Default Route question when there are two nic cards
David G. Miller
dave at davenjudy.org
Thu Oct 12 03:04:57 UTC 2006
Jeff Vian <jvian10 at charter.net> wrote:
>If your system is acting as a gateway router for other systems on your
>local network there are different issues involving static routes. For a
>workstation on 2 different networks, only one default gateway can be
>used.
>
This system is also my router. eth0 (as per the annotations) has my
public IP address and is my gateway to my ISP. eth1 is the gateway for
systems on my LAN. That is, all of the systems on my LAN show a routing
table that looks something like:
[dave at bend ~]# netstat -n -r
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt
Iface
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0
eth1
192.168.0.0 0.0.0.0 255.255.0.0 U 0 0 0
eth1
0.0.0.0 192.168.255.254 0.0.0.0 UG 0 0 0
eth1
I point people in this direction because their next question is usually,
"How do I get the "other system" onto the internet?" Also, only one
default gateway ends up defined in the routing table. The system does
the right thing and uses the the default gateway specified for eth0 even
though the gateway specified by eth1 comes "later:"
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt
Iface
72.19.169.0 0.0.0.0 255.255.255.0 U 0 0 0
eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0
eth1
192.168.0.0 0.0.0.0 255.255.0.0 U 0 0 0
eth1
0.0.0.0 72.19.169.1 0.0.0.0 UG 0 0 0
eth0
Cheers,
Dave
--
Politics, n. Strife of interests masquerading as a contest of principles.
-- Ambrose Bierce
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