Router and server network addresses

Posted on 2009-12-18
Last Modified: 2012-05-08
We have a SBS 2003 and a Watchguard Firebox. These were installed and configured several years ago.

Is there any reason why the Watchguard was set up with an internal IP of, the server is addressed A few printers and switches with static IPs and the other 25 or so PCs with DHCP addresses from the server.
The 2 switches are and 2 (I would have thought the router would have been
The scope is - 151.

I ask this because we are installing a new router (DrayTek) on a new broadband line.
Would it be best for me to address the router as and then change the switch from to Or is there a reason I should know about for this numbering scheme?

Thanks for your time.
Question by:NELMO
    LVL 3

    Expert Comment

    I would install the router on  I have no idea why that firebox would be its own ip block.  Sounds like a routing nightmare to me.
    LVL 21

    Expert Comment

    The only thing I can think of is that maybe there is another VLAN and subnet on the switch and the Firebox is in that range?
    LVL 1

    Accepted Solution

    If the server address is and the Firebox address is, and the server is able to get traffic through the firewall, then I'm guessing you are on a class B subnet (subnet mask  This means that there is no problem with the addresses you have in place now.  It seems the admin before you just chose to have switches, servers, and workstations together in the 172.16.0.x range, while firewalls and routers are in the 172.16.1.x range.  Other than personal preference, it really doesn't matter what range you put these devices in, since they all appear to be in the same broadcast domain.

    All that being said, if you are bringing in a router with broadband on the other end, that should be on the "other side" of your firewall, rather than next to it.  I happen to manage a few WatchGuard Firebox 1250e firewalls in my network if you need advice about how to configure a multi-wan environment.
    LVL 8

    Expert Comment

    Have you checked that the SBS is in a single NIC configuration?  What is the default gateway on the clients set to?

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