Solved: Network settings help

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drwinny

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I have an issue with two routers on one network both having DHCP servers running one can be switched off but when it is the customer says some devices no longer receive IP addresses

Please see the attached network diagram for more information.

Summery of the setup:

DHCP server 1:

IP range: 192.168.2.1 – 192.168.2.252

DHCP server 2:

IP range: 192.168.0.100 – 192.168.0.200

Both using a subnet mask of: 255.255.255.0


I have given the following information:

These are two different IP address ranges, which could be causing the communication issue with the printer.

For a class C IP address (with your subnet mask) you can use the following settings:

Start host address: 192.168.0.1
End host address: 192.168.0.254
Max number of hosts: 254

Using a subnet mask of: 255.255.255.0

You also have your DHCP lease set for two days, which is possibly why everything works for a few days and then you start getting issues.

I have suggested:

Turning one of the DHCP servers off and just use the one, devices connected to the second router should still receive an IP address from the DHCP server on the other router.

This will stop the different IP address ranges conflicting with each other and everything should be able to communicate properly.

The other option is to change the subnet mask on all devices to: 255.255.254.0

This would give you the following IP range:

Start host address: 192.168.0.1
End host address: 192.168.1.254
Max number of hosts: 510

Using a subnet mask of: 255.255.254.0

This method would allow you to keep both DHCP servers running without causing any problems.

My question:

Is the information that I have given correct?
Could anyone offer a different solution?

Thanks,

drwinny
 

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Triple6

Rob
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Why are you running two routers in the first place? Using a switch and if necessary an access point would be the proper way. Running two DHCP servers on the same network without VLANs is not a good idea.
 

drwinny

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I work for a printer company and this is a customers setup. He is reviewing one of our products.

I dont want to tell him how to run his network as such just want a way around the issue.

If the best way is to dump the one router and just use a wi-fi extender or something i will just say that
 

drwinny

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I do understand that his setup is not correct, i was just looking for a work around so he could use his setup without getting more equipment
 

TerryNet

Terry
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In the diagram I cannot tell for sure for either router whether the ethernet cable between the routers plugs in to the WAN or a LAN port.

These are two different IP address ranges, which could be causing the communication issue with the printer.
What is the communication issue?
 

drwinny

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I need to check with him but I would guess its a LAN port connection, the communication issue is with his wireless printer he uses the software to setup the wi-fi on the printer and configure the printer ports. Everything works for a couple of days and the it stops printing. My guess was that because he has two different DHCP servers on his routers that after the dhcp lease expires maybe some of his equipment switches from a 192.168.0.1 range to a 192.168.2.1 range stopping it working.
 

drwinny

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that is possible, but the software uses the mac address not the IP address.

am I correct in saying that If one device had an IP address of 192.168.0.2 and the other device had 192.168.2.3 and both had subnet masks of 255.255.255.0 they would not be able to communicate with each other?

But if the subnet mask changed to 255.255.254. on all devices then communication would be possible?
 

TerryNet

Terry
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am I correct in saying that If one device had an IP address of 192.168.0.2 and the other device had 192.168.2.3 and both had subnet masks of 255.255.255.0 they would not be able to communicate with each other?
You are correct.

But if the subnet mask changed to 255.255.254. on all devices then communication would be possible?
Yes, but.... I think you need 255.255.252.0. And both routers have to handle that; I think--don't know this--that not all routers can handle a mask other than 255.255.255.x.
 

Triple6

Rob
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If you have two routers you will have two networks unless you disable DHCP on the second router and use it as a switch only. That's the easiest solution without replacing hardware or doing significant changes.

You can actually have stuff on the second router talk to the stuff on the first router if you use the WAN port on the second router but stuff on the first router will be unaware of stuff on the second router unless you setup routes and I'm not sure that would work.

If you leave both DHCP servers running then and use the WAN port on the second router to connect to the first then changing the subnet still won't work, the first router still won't be able to see the stuff behind the second router. If you use the LAN port on the second router to uplink to the first router then you will have DHCP pointlessly running twice on the same network and causing conflicts and possibly the whole network may crash.

A dynamic IP address on the printer is also generally a bad idea, give it a static IP address if it doesn't already have one.

However if its a business they should just get a switch and an wireless access point to replace that second router.

Actually, what is the purpose of the Floor 1 router? There isn't just one PC connected to it is there? If so why not just directly connect the cable going to the router to the computer instead? Also is it connected by wireless to the first router so that it can print? Technically that setup should work, even though its unnecessarily complicated, unless the computer is switching wireless networks to the second router or the printer is indeed switching IP's and the computer is having trouble resolving the name if its not setup by IP address.
 

drwinny

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Hi All,

Thanks for your help with this, I understood that the customers setup was incorrect and would cause him problems.

I will check with him why he uses the router on the second floor, I would think it is just something simple like having a better wireless signal.

I will check and see if he has a WAN port on the router and the other suggestions given.

I wanted to makes sure that other people agreed that his network setup would cause problems before asking him to change equipment.

Thanks again for the clarification and help with this.

drwiiny
 

TerryNet

Terry
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If the customer needs a second wireless access point (which is likely) the following is not the best solution for a business but is a good solution given that they already have the equipment.

JohnWill's procedure (Aug. 30, 2008) for configuring a secondary router as a switch and, optionally, wireless access point follows.

Connecting two (or more) SOHO broadband routers together.

Note: The "primary" router can be an actual router, a software gateway like Microsoft Internet Connection Sharing, or a server connection that has the capability to supply more than one IP address using DHCP server capability. No changes are made to the primary "router" configuration.

Configure the IP address of the secondary router(s) to be in the same subnet as the primary router, but out of the range of the DHCP server in the primary router. For instance DHCP server addresses 192.168.0.2 through 192.168.0.100, I'd assign the secondary router 192.168.0.254 as it's IP address, 192.168.0.253 for another router, etc.

Note: Do this first, as you will have to reboot the computer to connect to the router again for the remaining changes.

Disable the DHCP server in the secondary router.

Setup the wireless section just the way you would if it was the primary router, channels, encryption, etc.

Connect from the primary router's LAN port to one of the LAN ports on the secondary router. If there is no uplink port and neither of the routers have auto-sensing ports, use a cross-over cable. [You will not need a cross-over cable if one of the "routers" is a computer.] Leave the WAN port unconnected! [TerryNet Note: assume that all routers made in the last five or six years or more have auto-sensing ports.]

This procedure bypasses the routing function (NAT layer) and configures the router as a switch (or wireless access point for wireless routers).
 

drwinny

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7
Thank you for the answer, I will try this with the customer and see if that works.

Thanks again for your help
 
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