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-   -   Routers and DSL (https://www.askmehelpdesk.com/showthread.php?t=160305)

  • Dec 6, 2007, 07:16 PM
    KISS
    My default gateway is 10.0.1.1 at home. It's still a private address. DHCP addresses are low numbers (2 computers and a radio) with yearly leases and the fixed IP addresses for printers are high numbers. I can't get to my DSL modem because I am operating in Bridge mode.

    If anybody can explain the relationship of Router (Default gateway IP address) and the IP address of a DSL modem modem operating in Bridge mode, I'd be gratefull. I never did try to set the IP address of the modem in the same network, say 10.0.1.30 and see if I could reach it. It currently has a 192.168.x.y address and works just fine. I just have to connect directly to it when my PC is set to a fixed address in 192.168.x.y.

    {moved to one thread-<>}
  • Dec 7, 2007, 07:51 AM
    retsoksirhc
    Quote:
    Originally Posted by KeepItSimpleStupid
    My default gateway is 10.0.1.1 at home. It's still a private address. DHCP addresses are low numbers (2 computers and a radio) with yearly leases and the fixed IP addresses for printers are high numbers. I can't get to my DSL modem because I am operating in Bridge mode.

    If anybody can explain the relationship of Router (Default gateway IP address) and the IP address of a DSL modem modem operating in Bridge mode, I'd be gratefull. I never did try to set the IP address of the modem in the same network, say 10.0.1.30 and see if I could reach it. It currently has a 192.168.x.y address and works just fine. I just have to connect directly to it when my PC is set to a fixed address in 192.168.x.y.
    When we set up DSL modems for our clients, we put them in bridged mode, and they take on the IP address of the default gateway. So, if there was an IP range of 4.2.2.1-4.2.2.6, depending on the decumentation from the ISP, set the modem to bridge mode and give it an IP of 4.2.2.1 or 4.2.2.6, then set the WAN port on the firewall to a static of 4.2.2.2 or anything else unused in that range.

    Router mode is basically the modem doing NAT for you and giving you a local IP. It routes packets BETWEEN the two networks. Bridge mode means your modem is just passing the info TO the network, rather than translating between two addresses.
  • Dec 7, 2007, 08:32 AM
    KISS
    Quote:
    Originally Posted by retsoksirhc
    Wehn we set up DSL modems for our clients, we put them in bridged mode, and they take on the IP address of the default gateway. So, if there was an IP range of 4.2.2.1-4.2.2.6, depending on the decumentation from the ISP, set the modem to bridge mode and give it an IP of 4.2.2.1 or 4.2.2.6, then set the WAN port on the firewall to a static of 4.2.2.2 or anything else unused in that range.
    That doesn't seem to make sense. My default gateway is my router ip address and my MODEM in bridged mode isn't even assigned an IP address in my network. You can't have two addresses assigned to the same unit. So, the statement of the "DSL modem taking on an address of the default gateway" has to be wrong.

    Now, it might be possible with a creative use of the subnet mask of the router, to pass packets to the DSL modem. As I undersatnd it, packets shouldn't reach the WAN port of the router with a subnet mask DG/router IP: 10.0.1.1 with SM of 255.255.255.0. If they don't reach the WAN port, they can't get to the DSL modem. Right?
  • Dec 7, 2007, 08:44 AM
    retsoksirhc
    Quote:
    Originally Posted by KeepItSimpleStupid
    That doesn't seem to make sense. My default gateway is my router ip address and my MODEM in bridged mode isn't even assigned an IP address in my network. You can't have two addresses assigned to the same unit. So, the statement of the "DSL modem taking on an address of the default gateway" has to be wrong.

    Now, it might be possible with a creative use of the subnet mask of the router, to pass packets to the DSL modem. As I undersatnd it, packets shouldn't reach the WAN port of the router with a subnet mask DG/router IP: 10.0.1.1 with SM of 255.255.255.0. If they don't reach the WAN port, they can't get to the DSL modem. Right?
    The DSL modem doesn't actually take the IP from anything that's currently connected... it takes on the ROLE of the default gateway for the other devices connected to the LAN side of the modem. So, if we set the modem to 4.2.2.1, then we could set the firewall's WAN port to 4.2.2.2, with a SN mask of /29, and a GW of 4.2.2.1.
  • Dec 7, 2007, 08:46 AM
    retsoksirhc
    Actually this link may help a bit... I got a copy of it the first time I set this up, as we were using the same modem.
    Netopia -- Bridge Mode

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