Network trouble with multiple Routers

By mephisto_007 ยท 15 replies
Mar 29, 2007
  1. Guyz I am having some real issue right now, after introducing a new Wireless Router for the conference the current network suddenly gone bad (Internet running slow, and won't work in some case - but if I disconnect/unplug the new Wireless Router everything is back in business)

    Here is my network infrastructure.


    The weird things is I got very good signal from New Wireless Router and able to ping most sites but having problem with browser won't loading the page. Also old network tense to lose it connectivity sometime able to use the net and some other time it won't and like I had mention before if I disconnect the new Wireless Router everything back to normal. The real question is, what did I do wrong please help me
  2. jobeard

    jobeard TS Ambassador Posts: 11,168   +986

    With that topology (wiring), I would make sure both wireless routers were
    at the opposing ends of the channels; one on channel-1, the other on channel-11.

    Set different SSIDs

    Make sure ALL routers have the latest firmware
    and ALL systems do too. It often makes a difference.

    How many systems are on the downlink side of the HUB? You might find
    better thruput and more reliability by using a switch.

    Hey! Just noticed that the new wireless is attached to the modem-- what gives,
    Don't tell me one is via rj45 and the other is USB; this doesn't work!
    Move # 2 router to a lan port on router #1,
    wireless#1(lan) --->wireless#2(lan) not the WAN!
    make it an Access Point and disable DHCP on #2
  3. mephisto_007

    mephisto_007 TS Guru Topic Starter Posts: 228


    There are quite afew systems on network #1, more than 10 systems connected diasy chain hub by hub, (4 hubs is using on network #1) I am not sure but people told me that newer HUB nowaday is like a switch or perhap what must I say to them if I ask for a switch and instead they gave me a Hub and said they're the same?, that happened to me with my last Hub's purchased.

    Both wireless routers is attached to the modem (via RJ45, no USB) so they both have different network (I don't want wireless client on wireless #2 to access network #1, not sure if this is correct)

    I'm just wondering could it be the IP address that I have assign to the router? or is it correct?
  4. jobeard

    jobeard TS Ambassador Posts: 11,168   +986

    sorry, they are quite different! There's a lot of traffic on Ethernet
    and a hub just duplicates it all to every port attach. A switch will forward traffic
    ONLY to the proper port for the system that needs it. That's 9/10% savings
    for your ten downstream systems:)

    The are different by virtue of the addresses, not the physical wiring layout.

    When it all works correctly, you control access from net-1 to net-2 via the
    firewall on all systems
    (yes you need a set of new rules for each client)

    I think you can make the new router into an Access Point and cause to to
    dish out different addresses or a split address range ...

    Nodsu, Comments?
  5. Samstoned

    Samstoned TechSpot Paladin Posts: 1,018

    thats what you need to make it function downstream make it a switch or (access point)
    disable dhcp in wirreless router
    give it a sub net ip of say mask
    these numbers based on router ip of
  6. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    Hum.. So the modem is a router device too? (It apparently has an IP address and several LAN ports). Should I say yet again, that you should have used (a) wireless access point(s) instead of (a) router(s)? :p

    It would help if you posted the exact IP configuration of the modem and both plain routers. This includes WAN and LAN side IP addresses (or "automatic"), netmasks (or "automatic") and gateways (or "automatic").
  7. mephisto_007

    mephisto_007 TS Guru Topic Starter Posts: 228

    You're correct, the modem is also a wireless router device so can it's be an issue?

    Below are their IP address



    Wireless Router (#1)

    Wireless Router (#2 new installed)
    Has the same configuration as Router #1 except its IP address is

    I'm looking forward for a solution from you guyz.

    I have another question, what is the maximum of HUB can be used in a network which connected through a router without much noise/interfer etc etc?
  8. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6


    The modem is in bridge mode, so it's not acting as a router at the moment.

    The two routers ought to have different WAN IP addresses. If they both have, then that is most certainly an issue. Give the other one for example. Of course, you have to tell your ISP that you want to use two IP addresses.

    If you have only one public IP, then you could configure the modem as a router and have it share this one public IP to the two wireless routers.

    The LAN side IPs of the wireless routers are pretty much irrelevant..
  9. jobeard

    jobeard TS Ambassador Posts: 11,168   +986

    >what is the maximum of HUB can be used in a network which connected
    >through a router without much noise/interfer etc etc?

    that's known as a capacity planning issue. the hub per se is not the problem,
    but rather how much traffic can a single subnet carry without major degradation?

    Ethernet is a contention network by design, meaning any output is written to
    the NIC w/o concern Is it already busy? This results in a real thruput of about
    70% of the rated NIC card, eg a 10mb card can carry 7mb without going into
    error recovery, a 100mb runs at 70mb.

    This is an advantage for the switch; it only forwards to the specific system,
    allowing all others attached to see nothing of that flow. If we assume
    10 systems on a switch, all ten can run 70mb at the same time without error
    recovery, while a hub will choke due to the 700mb attempt on a 10mb nic;
    in fact, the hub will choke with just two systems attempting 70mb each.

    So, whenever you fan-out the wiring with nested devices, always favor
    switch -- switch -- switch
  10. mephisto_007

    mephisto_007 TS Guru Topic Starter Posts: 228

    I just called my ISP and they have informed me that they're only provided us with only 1 WAN IP address and if we wants them to come and reconfigure the modem there will be an extra charge plus they wouldn't let me peak at what they did. So could you guide me step by step on how to reconfigure the modem to handle the other router?
    ie: if the modem act as a router will its Local IP address be and the other 2 router Local IP, and so on? will the 1st router still be able to communicate with the 2nd router?
  11. mephisto_007

    mephisto_007 TS Guru Topic Starter Posts: 228


    Thank alot that's really informative...
  12. jobeard

    jobeard TS Ambassador Posts: 11,168   +986

    This is typical, so don't go crazy on this.
    A router has a NAT feature that will solve your problem. The ISP connection
    will always be a single address, but NAT will allow your systems to piggyback
    it and get replies (like you're already doing). You only need to keep the
    new systems segregate from the old.

    you already have
    modem( other wired systems
                                                      + ----- other wireless systems
    your desire for the second router is to segregate a third group of systems (not shown)
    from the existing ones. I assume you may want file/print sharing(FS) on the
    new systems and to prohibit access from the existing -- there is a way --
    control the firewalls on the new systems.

    1. inventory the MAC addresses of all systems (new + old)
    2. make static addresses for all existing systems (eg: addresses > using their MACs)
    3. make static addresses for all new systems (eg: addresses starting from using their MACs)
    4. get a good firewall (aka Comodo) for all NEW systems
    5. config all New Systems + Comodo to control FS
      (eg allow tcp/udp source ip ports 137,139,445)

    and btw; you can swap any hub for a switch and anytime without changing
    any other configuration :)
    1 person likes this.
  13. mephisto_007

    mephisto_007 TS Guru Topic Starter Posts: 228

    modem( other wired systems
    + ----- other wireless systems

    Hi, by looking at the diagram which router should the NAT be apply (I have nerver done NAT before) I pressume the MODEM is still untouch (as bridge), ROUTER #1 is configured with NAT and ROUTER #2 is attached to ROUTER #1 through LAN port? please correct me if I'm wrong...
  14. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    OK. Ignoring all of the above (you guys seem to be talking about different things)..

    You can stack either 4 or 2 levels of hubs. The total number is irrelevant. So make sure that between any client and the router, there are no more than 2 or 4 hubs.

    I don't have access to your modem, so I have no clue about what configuration options you have available.

    Now, you want the people on the second network not to be able to access the first one. This means that we have to daisy-chain the routers so that they all are doing NAT.

    Things would look like this:
    (we ignore the modem IP, since it's irrelevant to the network setup and used only for managament)

    Connect the router that is hosting the restricted clients (router2) to the modem using the WAN port. Set the WAN IP to your public IP address. Set the LAN IP range to whatever you like.
    Connect the router that is hosting the trusted users (router1) to the lan port of router2. Configure the WAN interface of router1 to either obtain IP configuration automatically or statically to fit the LAN configuration of router2. Configure the LAN side of router1 to have an IP range different from the LAN side of router2.

    You would have: modem--router2--router1--hubs

    (This is a very ugly setup!)

    If you figure out a way to configure your modem to act as a router, then you can connect your network like you had in mind or even optimise a bit more, connecting the LAN side of router2 to the modem (and disabling DHCP).
  15. mephisto_007

    mephisto_007 TS Guru Topic Starter Posts: 228

    I've got both router to work now, thank you guyz so much for this... :)

    By the way here is how I did it, Modem still untouch (as bridge) ---> Router #1 (WAN = ISP provided, LAN 192.x.x.2) -----> Router #2 attached to Router #1 through LAN port (WAN = 192.x.x.3, LAN 10.x.x.x) now it worked :)
  16. jobeard

    jobeard TS Ambassador Posts: 11,168   +986

    Very good! With your modem in bridge mode, you can ONLY have one device
    (ie router) directly attached. Everything else will be on the LAN side of that router.

    As for 'access from one side or the other', if one of the OLD systems can ping
    any of the new systems, then the firewalls on the new will need to block the old.
    If they can not ping, then both sides are hidden and inaccessible to the other :)
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