Thread: Gateways

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    Gateways


    Hi.

    We are using Windows Server 2003 SBS with the standard DNS server untouched from the initial installation, and have an ADSL router with everything going into one switch and all PCs connect via it.

    All the PCs use DHCP with the Scope Options setting the Router to be the IP address of the ADSL router.

    All very standard.

    However, we also have a separate fibre optic internet connection that was installed to handle a bespoke, browser based management system and this goes through a separate router, also connected via the same switch as everything else.

    The problem is that as far as each PC is concerned, there is only one gateway - the ADSL router set via DHCP - so the fibre optic internet never gets used by the bespoke system.

    So, we have two routers, both connected to the internet, with different LAN side IP addresses, but on the same subnet. The question is how do we get the browser based management system to use one router and everything else to use the other?

    If it sounds like I don't understand DNS properly, then it's probably because I don't, so please bear with me.

    One obvious question is why not use the fibre for everything but without going into it all, we can't. The other obvious option is to have any PC using the bespoke system set up to not use DHCP and to set the Default Gateway as the second router. However without going into it, this is not the preferred option.
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    This does not sound like a DNS issue, but rather a network issue. You could combine the two gateways using a higher end router. I believe All Cisco routers are capable of connection sharing.

    Without understanding your situation completely, let me try to explain networks. Each subnet is defined by an address and a netmask. For example 10.0.0.5/255.255.255.0 defines a network of 254 addresses starting with 10.0.0.1 and ending with 10.0.0.254. 10.0.0.255 is the broadcast address for the subnet 10.0.0.0. Each subnet has a single designated gateway residing on the same subnet (LAN) as well as a wider network (WAN). When a destination address is selected, the netmask is applied to that address, and if it is on the same network the packet is routed locally. Otherwise it is routed to the gateway. This of course is for IPv4 networks, as IPv6 networks are somewhat different.

    J.A. Coutts
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    Hi. Thanks for the reply. Taking one point:
    Originally Posted by couttsj
    ..Each subnet has a single designated gateway residing on the same subnet...
    This is as I have always understood it. So, any non-local traffic is directed at the "default gateway" for routing on and in this context, having more than one gateway on the same subnet for outgoing traffic would be a nonsense.

    Maybe our situation is more easily explained in this way. Suppose a company gave us a router and said "At the other end of this is our bespoke web server through which you access our web based system. However, it can only be accessed this way, and not through the normal internet, nor can you use it for anything other than our system, but you are able to give it any LAN side ip address you want.".

    Would it be possible to have a PC access the internet via one router and the other bespoke web site via another?

    I know this sounds like a slightly mad situation but this is effectively the reality.

    Tim
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    You could add a route to the route table on each PC using the Route command and make it persistent. I had one government network that would not supply Internet service. So I added a second router and added a persistent route to provide Internet service. The government network still provided DNS service.

    J.A. Coutts
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    Originally Posted by couttsj
    You could add a route to the route table on each PC using the Route command and make it persistent. I had one government network that would not supply Internet service. So I added a second router and added a persistent route to provide Internet service. The government network still provided DNS service.

    J.A. Coutts
    Great idea. To be honest, I have never used the route command but it looks like it might do exactly what is needed. Thank for the help.

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