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Old 11-02-2015, 03:40 PM   #1
xtansat
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Registered: May 2015
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Angry masquerading and network configuration


Hi all,
i am try to share internet on two different LANs using masquerading.
here are the details of my setup:
i have one server(name server1) have CentOS-7.i want to configure it as router. it has three interfaces
eth0: is connected with internet router that have IP address 192.168.0.1/24, here are the configuration of eth0
IP address: 192.168.0.100/24
default Gateway: 192.168.0.1
default DNS: 192.168.0.1

eth1: connected with network 10.0.0.0/8
ip: 10.0.0.1
default Gateway: 10.0.0.1
default DNS: 192.168.0.1

eth2: connected with network 172.16.0.0/16
ip: 172.16.0.1
default Gateway: 172.16.0.1
default DNS: 192.168.0.1
********************************************
on server1 i perform following steps:
Step 1: enable port forwarding
echo 1 > /proc/sys/net/ipv4/ip_forwarding
Step 2: firewall-config and enable masqurading by clicking on check box.
*********************************************
Problem Description:
i can not access internet from clients both on LAN1 and LAN2.
when i check internet is also not working on server1.
when i try to ping 8.8.8.8 i get following error message.

From 172.16.0.1 icmp_seq=1 Destination Host Unreachable
From 172.16.0.1 icmp_seq=2 Destination Host Unreachable
From 172.16.0.1 icmp_seq=3 Destination Host Unreachable

****************************************************
if i disable both eth1 and eth2 then internet start working.
 
Old 11-02-2015, 04:33 PM   #2
wildwizard
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You can only have 1 default gateway, remove the extra gw settings on the lan side.
 
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Old 11-02-2015, 05:27 PM   #3
berndbausch
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Registered: Nov 2013
Location: Tokyo
Distribution: Redhat/Centos, Ubuntu, Raspbian, Fedora
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To elaborate on wildwizard's answer,
Quote:
From 172.16.0.1 icmp_seq=2 Destination Host Unreachable
means that the server wants to route 8.8.8.8 packets via eth2, not eth0 as intended. When you check your routing table (ip route command), you will probably see several defaults, which causes confusion. How is the system to know which default to use?
 
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Old 11-02-2015, 06:47 PM   #4
xtansat
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Registered: May 2015
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Hi Thank you for your help, will you please advise how to set it to eth0.
Best Regards,
Tanveer Akhter Satti
 
Old 11-02-2015, 06:51 PM   #5
xtansat
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Registered: May 2015
Posts: 9

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hi wildwizard,
please advise that it is ok that i set default gateway 192.168.0.1 for all interfaces
Best Regards
 
Old 11-03-2015, 01:45 AM   #6
berndbausch
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You just leave the GATEWAY clause out of the config files for eth1 and eth2. I.e. you don't configure a gateway for them. See also the Red Hat networking guide.
 
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