SOS - two NICs installed on a PC do not work at the same time

This is a very strange issue. We install two NICs on a PC (Linux or
Windows), and use two crossover Ethernet cables to connect each NIC to a
different Ethernet port on an iSCSI router.

NIC 1 (IP 192.168.100.200) connects to port 1 (IP 192.168.100.121) of iSCSI
router.
NIC 2 (IP 192.168.100.201) connects to port 2 (IP 192.168.100.123) of iSCSI
router.

From the PC, we can ping 192.168.100.123, but not 192.168.100.121. If we
disconnect the cable to 192.168.100.123, then we can ping 192.168.100.121.
Both NIC use the same configuration but different IPs.

I would appreciate it if some one can give me a hint why we can not ping
192.168.100.121.

Thanks,


T.
--

On Mon, 8 Nov 2004 19:30:08 -0600, L <(E-Mail Removed)> wrote:
> This is a very strange issue. We install two NICs on a PC (Linux or
> Windows), and use two crossover Ethernet cables to connect each NIC to a
> different Ethernet port on an iSCSI router.
>
> NIC 1 (IP 192.168.100.200) connects to port 1 (IP 192.168.100.121) of iSCSI
> router.
> NIC 2 (IP 192.168.100.201) connects to port 2 (IP 192.168.100.123) of iSCSI
> router.
>
> From the PC, we can ping 192.168.100.123, but not 192.168.100.121. If we
> disconnect the cable to 192.168.100.123, then we can ping 192.168.100.121.
> Both NIC use the same configuration but different IPs.
>
> I would appreciate it if some one can give me a hint why we can not ping
> 192.168.100.121.

Check your routing table in both cases (/sbin/route -n). With 2
interfaces using same network/netmask, you have duplicate conflicting
routes, so only the first matching route in routing table will be used.
If you want to have more than 1 interface using the same network/netmask,
you should read Adv-Routing HOWTO.

I do not know what an iSCSI router is, but I imagine it may also have a
routing conflict unless it has "host" routes instead of "network" routes
to your IPs.

"L" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...

> This is a very strange issue. We install two NICs on a PC (Linux or
> Windows), and use two crossover Ethernet cables to connect each NIC to a
> different Ethernet port on an iSCSI router.
>
> NIC 1 (IP 192.168.100.200) connects to port 1 (IP 192.168.100.121) of
> iSCSI
> router.
> NIC 2 (IP 192.168.100.201) connects to port 2 (IP 192.168.100.123) of
> iSCSI
> router.
>
> From the PC, we can ping 192.168.100.123, but not 192.168.100.121. If we
> disconnect the cable to 192.168.100.123, then we can ping 192.168.100.121.
> Both NIC use the same configuration but different IPs.
>
> I would appreciate it if some one can give me a hint why we can not ping
> 192.168.100.121.

What's the subnet mask?

DS

Agreed, this won't work. You should have each interface on a seperate subnet
(assuming /24 network)

"David Efflandt" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Mon, 8 Nov 2004 19:30:08 -0600, L <(E-Mail Removed)> wrote:
> > This is a very strange issue. We install two NICs on a PC (Linux or
> > Windows), and use two crossover Ethernet cables to connect each NIC to a
> > different Ethernet port on an iSCSI router.
> >
> > NIC 1 (IP 192.168.100.200) connects to port 1 (IP 192.168.100.121) of
iSCSI
> > router.
> > NIC 2 (IP 192.168.100.201) connects to port 2 (IP 192.168.100.123) of
iSCSI
> > router.
> >
> > From the PC, we can ping 192.168.100.123, but not 192.168.100.121. If
we
> > disconnect the cable to 192.168.100.123, then we can ping
192.168.100.121.
> > Both NIC use the same configuration but different IPs.
> >
> > I would appreciate it if some one can give me a hint why we can not ping
> > 192.168.100.121.
>
> Check your routing table in both cases (/sbin/route -n). With 2
> interfaces using same network/netmask, you have duplicate conflicting
> routes, so only the first matching route in routing table will be used.
> If you want to have more than 1 interface using the same network/netmask,
> you should read Adv-Routing HOWTO.
>
> I do not know what an iSCSI router is, but I imagine it may also have a
> routing conflict unless it has "host" routes instead of "network" routes
> to your IPs.

"David Schwartz" <(E-Mail Removed)> wrote in message
news:cmpim4$plu$(E-Mail Removed)...
>
> "L" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>
> > This is a very strange issue. We install two NICs on a PC (Linux or
> > Windows), and use two crossover Ethernet cables to connect each NIC to a
> > different Ethernet port on an iSCSI router.
> >
> > NIC 1 (IP 192.168.100.200) connects to port 1 (IP 192.168.100.121) of
> > iSCSI
> > router.
> > NIC 2 (IP 192.168.100.201) connects to port 2 (IP 192.168.100.123) of
> > iSCSI
> > router.
> >
> > From the PC, we can ping 192.168.100.123, but not 192.168.100.121. If
we
> > disconnect the cable to 192.168.100.123, then we can ping
192.168.100.121.
> > Both NIC use the same configuration but different IPs.
> >
> > I would appreciate it if some one can give me a hint why we can not ping
> > 192.168.100.121.
>
> What's the subnet mask?

255.255.255.0