Question Two Seperate Networks having Problems

Mar 28, 2022
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I have set up two networks at my house with two separate routers, one for personal, one for business. There is one modem, but my ISP provides me with two WAN addresses. The modem is also in bridge mode, so the built in router is not being used. The modem address is 10.0.0.1, my home network using Unifi equipment is 192.168.1.1 and my office network is the Araknis router at 192.168.0.1.

My problem is that devices from one network will jump to the other network when they reboot. I would say my networking skills are intermediate, but I can’t understand why this keeps happening. Both networks will seem solid for a few weeks or longer, then one day my wife cannot connect to the NAS on the home network because her computer jumped over to my business network.

Both networks are set up the exact same: Cat6 out of the modem to the WAN port of the router, LAN port connected to a gigabit switch, access points connected to the switch. I get full speed on both networks (300Mbps) when they are set up. When I am connected to each network via WiFi, I can confirm each one is on the right network using ipconfig. I have also confirmed each network is getting a separate WAN network by looking backwards using whatsmyip.com.

When devices get rebooted, why do they bypass the router they are connected to and grab an address from the other router? Is there any hardware way to isolate them further? Thanks for any help.
 

kanewolf

Titan
Moderator
I have set up two networks at my house with two separate routers, one for personal, one for business. There is one modem, but my ISP provides me with two WAN addresses. The modem is also in bridge mode, so the built in router is not being used. The modem address is 10.0.0.1, my home network using Unifi equipment is 192.168.1.1 and my office network is the Araknis router at 192.168.0.1.

My problem is that devices from one network will jump to the other network when they reboot. I would say my networking skills are intermediate, but I can’t understand why this keeps happening. Both networks will seem solid for a few weeks or longer, then one day my wife cannot connect to the NAS on the home network because her computer jumped over to my business network.

Both networks are set up the exact same: Cat6 out of the modem to the WAN port of the router, LAN port connected to a gigabit switch, access points connected to the switch. I get full speed on both networks (300Mbps) when they are set up. When I am connected to each network via WiFi, I can confirm each one is on the right network using ipconfig. I have also confirmed each network is getting a separate WAN network by looking backwards using whatsmyip.com.

When devices get rebooted, why do they bypass the router they are connected to and grab an address from the other router? Is there any hardware way to isolate them further? Thanks for any help.
Are both routers connected to a common switch? If so you have two DHCP servers visible. It is then random as to which DHCP responds to a request.
 
Mar 28, 2022
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Are both routers connected to a common switch? If so you have two DHCP servers visible. It is then random as to which DHCP responds to a request.
Thanks for responding. No, both routers are connected to thier own switch. I have lots of networking equipment. The only connection point of both networks is the modem to the WAN port of each router. After that, they are both physically isolated.
 
Mar 28, 2022
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If these "jumping" devices are connecting over WiFi - simply delete WiFi profile for the "wrong" router, or configure that connection not to auto reconnect.
Some of the devices that are jumping are WiFi, but some of them are hardwired, which makes no sense. My last resort is to put as many devices as I can on static IP address so they will stay in thier designated networks. I prefer to keep everything on DHCP however. I will report back if I make any progress.
 
Mar 28, 2022
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So after a bunch of testing, I have concluded that certain devices will gravitate to grabbing an address from one DHCP server over the other. Even though both routers I have are getting thier own WAN address, they are essentially on the same network. Because both routers are on the same network, I have no way to force a device when it connects to which DHCP server it grabs an address from other than giving it a static IP address. I thought forsure that if a device connected to one router, then it would automatically get its address from that routers DHCP server, but nope.
 
Mar 28, 2022
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Are both routers connected to a common switch? If so you have two DHCP servers visible. It is then random as to which DHCP responds to a request.
I am changing my answer to your previous question. There are two ports on the back of the modem where both routers are connected to. So, yes they are connected to the same switch. And you are right, it is random which DHCP server responds to a request. I was not able to influence this without assigning static IP address to devices.
 

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