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Operating Systems Linux Ubuntu Ubunut iptable not routing trafic between eth1 and eth0 Post 302638425 by florin.bv on Thursday 10th of May 2012 09:17:41 AM
Old 05-10-2012
Ubunut iptable not routing trafic between eth1 and eth0

hello,
first of all i am new to unix so maybe my problem is very easy for many of you but is very important to me.

So the idea is that i want to use a ubuntu 10.4 machine as a router from eth0 to eth1.
but the traffic routing is nor working properly

i configured the 2 interfaces to be part of 2 subnets and then i tried to use iptables command.
sudo sysctl -w net.ipv4.ip_forward=1
iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT
iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT


the result was
sudo iptables -L -n -v
Chain INPUT (policy ACCEPT 5493 packets, 4815K bytes)
pkts bytes target prot opt in out source destination

Chain FORWARD (policy ACCEPT 254 packets, 16979 bytes)

pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- eth0 eth1 0.0.0.0/0 0.0.0.0/0
1 60 ACCEPT all -- eth1 eth0 0.0.0.0/0 0.0.0.0/0

Chain OUTPUT (policy ACCEPT 5349 packets, 888K bytes)

pkts bytes target prot opt in out source destination


unfortunately there was no trafic between the interfaces an even i could ping eth1 and eth0 from the pc-s from the subnetworks i was unable to ping from one pc to the other

digging more i found that if i run
sudo iptable -t nat -A POSTROUTING -j MASQUERADE everithing works perfect

unfortunately i need the ipaddresses of the PC and the NAT here is not doing more wrong than good.

please give me some ideas why this hapens

i add here the result of the route command
destination Gateway Genmask Flags Metric Ref Use Iface
100.10.10.0 * 255.255.255.0 U 1 0 0 eth1
192.168.10.0 * 255.255.255.0 U 1 0 0 eth0
link-local * 255.255.0.0 U 1000 0 0 eth0
default 192.168.10.1 0.0.0.0 UG 0 0 0 eth0
 

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IFSCHEME(8)							     Commands							       IFSCHEME(8)

NAME
ifscheme - scheme control for network interfaces SYNOPSIS
ifscheme [-v] [[-s] newscheme] mapping <interface> script ifscheme-mapping DESCRIPTION
ifscheme allows you to change network configuraton schemes or query the current scheme. It integrates with the ifup(8) command and inter- faces(5). For example, you might use this program to configure a "home" scheme and a "work" scheme for a network device on a laptop. When you move between home and work, a simple command can reconfigure your networking. If you run the program with no parameters, it will tell what the current network scheme is. The ifscheme-mapping utility is used to tell the ifup and ifdown utilities about the current scheme. OPTIONS
-v --verbose Run in verbose mode. This is passed in to the ifup and ifdown programs as well. -l --list list all schemes available/defined in /etc/network/interfaces. newscheme -s newscheme --scheme newscheme Change to a new network configuration scheme. When the scheme is changed, network interfaces that were using the old scheme will be taken down and brought back up to use the new configuration scheme. -s or --scheme are mandatory if newscheme begins with a -. CONFIGURATION
To make the program do anything useful when a scheme is selected, you must edit /etc/network/interfaces to add a mapping for the interface (or interfaces) that can be controlled on a per-scheme basis. Suppose you want to control eth0 in this way. You might have an existing eth0 configuraton in there, such as: auto eth0 iface eth0 inet static address 192.168.1.5 netmask 255.255.255.0 gateway 192.168.1.1 To change this so you can chose between static routing and dhcp, replace it with the following (it helps to ifdown the interface first). auto eth0 mapping eth0 script ifscheme-mapping iface eth0-home inet static address 192.168.1.5 netmask 255.255.255.0 gateway 192.168.1.1 iface eth0-work inet dhcp Now if you run "ifscheme home" and ifup the interface, you'll get the eth0-home configuration stanza. If you run "ifscheme work", it will be changed to the eth0-work stanza. You can add additional stanzas as desired, but the label must always be of the form <hardware inter- face>-<scheme name>. If you have a second interface (perhaps a wireless network card on eth1), you can duplicate the above for that interface, changing the eth0 and the configuration details as appropriate, but remember to add an iface stanza for every scheme name for the second interface. FILES
/etc/network/interfaces the interfaces definition file /etc/network/run/scheme the current scheme /etc/network/run/ifstate a record of the current state of the interfaces, managed by ifup and ifdown BUGS
All schemed interfaces will have the same scheme. Any schemed interface which does not have an entry for the current scheme and is not configured when the scheme is changed will not be suc- cessfully configured when it is brought up. SEE ALSO
interfaces(5) ifup(8) ifdown(8) DISTRIBUTION
Redistribution is subject to the GNU public license. AUTHORS
Joey Hess <joey@kitenet.net>, Peter Wilson <pwilson@cs.hmc.edu> IFSCHEME(8)
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