2 ISP's

Hi,

I have 2 broadband providers, I have a couple of network storage devices attached to broadband provider 1's router - I want to be able to access them when I am hooked onto broadband provider 2. I can physically connect the two routers, what reconfig would I need to do to effectively be able to see both networks when logged into either ISP?

It's a bit of a faff but you can set up both routers to be on the same LAN IP address range but with different IP addresses and plug their LANs into a switch. You disable DHCP on one of the routers and then use a manual IP address on your client devices that you want to be able to change between different ISPs. You do this by changing the default router and DNS servers from ISP 1 to ISP 2 as desired.

A far simpler way is to get a separate multi-wan router and use that to manage both ISP connections.

This will work and a multi-wan capable router is still the best approach.

However if the OP already has 2 Wi-Fi routers and wants to do something with what they have,
there is another method, but preferably if both routers support:
- creating a second distinct LAN network as a L3 link
- creating static routes

Setup each router's main LAN with different IP subnets.

R1-LAN = 192.168.10.1/24
R2-LAN = 192.168.20.1/24

Setup a different SSID on each router's Wi-Fi.

Setup each router's secondary LAN without DHCP as a point-to-point network link:
(Note this generally requires that you can assign individual physical ports to the secondary LAN.)

R1-LAN2 = 192.168.0.1/30
R2-LAN2 = 192.168.0.2/30
(if your routers won't let you specify this type of minimal network size you can use a /24 instead but be consistent on both.)
You need to patch the routers together using the port on each assigned to this secondary LAN.

On each router setup a static route for the neighbour's main LAN.

on R1, 192.168.20.0/24 via next hop 192.168.0.2
on R2, 192.168.10.0/24 via next hop 192.168.0.1

Now by switching wired connection between either router's regular LAN port or by switching between Wi-Fi networks, one can select either ISP, but the other LAN will be reachable via the L3 link.

This is more complex than a single multi-wan router, and in any case its a good idea to make sure you can resolve the storage devices by their private DNS name on the LAN. Too many setups rely on discovery broadcast or multicast which without hacks (such as multicast repeaters or proxies) only works on the same network/subnet.

However it does mean you don't need to apply manual computer or phone settings to set and change which gateway, as you can continue to let the network auto-configure them by DHCP.

Text
1 23 45 67 8	....{ISP-1}...............{ISP-2}......          │                     │      ┌────┐      LAN2      ┌────┐       │ R1 │────────────────│ R2 │      └────┘{192.168.0.0/30}└────┘          │                     │      LAN│                     │LAN {192.168.10.1/24}     {192.168.20.1/24}

Edited by prlzx (Sun 10-Jan-21 13:06:32)

In reply to a post by prlzx:

On each router setup a static route for the neighbour's main LAN.

The reason I didn't suggest this approach is that most ISP supplied routers and many other home market routers simply don't have the ability to set up a static route or multiple subnets. That might be a limitation here.

Edited by caffn8me (Sun 10-Jan-21 14:46:43)