CentOS Dual WAN - Issue

[wizzkid]

Hi,

I setup CentOS with Dual WAN.

eth0 = line1
eth1 = line2

If I setup both WAN, the default connection and gateway will pass thru eth1 (line2),

If I issue command ifdown eth1, the internet will be gone though eth0 is also WAN, even I route add default gateway using the gateway of eth0, i cannot access the internet even ping 8.8.8.8

The only way to use the eth0 is to remove the cable and configuration of eth1.

I want to be able to use both WAN interface for fail-over.

If I issue ifdown eth1 , eth0 will take over, vice-versa.

hope you can help.

Sincerely,
WizzKid

[gstewart]

Are you trying to configure NIC failover? Or, are you configuring each interface with a different IP address?

Which version of CentOS?

Is the box behind a firewall? Or, is it connected to something like a cable router?

Can you provide dummy IP address(es) that illustrate(s) your configuration? What about your ifcfg-ethX files (please dummy-up the IP addresses).

If you are trying to use a single IP address on the network, but assign it to two NICs at the same time for fault tolerance, you want to configure NIC bonding. And, there are changes in how to go about it depending on the version of CentOS you are using.

[aruntomar2001]

try ISPunity

rubygems.org/gems/ispunity
spunity.com/

[wizzkid]

Thanks Guys,

This is fixed. just a routing issue.

[wizzkid]

Hi Everyone,

Got an issue with fail-over

My reference ( - FaTaL SiTe - )

Interfaces
eth0 = LAN
eth1 = WAN1 - 58.71.xx.xx - IGATE
eth2 = WAN2 - 202.78.xx.xx - BTEL

Working with Load Balacing.

[root@ ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
58.71.xx.xx     0.0.0.0         255.255.255.240 U     0      0        0 eth1
202.78.xx.xx   0.0.0.0         255.255.255.240 U     0      0        0 eth2
10.10.10.0      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 eth2
0.0.0.0         58.71.xx.xx     0.0.0.0         UG    0      0        0 eth1

[root@ ~]# ip route
58.71.xx.xx/28 dev eth1  proto kernel  scope link  src 58.71.xx.xx
202.78.xx.xx/28 dev eth2  proto kernel  scope link  src 202.78.xx.xx
10.10.10.0/24 dev eth0  proto kernel  scope link  src 10.10.10.1
169.254.0.0/16 dev eth2  scope link
default
        nexthop via 58.71.xx.gw  dev eth1 weight 1
        nexthop via 202.78.xx.gw  dev eth2 weight 1

When I issue command " ifdown eth1 " it will automatically switch to eth2 (BTEL)

Here's my routing table when one link is down thru ifdown command.

[root@GFWPROX ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
202.78.xx.xx   0.0.0.0         255.255.255.240 U     0      0        0 eth2
10.10.10.0      0.0.0.0         255.255.255.0   U     0      0        0 eth0
0.0.0.0         202.78.123.97   0.0.0.0         UG    0      0        0 eth2

[root@GFWPROX ~]# ip route
202.78.xx.xx/28 dev eth2  proto kernel  scope link  src 202.78.xx.xx
10.10.10.0/24 dev eth0  proto kernel  scope link  src 10.10.10.1
default via 202.78.xx.gw dev eth2

The problem is that, When the ISP is really down, it doesnt switch automatically. the routing table is like as if you're still in load balacing mode. I even tried to switch off the ISP's model of eth1 , eth2 doesnt take over, and the internet is gone. I have to issue the command ifdown ethx.

I followed the above link as my reference including the gwping file.


Here's my iptables for your reference.

iptables -A INPUT -i eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -i eth2 -m state --state ESTABLISHED,RELATED -j ACCEPT

# set this system as a router for Rest of LAN
iptables --table nat --append POSTROUTING --out-interface eth1 -j MASQUERADE
iptables --table nat --append POSTROUTING --out-interface eth2 -j MASQUERADE
iptables --append FORWARD --in-interface eth0 -j ACCEPT

Hope you can help.

[wizzkid]

I saw the issue, it is in fact the routing table doesnt get save.

Based on the site I provided earlier, here's the routing table (I adjusted based on my ip assignment)

ip route add 172.16.0.0/24 dev eth0 src 172.16.0.100 table ROL
ip route add default via 172.16.0.1 table ROL
ip route add 10.1.0.0/24 dev eth1 src 10.1.0.100 table DHIRAAGU
ip route add default via 10.1.0.1 table DHIRAAGU
ip rule add from 172.16.0.100 table ROL
ip rule add from 10.1.0.100 table DHIRAAGU

However, when I issue command service network restart, the above will not get save to the routing table.

Is there a way to save them ?

[gstewart]

Use rule-ethX and route-ethX files in /etc/sysconfig/network-scripts/

blog.mc-thias.org/?title=routing-with-linux-when-using&more=1&c=1&tb=1&pb=1

[wizzkid]

Thanks, gstewart, and sorry for posting the same issue on another thread. I got this working already.

Now, I have another question, since I got dual wan / load balancing work, How can I forward a specific traffic to a certain interface?

eg.

IP block 202.123.123.0/24 will be forwarded to eth1 (both incoming and out going traffic)?


Thanks