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Re: Wan/Lan problem




On Tue, Mar 28, 2017 at 04:46:02PM -0700, Mike McClain wrote:
> Howdy,
> I have a WAN/LAN challenge I'm hoping for help with.
> 
> I'm runniing Debian 7.11 on a Pentium 3 with 250MB ram.
> 
> mike@/deb7:~> uname -a
> Linux playground 3.2.0-4-686-pae #1 SMP Debian 3.2.84-2 i686 GNU/Linux
> 
> 
> The situation is this:
> 
>      phone        eth0         eth1
> AT&T-------|   |--------|   |--------|   |-------|   |
>         AT&T modem/     Linux         my         Win2K
>             router       box         router       box
> 
> When eth0 is up and eth1 down,
>                     the Linux box can access the web.
>                     'ping ATTrouter' works.
> When eth0 is up and eth1 up,
>                     the Linux box can not access the web.
>                     the Win2K box can access the web.
>                     the Linux box can not access the Win2K shares.
>                     'ping ATTrouter' fails.
>                     'ping -Ieth0 ATTrouter' works.
> When eth0 is down and eth1 up,
>                     the Linux box can access the Win2K shares.
> When eth0 is down and eth1 down,
>                     it's quiet.
> 
> The ATT router is set to 'Pass Through' giving the Linux box the ATT
> router's IP address.
> The Linux box is set to use DHCP.
> This might explain why I loose the LAN connection when eth0 up.
> 
> Why can the Linux box not see the web while the Win2K box can?
> 
> I've not found or at least recognized the problem in the HowTo's.
> Pointer's or suggestions?
> 
> Thanks,
> Mike
> 
> 
> # The loopback network interface
> auto lo
> iface lo inet loopback
> 
> # The primary network interface
> allow-hotplug eth1
> #   eth0 = onboard eth port
> iface eth0 inet dhcp
> #   eth1 = 3Com PCI 3c905C card
> iface eth1 inet static
>         address 192.168.1.2
>         netmask 255.255.255.0
>         network 192.168.1.0
>         broadcast 192.168.1.255
>         # dns-* options are implemented by the resolvconf package, if installed
>         dns-nameservers 208.67.222.222 208.67.220.220

You're going to end up discovering that this is a problem in IP
assignment, routing, forwarding, or something very similar.

What masquerading are you doing? What IP forwarding? What
routing entries are present?

-dsr-