Routing between two different networks for simultaneous internet sharing and LAN connectivity

Discussion in 'Windows Networking' started by Fernando Ronci, Mar 7, 2004.

  1. Hello,

    On a Windows 98 SE host on a LAN, I setup and configured ICS to share its
    modem connection to the internet with other Windows 95 client workstations.
    Also, I installed dhcp_off.inf to disable ICS' own DHCP feature because all
    hosts were assigned static IP addresses. I was able to verify that when DHCP
    is disabled, ICS will work as long as ICS clients have IP addresses from
    class 192.168.0, which is not my case. That is, all my network has been
    assigned addresses from class (I didn't do it in the first place
    and I'm not allowed to change it to 192.168.0). This wouldn't seem to be a
    major problem as it's possible to -easily- add additional IP addresses to
    any given network adapter (as per KB's article 156772) on client
    workstations. This way, in theory, any given client workstation would
    communicate with other peers on the LAN via its, let's say old, IP address
    from class, and at the same time would route its internet traffic
    via its 192.168.0.x address. But this is theory only.
    Well, here is the problem:
    On any given client workstation, its 192.168.0.x IP address is routed
    through gateway, which is the address of the ICS host. This fact
    allows the workstation to access the internet but doesn't allow it to
    communicate with the other hosts on the LAN because, as it can be seen,
    *all* ip traffic (included all packets addressed to 210.1.1.x hosts) gets
    routed through
    The fix for this, so that any given Windows 95 client workstation can access
    the internet and communicate with other workstations *at the same time*
    would be to allow it to route all IP traffic through (this is
    the default setup) except traffic addressed to the local network, which
    shouldn't be routed through the gateway as it must remain on the same
    ethernet segment. I tried some combinations of "route add/change/delete"
    commands on client workstations, but wasn't able to fix the issue, I mean,
    if client workstations have internet access, they cannot see their peers on
    the LAN and viceversa.

    Following are the routing tables on the ICS host and on a typical Windows 95
    client workstation.

    "route print" on the ICS Windows 98 SE host:
    ( is the internal network)

    Active routes:
    Network Address Netmask Gateway Address Interface
    Metric 1 1 2 1 1 1 1 1 2 1 1 1 1 1

    "route print" on the Windows 95 client:
    ( is the ICS host acting as gateway for internet traffic)

    Active routes:
    Network Address Netmask Gateway Address Interface
    Metric 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

    I will highly appreciate hints on how I can fix this, if it is possible.
    Thank you,

    Fernando Ronci
    Fernando Ronci, Mar 7, 2004
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