 |
Linux Format forums
Help, discussion, magazine feedback and more
|
| View previous topic :: View next topic |
| Author |
Message |
sproot
Joined: Mon Aug 13, 2007 9:55 pm
Posts: 10
|
 Posted: Sun Feb 27, 2011 11:50 am Post subject: Gateway not gatewaying |
 |
|
This might well be user error, but I can't get my dual homed server to gateway.
There are two NICs:
| Code: | # The internal network interface
auto eth0
iface eth0 inet static
address 192.168.1.4
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
# Outside interface
auto eth1
iface eth1 inet static
address 192.168.2.4
netmask 255.255.255.0
network 192.168.2.0
broadcast 192.168.2.255
gateway 192.168.2.1 |
The routing table looks OK to me:
| Code: | # ip route
192.168.2.0/24 dev eth1 proto kernel scope link src 192.168.2.4
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.4
default via 192.168.2.1 dev eth1 metric 100 |
Forwarding is enabled:
| Code: | # cat /proc/sys/net/ipv4/ip_forward
1 |
I was using shorewall, but I cleared it when the problem struck:
| Code: | # iptables --list
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination |
But I can't ping even from one NIC to the other:
| Code: | # ping -I eth0 192.168.2.4
PING 192.168.2.4 (192.168.2.4) from 192.168.1.4 eth0: 56(84) bytes of data.
From 192.168.1.4 icmp_seq=1 Destination Host Unreachable |
It was working, until I was messing around with the patch cables and managed to get them swapped over. I've corrected them now but it no longer seems to pass packets between interfaces. I noticed because squid (transparently proxying) stopped working, other stuff on the box (postfix, dovecot, getmail, dnsmasq) is working fine, the internal NIC is visible from the internal network, the external NIC can access the 'net.
I've rebooted (more than once) but the problem persists, any network gurus spot anything obviously wrong?
TIA
sproot |
|
| Back to top |
|
 |
Dutch_Master
LXF regular
Joined: Tue Mar 27, 2007 2:49 am
Posts: 2354
|
| Posted: Sun Feb 27, 2011 4:28 pm Post subject: |
|
|
As you swapped over the cables, the router (assuming you use one) has given them a TTL in its cache. Reset the router (or flush the entries from the cache) then reboot the network interfaces (ifdown eth0/1 then ifup eth0/1) on the server. Find out why Squid isn't working, fix it and have it restart.
PS: are you sure the netmasks are correct? With 255.255.255.0 they can only see other interfaces in the 192.168.1.x or 192.168.2.x ranges... |
|
| Back to top |
|
|
indie
LXF regular
Joined: Thu Dec 06, 2007 12:00 pm
Posts: 135
|
| Posted: Mon Feb 28, 2011 1:36 pm Post subject: Re: Gateway not gatewaying |
|
|
| sproot wrote: |
| Code: | # ping -I eth0 192.168.2.4
PING 192.168.2.4 (192.168.2.4) from 192.168.1.4 eth0: 56(84) bytes of data.
From 192.168.1.4 icmp_seq=1 Destination Host Unreachable |
|
You're trying to ping eth1 (192.168.2.4) from eth0 (192.168.1.4) when there's no route to 192.168.2/0/24 from eth1, it won't work.
Connect another machine to eth0 and make sure that's got it's default route set to 192.168.1.4 then try pinging 192.168.2.4 and that should work. |
|
| Back to top |
|
|
sproot
Joined: Mon Aug 13, 2007 9:55 pm
Posts: 10
|
| Posted: Fri Mar 04, 2011 1:42 pm Post subject: |
|
|
Yeah, user error 
I was expecting that doing, for example, a traceroute from 192.168.1.x to 192.168.2.x would show 192.168.1.4 and 192.168.2.4 as hops, because the gateway is routing between the two networks. It doesn't, it just shows the source interface as a hop.
The issue was that the return route from the default gateway on the 192.168.2.0 network was wrong, packets were going out but didn't have a route back. When I fixed that it started working.
Doh!
Thanks
sproot |
|
| Back to top |
|
|
| View previous topic :: View next topic |
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
