Two internet connections via two modems, one router, specify which modem to use on PC

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At work, we have two internet connections via two modems, one cable modem and one 4G modem. To the cable modem, there is a WiFi router connected, that is our network A. The 4G modem has a built-in WiFi router, that is our network B. Some of the computers use network A, some use network B.

Now the problem: On network A there is a network printer that we would like to access also from the PCs on network B. My plan now is to connect router A and router B with a cable, disable DHCP on router B and give it a static IP address.

How is it possible to specify for each computer which internet connection to use?

edited 50 mins ago

GabrielaGarcia

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asked 2 hours ago

eliman20000

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How is it possible to specify for each computer which internet connection to use?

edited 50 mins ago

GabrielaGarcia

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asked 2 hours ago

eliman20000

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How is it possible to specify for each computer which internet connection to use?

edited 50 mins ago

GabrielaGarcia

561215

asked 2 hours ago

eliman20000

New contributor

How is it possible to specify for each computer which internet connection to use?

networking wireless-networking router internet modem

edited 50 mins ago

GabrielaGarcia

561215

asked 2 hours ago

eliman20000

New contributor

edited 50 mins ago

GabrielaGarcia

561215

asked 2 hours ago

eliman20000

New contributor

edited 50 mins ago

GabrielaGarcia

561215

edited 50 mins ago

GabrielaGarcia

561215

edited 50 mins ago

GabrielaGarcia

561215

asked 2 hours ago

eliman20000

New contributor

asked 2 hours ago

eliman20000

asked 2 hours ago

eliman20000

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eliman20000 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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3 Answers
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active

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votes

up vote
2
down vote

You can run a single network with two DHCP servers by assigning the same network prefix but different ranges of IP addresses. For example:

Router 1:

Network address: 172.25.60.0
LAN interface: 172.25.60.1
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.61.0 - 172.25.61.255

Router 2:

Network address: 172.25.60.0
LAN interface: 172.25.60.2
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.62.0 - 172.25.62.255

The tricky part then is to ensure that each device get a DHCP response from the intended router such that they will use the intended gateway. By default they will simply use whichever is fastest to respond. And since you appear to have a different access point connected to each router, that might just work as expected - most of the time.

That's not quite satisfying. If the routers allow you to specify a whitelist/blacklist of MAC addresses to which they assign addresses you can use that to control which device gets to use which gateway. That will have the device use the same gateway regardless of which of the access points it connects to.

Alternatively you can disable DHCP on both routers and use a separate device to act as DHCP server. On that separate device you can install a much more flexible DHCP server. Any Linux machine with ISC dhcpd would work.

A completely different approach is to configure one of the routers as IPv4-only and the other as IPv6-only. That will allow all devices to use both routers depending on what's supported by the services they are communicating with. (This requires at least one of the ISPs to support IPv4 and at least one to support IPv6.)

answered 1 hour ago

kasperd

2,43711125

1

I'm upvoting this because it seems to be the only response attempting to actually answer the question.
â€“Â Tim_Stewart
1 hour ago

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Setup a USB printer server - A lot, but not every router has this built in - It would also need to be wireless so it can attach to the 4G wifi network. Something like the TL-WN822N - WLAN USB Adapter.

Wifi print server

Now, assuming that your printer is attached to the other network via ethernet, the USB port should still work. The printer will now accept requests from the main network and the wireless 4g network.

answered 2 hours ago

JohnnyVegas

2,2221714

I'm upvoting this because even though it doesn't technically answer the question as written it provides an alternative approach to solve the requirement which motivated the question. Depending on the hardware used and specific needs this may or may not be a better solution than the plan to achieve the goal through changes in network topology.
â€“Â kasperd
19 mins ago

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up vote
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You can make it one network if you cable it as LAN-to-LAN and not LAN-to-WAN :

With this setup, you only need one connection to the internet through
the cable modem. The 4G modem will become a WiFi access point extending
the network created by the cable modem, and should have its DHCP server
disabled.

For more information, see this answer.

edited 4 mins ago

answered 2 hours ago

harrymc

242k10254537

It sounds like the goal is to still use both internet connections. This answer doesn't achieve that. Moreover this answer is short on detail about how the secondary router is configured.
â€“Â kasperd
1 hour ago

The "missing" details are already in the post. The only missing piece is the cabling.
â€“Â harrymc
1 hour ago

And how do you then configure which computer use which ISP?
â€“Â kasperd
1 hour ago

1

The question says: "we have two internet connections via two modems, one cable modem and one 4G modem"
â€“Â kasperd
1 hour ago

1

This is an inappropriate answer. If you believe it's a duplicate, flag it as such linking it to the other question. but this in no way attempts to answer the question.
â€“Â Tim_Stewart
57 mins ago

Â |Â
show 5 more comments

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3 Answers
3

active

oldest

votes

3 Answers
3

active

oldest

votes

up vote
2
down vote

You can run a single network with two DHCP servers by assigning the same network prefix but different ranges of IP addresses. For example:

Router 1:

Network address: 172.25.60.0
LAN interface: 172.25.60.1
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.61.0 - 172.25.61.255

Router 2:

Network address: 172.25.60.0
LAN interface: 172.25.60.2
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.62.0 - 172.25.62.255

answered 1 hour ago

kasperd

2,43711125

1

I'm upvoting this because it seems to be the only response attempting to actually answer the question.
â€“Â Tim_Stewart
1 hour ago

add a commentÂ |Â

up vote
2
down vote

You can run a single network with two DHCP servers by assigning the same network prefix but different ranges of IP addresses. For example:

Router 1:

Network address: 172.25.60.0
LAN interface: 172.25.60.1
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.61.0 - 172.25.61.255

Router 2:

Network address: 172.25.60.0
LAN interface: 172.25.60.2
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.62.0 - 172.25.62.255

answered 1 hour ago

kasperd

2,43711125

1

I'm upvoting this because it seems to be the only response attempting to actually answer the question.
â€“Â Tim_Stewart
1 hour ago

add a commentÂ |Â

up vote
2
down vote

You can run a single network with two DHCP servers by assigning the same network prefix but different ranges of IP addresses. For example:

Router 1:

Network address: 172.25.60.0
LAN interface: 172.25.60.1
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.61.0 - 172.25.61.255

Router 2:

Network address: 172.25.60.0
LAN interface: 172.25.60.2
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.62.0 - 172.25.62.255

answered 1 hour ago

kasperd

2,43711125

You can run a single network with two DHCP servers by assigning the same network prefix but different ranges of IP addresses. For example:

Router 1:

Network address: 172.25.60.0
LAN interface: 172.25.60.1
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.61.0 - 172.25.61.255

Router 2:

Network address: 172.25.60.0
LAN interface: 172.25.60.2
Netmask: 255.255.252.0
Broadcast: 172.25.63.255
DHCP range: 172.25.62.0 - 172.25.62.255

answered 1 hour ago

kasperd

2,43711125

answered 1 hour ago

kasperd

2,43711125

answered 1 hour ago

kasperd

2,43711125

answered 1 hour ago

kasperd

2,43711125

1

I'm upvoting this because it seems to be the only response attempting to actually answer the question.
â€“Â Tim_Stewart
1 hour ago

add a commentÂ |Â

1

I'm upvoting this because it seems to be the only response attempting to actually answer the question.
â€“Â Tim_Stewart
1 hour ago

I'm upvoting this because it seems to be the only response attempting to actually answer the question.
â€“Â Tim_Stewart
1 hour ago

add a commentÂ |Â

up vote
1
down vote

Wifi print server

Now, assuming that your printer is attached to the other network via ethernet, the USB port should still work. The printer will now accept requests from the main network and the wireless 4g network.

answered 2 hours ago

JohnnyVegas

2,2221714

I'm upvoting this because even though it doesn't technically answer the question as written it provides an alternative approach to solve the requirement which motivated the question. Depending on the hardware used and specific needs this may or may not be a better solution than the plan to achieve the goal through changes in network topology.
â€“Â kasperd
19 mins ago

add a commentÂ |Â

up vote
1
down vote

Wifi print server

Now, assuming that your printer is attached to the other network via ethernet, the USB port should still work. The printer will now accept requests from the main network and the wireless 4g network.

answered 2 hours ago

JohnnyVegas

2,2221714

I'm upvoting this because even though it doesn't technically answer the question as written it provides an alternative approach to solve the requirement which motivated the question. Depending on the hardware used and specific needs this may or may not be a better solution than the plan to achieve the goal through changes in network topology.
â€“Â kasperd
19 mins ago

add a commentÂ |Â

up vote
1
down vote

Wifi print server

Now, assuming that your printer is attached to the other network via ethernet, the USB port should still work. The printer will now accept requests from the main network and the wireless 4g network.

answered 2 hours ago

JohnnyVegas

2,2221714

Wifi print server

Now, assuming that your printer is attached to the other network via ethernet, the USB port should still work. The printer will now accept requests from the main network and the wireless 4g network.

answered 2 hours ago

JohnnyVegas

2,2221714

answered 2 hours ago

JohnnyVegas

2,2221714

answered 2 hours ago

JohnnyVegas

2,2221714

answered 2 hours ago

JohnnyVegas

2,2221714

I'm upvoting this because even though it doesn't technically answer the question as written it provides an alternative approach to solve the requirement which motivated the question. Depending on the hardware used and specific needs this may or may not be a better solution than the plan to achieve the goal through changes in network topology.
â€“Â kasperd
19 mins ago

add a commentÂ |Â

I'm upvoting this because even though it doesn't technically answer the question as written it provides an alternative approach to solve the requirement which motivated the question. Depending on the hardware used and specific needs this may or may not be a better solution than the plan to achieve the goal through changes in network topology.
â€“Â kasperd
19 mins ago

I'm upvoting this because even though it doesn't technically answer the question as written it provides an alternative approach to solve the requirement which motivated the question. Depending on the hardware used and specific needs this may or may not be a better solution than the plan to achieve the goal through changes in network topology.
â€“Â kasperd
19 mins ago

add a commentÂ |Â

up vote
0
down vote

You can make it one network if you cable it as LAN-to-LAN and not LAN-to-WAN :

For more information, see this answer.

edited 4 mins ago

answered 2 hours ago

harrymc

242k10254537

It sounds like the goal is to still use both internet connections. This answer doesn't achieve that. Moreover this answer is short on detail about how the secondary router is configured.
â€“Â kasperd
1 hour ago

The "missing" details are already in the post. The only missing piece is the cabling.
â€“Â harrymc
1 hour ago

And how do you then configure which computer use which ISP?
â€“Â kasperd
1 hour ago

1

The question says: "we have two internet connections via two modems, one cable modem and one 4G modem"
â€“Â kasperd
1 hour ago

1

This is an inappropriate answer. If you believe it's a duplicate, flag it as such linking it to the other question. but this in no way attempts to answer the question.
â€“Â Tim_Stewart
57 mins ago

Â |Â
show 5 more comments

up vote
0
down vote

You can make it one network if you cable it as LAN-to-LAN and not LAN-to-WAN :

For more information, see this answer.

edited 4 mins ago

answered 2 hours ago

harrymc

242k10254537

It sounds like the goal is to still use both internet connections. This answer doesn't achieve that. Moreover this answer is short on detail about how the secondary router is configured.
â€“Â kasperd
1 hour ago

The "missing" details are already in the post. The only missing piece is the cabling.
â€“Â harrymc
1 hour ago

And how do you then configure which computer use which ISP?
â€“Â kasperd
1 hour ago

1

The question says: "we have two internet connections via two modems, one cable modem and one 4G modem"
â€“Â kasperd
1 hour ago

1

This is an inappropriate answer. If you believe it's a duplicate, flag it as such linking it to the other question. but this in no way attempts to answer the question.
â€“Â Tim_Stewart
57 mins ago

Â |Â
show 5 more comments

up vote
0
down vote

You can make it one network if you cable it as LAN-to-LAN and not LAN-to-WAN :

For more information, see this answer.

edited 4 mins ago

answered 2 hours ago

harrymc

242k10254537

You can make it one network if you cable it as LAN-to-LAN and not LAN-to-WAN :

For more information, see this answer.

edited 4 mins ago

answered 2 hours ago

harrymc

242k10254537

edited 4 mins ago

answered 2 hours ago

harrymc

242k10254537

answered 2 hours ago

harrymc

242k10254537

answered 2 hours ago

harrymc

242k10254537

It sounds like the goal is to still use both internet connections. This answer doesn't achieve that. Moreover this answer is short on detail about how the secondary router is configured.
â€“Â kasperd
1 hour ago

The "missing" details are already in the post. The only missing piece is the cabling.
â€“Â harrymc
1 hour ago

And how do you then configure which computer use which ISP?
â€“Â kasperd
1 hour ago

1

The question says: "we have two internet connections via two modems, one cable modem and one 4G modem"
â€“Â kasperd
1 hour ago

1

This is an inappropriate answer. If you believe it's a duplicate, flag it as such linking it to the other question. but this in no way attempts to answer the question.
â€“Â Tim_Stewart
57 mins ago

Â |Â
show 5 more comments

It sounds like the goal is to still use both internet connections. This answer doesn't achieve that. Moreover this answer is short on detail about how the secondary router is configured.
â€“Â kasperd
1 hour ago

The "missing" details are already in the post. The only missing piece is the cabling.
â€“Â harrymc
1 hour ago

And how do you then configure which computer use which ISP?
â€“Â kasperd
1 hour ago

1

The question says: "we have two internet connections via two modems, one cable modem and one 4G modem"
â€“Â kasperd
1 hour ago

1

This is an inappropriate answer. If you believe it's a duplicate, flag it as such linking it to the other question. but this in no way attempts to answer the question.
â€“Â Tim_Stewart
57 mins ago

It sounds like the goal is to still use both internet connections. This answer doesn't achieve that. Moreover this answer is short on detail about how the secondary router is configured.
â€“Â kasperd
1 hour ago

The "missing" details are already in the post. The only missing piece is the cabling.
â€“Â harrymc
1 hour ago

And how do you then configure which computer use which ISP?
â€“Â kasperd
1 hour ago

The question says: "we have two internet connections via two modems, one cable modem and one 4G modem"
â€“Â kasperd
1 hour ago

This is an inappropriate answer. If you believe it's a duplicate, flag it as such linking it to the other question. but this in no way attempts to answer the question.
â€“Â Tim_Stewart
57 mins ago

Â |Â
show 5 more comments

eliman20000 is a new contributor. Be nice, and check out our Code of Conduct.

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