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How to connect two routers on the same network

By jobeard · 18 replies
Jan 16, 2017
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  1. Start with your existing network:
    • ISP==modem==router#1 (may or may not have wifi)
    You wish to add a second router (perhaps with wifi) like
    • ISP==modem==router#1 ----- router#2
    There are two ways to use router#2
    1. isolate all devices on #2 from those on #1 (ie no file sharing)
    2. make all devices visible to each other & support file sharing

    To implement #1;
    first, find the router#1 LAN address
    use IPCONFIG and the gateway address shown is the router's address
    we usually see something like 192.168.X.1

    Then, set the router#2 Lan address to X+1, like 192.168.2.1
    connect any LAN port on #1 to the WAN slot on #2 and you're done.

    All devices on router#2 will be able to access the Internet, but nothing on the internet will have access to router#2 and that means if you are hosting some service of game on your system, it will need to be connected to router#1

    To implement #2:

    You need to disable DHCP in router#2 to allow all addresses to be
    controlled by router#1

    connect a pc to any router lan slot
    login the router using your browser and the router's default address
    use the default user/password
    find the router settings
    disable DHCP
    save & logout

    Now disconnect the PC and connect router#1 lan slot to any
    router#2 lan slot, leaving router#2 WAN slot empty

    any device on router#1 will be able to ping the devices on router#2 and conversely.

    WiFi Considerations
    One tool that is really helpful with WiFi is inSSIDer. This helps
    finding a channel with the least conflicts in your location.

    Router#1 (if it has wifi) should be solved first

    When you add router#2, you can make the SSID similar to that of #1,
    but add a suffix '2' so you can tell them apart.

    *IMPORTANT*
    Make sure that when both routers have WiFi, that they are NOT using
    the same channels! Otherwise, you're interfering with yourself.
     
    Stupido, Julio Franco, misor and 4 others like this.
  2. learninmypc

    learninmypc TS Evangelist Posts: 8,709   +569

    Thank you & I appreciate your knowledge. :)
     
  3. Bigtruckseries

    Bigtruckseries TS Evangelist Posts: 583   +322

    I recently added 2 switches to my home FIOS network. WiFi is ok for the smartphones and tablets, but I like keeping my game systems, streaming systems and NAS servers wired.

    Some devices have a specific "uplink" port which you connect the data cable from the 1st router into. The new device may be able to configure itself once it recognizes the uplink port is in use.
     
    stewi0001 likes this.
  4. Evernessince

    Evernessince TS Evangelist Posts: 3,657   +2,976

    Nice article, simple and to the point. You'd be surprised how few articles there are on this specific setup that is becoming very common as people with ISP router / modem combo's are adding their own router to the network.
     
  5. learninmypc

    learninmypc TS Evangelist Posts: 8,709   +569

    My landlord is the one that originally told me to do this a few years back. Not being able to afford a router then, I asked friends & managed to get one. Now when I clean a friends pc, I can put it on wifi & leave mine on ethernet. :)
     
  6. jobeard

    jobeard TS Ambassador Topic Starter Posts: 12,668   +1,476

    Yes, but that requires the use of UPnP on the system AND in the router also. As UPnP is a know intrusion vector, I disable it on my home router and on my PC as well. Anything that needs UPnP assistance can be manually configured with the application setup instructions and if the port requirements are not fully disclosed, then you're asking for problems.

    Case #2 above allows router #2 to operate as a switch and/or an access point. Any server programs need only
    1. the correct portforward in the router
    2. and a fixed ip address via address reservation configured in router#1
    It also fully supports all wired and wifi connections.
     
  7. jobeard

    jobeard TS Ambassador Topic Starter Posts: 12,668   +1,476

    :grin: Oh Yeah! I have a friend who has changed ISPs multiple times and the transition is just unplug the personal router from the OLD ISP modem and connect to the NEW ISP modem - - no changes necessary whatsoever :grin:
     
  8. Kurt Tomicich

    Kurt Tomicich TS Rookie

    Have set up both types many, many times as a consultant. Recently had a low-end Cisco router, acting as an edge router for the network, that would spontaneously reboot when either of these configurations were present on the network. No explanation for it.
     
  9. jobeard

    jobeard TS Ambassador Topic Starter Posts: 12,668   +1,476

    Sounds like it needs a firmware update.
    In Config#1 the edge router will see an extra DHCP request and could get 'excited' about that and mishandle the request.
    Config #2 doesn't do this as it is acting as a transparent switch (aka does not present it's IP anywhere), so the downstream devices from #2 just flow-thru to #1 normally.

    Amazingly strange as Cisco is the enterprise level kind of device, whereas Linksys, Netgear, ..., are consumer devices but handle both of these well :sigh:
     
  10. Kurt Tomicich

    Kurt Tomicich TS Rookie

    Config 1 doesn't expose the Cisco to Router2's DHCP server and in Config 2 DHCP is turned off. Additionally, I typically set Router2 with a static LAN address outside of Router1's DHCP scope.
    This was a super small Cisco, still supposedly "professional grade," provided by a VOIP vendor and, supposedly, it had it's latest firmware.
    It was super weird - I've done this, literally, hundreds of times with cheap-*** routers. Never had one act like this Cisco did.
     
  11. hkhan1989

    hkhan1989 TS Enthusiast Posts: 31   +24

    In the past whenever I have done this, (for various reasons), I tend to go a slightly different route.
    Router 1 - Becomes a Modem
    Router 2 - Becomes the primary router

    Connect Router 1 to Router 2's WAN port and configure a static IP
    e.g.
    Router 1 would be 192.168.0.1 Router 2 would be 192.168.0.2.
    Router 1 to have DMZ on 192.168.0.2
    DHCP enabled on Router 2 - all devices connect to Router 2 on a different range - router IP / gateway of this network would be 192.168.1.1).

    From the above we can go two routes.
    1. Configure router 1 to be locked down (no wifi, no DHCP), strictly acting as a modem (for devices that do not allow the router function to be changed into a modem only mode)
    2. Configure router 1 to be kept on a different range, like 192.168.0.x, with DHCP range starting after Router 2's static IP, e.g. DHCP range 192.168.0.3 upwards.

    The 1st route allows you to use say your ISP's router alongside your own one, in a situation where you HAVE to use the ISP's crappy router (much like UK's Relish Broadband Service).

    The 2nd route allows you to maintain effectively two networks, all going down the same broadband line.
    I have set this in the past for a few friends who run a little business at home, using their home broadband, creating two effective networks allows the user to use his Router 1 for his family, and Router 2 for work, with Work shared servers / printers never on the same network.
    No devices on Router 2 can connect to devices on Router 1
    Devices on Router 1 have a way to connect to devices on Router 2 - but we don't care about that!
     
  12. Phr3d

    Phr3d TS Guru Posts: 404   +86

    At the risk of sounding as untalented as I am - would you consider an article like this one to address TWO ISP's incoming and the need for local shares across both routers? I have read what little I've been able to find, and bought the ASUS as it was supposed to be able to handle exactly that, but I've never managed to get the two local LANs (created by Two routers on different ISPs, I.e., cable and DSL) to be visible to each other.

    No doubt my description is clear as mud.. I tried.
     
  13. jobeard

    jobeard TS Ambassador Topic Starter Posts: 12,668   +1,476

    The first issue is DUAL HOMING. Then connection the two routers via Persistent Routes - - both are a totally different subject
     
  14. hkhan1989

    hkhan1989 TS Enthusiast Posts: 31   +24

    Well if you want to have two routers with two different WANs, that would mean there would be two Gateways.

    To have two different gateways on the same IP range, only one router can be a DHCP server. Whatever you want connected to the other router, will have to be on a static IP with the gateway manually pointing to the secondary router.
    Anything you want to share across both routers have to be via IP and not hostnames, unless you want to manually put entries on each devices hosts files.

    If you want me to elaborate, just let me know.
     
  15. Phr3d

    Phr3d TS Guru Posts: 404   +86

    Just to make sure I am following, the two incoming feeds are for fail-over, presently we simply throw a manual switch if DSL ever goes down (work 24/7) and use cable.
    It sounds like you are saying there is no way to offer the LANs (work and local) to appear to each other in our use?
     
  16. hkhan1989

    hkhan1989 TS Enthusiast Posts: 31   +24

    If it's for failover, then you only need one router which supports failover.

    Check here
    https://leonid.shevtsov.me/post/how-to-configure-dual-wan-on-asuswrt-routers/
     
    Phr3d likes this.
  17. Phr3d

    Phr3d TS Guru Posts: 404   +86

    Thanks, my head is already swimming, lol. Thought it was just my google skills typically lacking, but this seems to be why I could not find a "how to" (I mistakenly believed that the ASUS router would do what I had in mind).
     
  18. jobeard

    jobeard TS Ambassador Topic Starter Posts: 12,668   +1,476

    Raise this as a separate subject --we're getting way off the subject.
     
    Phr3d likes this.
  19. Phr3d

    Phr3d TS Guru Posts: 404   +86

    Agreed (with better understanding).
    apologies and thanks!
     

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