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Tip: using multiple routers

By jobeard
Jan 15, 2007
  1. Usually, the home user has little need for two or more routers.
    To get more connectivity, one only needs to add a switch/hub
    (switch is preferred) to the existing router and more slots become
    available for more systems.

    The typical case for the home user to add a router is expanding a wired
    LAN and adding wireless connectivity at the same time. The issue will
    be the configurability of both routers. The setup will look like

    modem -- routerA ---- routerB ---b-systems
               +------ a-systems
    Which router is existing vs new really doesn't matter other than getting
    the configuration correct. If I had my choice however, the B-router
    would be my new wireless router for security reasons (later described).
    A wireless Access Point would also fit nicely in the router-B location.


    Both routers will need to be configured, likely hardwired at first to
    one of your systems. You will need to access your router’s
    configuration page which is brand-name dependent:


    Once you've logged into the router, be sure to set a new admin password!

    TWO parameters will determine success/failure of the configuration:
    (1) the router's ip-address and (2) the subnet mask.
    (of course you need the other stuff too, but these determine the data flow)

    The typical problem that can arise is the inability to set the subnet
    mask to a value that will work -- some vendors get parochial and force
    some assumption that cause problems (sorry, no I don't have a list).

    Here's what needs to be created:
    Router-A ip-address must be higher numerically than router-B,
    eg: 192.168.X.1 versus 192.168.Y.1 where X > Y

    Secondly, the subnet mask for router-A must allow traffic to flow down
    to router-B. A typical subnet mask for home users would be but this would allow traffic ONLY for the router-A,
    where the b]X[/b] value was an exact match (thus dropping traffic for
    router-B). What we need is a subnet mask more like
    (your X value will then be 2 thru 7)

    Your vendor may not let you set a value like 252 in the third
    position, or if it does, it might get reset when you save the

    If this occurs to you, you can try an alternative class-b addresses like
    172.16.X.1 vs 172.16.Y.1​
    These addresses require a different subnet mask and the parochial rules
    need to be dropped -- give it try at least.

    You also might try swapping the devices and
    trying the steps above again. If that doesn't work either, you're just SOL
    -- S*** out of luck; punt and return the last device purchased.

    Each router can still auto config its devices using DHCP.

    Be sure to save the configuration, AND restart the router.

    Router-B needs only to meet the rule where X > Y
    and may use the typical subnet mask

    With at least one system hardwired to each router,
    you should now be able to
    a) ping your ISP from all systems
    b) ping from a-system to b-system and conversely
    when this works correctly, the routers are ready for general use and the
    wireless setup can be configured for channel, ssid, and wap/wep

    Whichever router has the wireless enabled should be considered your
    untrusted subnet and have the firewalls configured to not allow
    print/file sharing. You can implement this on each system's firewall OR
    use that router's port forwarding feature to protect all system;
    just forward ports 139,445 to a non-existing system :)

    If you really need print/file sharing, then by all means
    1) force your devices to known IP addresses by mapping the MAC addresses of the NIC adaptor, and
    2) keep a consecutive ip address set for your systems,
    3) allow print/file sharing ONLY for this narrow range of address in your firewalls

    In this case obviously, you can't use the port forwarding trick above.

    In addition, your wireless router will have an SSID and allow WAP/WEP
    encryption features. You really should implement WAP or at least WEP.
  2. nuetres

    nuetres TS Rookie

    how to setup wireless router to wireless router
    please give me some help
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