternate DNS servers 8.8.8.8 and 8.8.4.4

I reverted both of these to auto, then did a full system reset - putting the DIPs on the switch back to defaults and power cycling it, followed by ipconfig /flushdns for all PCs including the server, then restarting those PCs. Yay - we now have Internet and local server connectivity! (I am most definitely curious as to why connectivity was not affected when using the old router)

Then I discovered that our accounting software (AS) couldn't work. The error received was "Unable to complete network request to host '192.168.1.255'. Failed to establish a connection." I then realised what had happened - the previous person (an external contractor) must have pointed the server to 192.168.1.225 in order to match the existing IP setting of the AS, when it should have been the other way round! (the AS database is located on the server) I changed the IP of the AS to match the new IP of the server and voila, now the AS works.

AND THEN I discovered that we've lost connectivity to our printer. *big sigh* Symptoms as follows:

1. Switch does not show active signal from printer (port LED off)
- tried different ports and LAN cables to ensure that it's not a hardware issue

2. PCs unable to detect printer
- power cycled the printer after the aforementioned network reset, and it auto-acquired a new IP address
- tried un/re-installing latest version of printer driver; printer not automatically detected during installation and manual input of new IP also didn't work
- AirPrint on my boss' iPhone also no longer able to detect the printer

3. Printer network settings
- if I change the printer to be connected via wireless instead of wired LAN, everything works fine (PCs on the same wireless network are able to detect the printer), however most of our computers are unable to connect via wireless so this is not a solution
- as it was late in the day, I did not have time to fully explore all of the settings; I will find some time this week to do so as I probably missed something

The printer is a Canon MF628Cw
(1) The 'Getting Started' manual can be found here
(2) The full manual is available as a web version here
(3) The full manual makes references to the 'MF Driver Installation Guide', which can be found here

Any advice/suggestions would be most welcome with much gratitude!
 

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princeofpersia

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So I found some time again today to continue my troubleshooting and finally managed to solve the problem. For this particular printer (and perhaps other Canon models too), after adjusting all the necesary network settings and the printer acquiring a new IP after power cycling, it was not enough.

In the network settings menu, the last item is "Initialize Network Settings". I selected this, and then "Yes" from a yes/no choice to proceed. Then the printer required another power cycle. After this, everything was back to normal! Even the AirPrint connection to my boss' iPhone was restored.

We also just realised that our CCTV system also went offline after the router change, but that was easily resolved by power cycling each individual camera. Is it the case that replacing a router would necessitate an entire network to require a reset? Anyway, all good now and I'll mark this thread as solved. Thanks again to all who read!
 

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johngalt

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Glad you got it all worked out!
 

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