Thanks for your response!
In reply to your question…
192.168.1.1 is the LAN IP of the old DSL modem.
192.168.2.1 is the LAN IP of the new DSL modem.
Did you check your DNS settings like mentioned in post 2?
Yes, I did.
As I said in my first post, I have played around with various combinations of DNS server settings (both Google as well as ISP provided) in the Nethserver DNS section.
If someone has a running configuration with two red NIC, pretty please drop a line with details on how they have set it up? 
I have installed a second wan yesterday evening, I had no problems at all, it works.
Having said that, I don’t know what could have gone wrong in your case.
Some commands useful for debugging:
# shorewall status -i | grep Interface
Interface en2 is Enabled
Interface en4 is Enabled
To force enabling a disabled interface:
shorewall enable en4
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Sorry, was offline for the past few days.
Do let me know if I can run any other commands which will provide further information, which I can then share with you.
Meanwhile, if it’s okay with you, could you please share the IP configurations of both your red NIC? Since the configuration of both the DSL modems is in my control, I can try replicating your test setup.
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@filippo_carletti I set the multi WAN mode to Active backup, and configured the NIC as follows:
enp3s0
enp3s0 - pci Realtek Semiconductor Co. Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06)
Link status is up
Speed 100 Mbit/s
Driver r8169
Mac address [redacted]
Role RED
IP: 192.168.1.2
Subnet: 255.255.255.0
Gateway: 192.168.1.1
Name: red40
Weight: 100
enp4s0
enp4s0 - pci Realtek Semiconductor Co. Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06)
Link status is up
Speed 100 Mbit/s
Driver r8169
Mac address [redacted]
Role RED
IP: 192.168.15.2
Subnet: 255.255.255.0
Gateway: 192.168.15.1
Name: red41
Weight: 100
Next, I checked this:
# shorewall status -i | grep Interface
Interface enp3s0 is Disabled
Interface enp4s0 is Disabled
Thus, ran the command you provided, to get both of them up. So, in the Dashboard section, the Multi WAN section showed both as UP.
However, still unable to get internet access. Tried ping from the server:
# ping google.com
ping: google.com: Name or service not known
Please note that this server has the ASUS H270M Plus motherboard with the problem where, on switching on the server, we need to run the “signal-event interface-update” command to get the network up. Please refer to this post where you and @giacomo have advised us, previously: Networking issues after installing AD
The weird thing is, we have to physically unplug any one of the two NIC and only then does the system work (after running the “signal-event interface-update” command). Simply releasing the role doesn’t work.
Please let me know if there’s any further data I can provide you, to help figure this out.
Have fixed the problem. @filippo_carletti, @giacomo please note that it seems that Nethserver is unable to handle static IP settings.
Following was the fix, for anyone else struggling with the issue:
- Release roles of both the red NIC
- Switch both modems to DHCP mode and perform DHCP IP reservation for both the red NIC
- Configure the red NIC in Network section, as required
- Reboot!
Note that switching over to DHCP has also fixed the issue where the network would remain down (on restart) and we had to run the “signal-event interface-update” command.
Thanks for everyone’s help! 
4 Likes
I have a Multi Wan configured. Red1 (static IP), Red2 (DHCP). When the Internet goes to red1, the system automatically switches to red2. But back switching does not happen. Only if you physically disconnect the cable from red2, then only red1 switches.
DNS for connection testing 8.8.8.8
How to solve this problem?
P.S. Also the status is not correctly displayed.
It shows red1 UP, but the Internet works through red2.
It shows red2 down but in fact the Internet works through red2.
This is visible if you select Diagnostics - External Public IP
red1 static ip.
red2 DHCP.
The problem occurs approximately every 2-3 days. The red1 connection is disconnected (but in the panel it is displayed as up), red2 is turned on (in the panel it is displayed as down).
If you connect the red1 cable to another computer, the Internet works without problems.
Switching from red2 to red1 does not happen. How to solve this problem?
AFAIK NethServer MultiWAN diagnose the connection status with ping to specific ip addreses wrote on WAN and MultiWAN configuration.
Also the time and the number of attempts and errors is configurable.
Therefore, i suggest you to change a bit the configuration and… do some tests.
How to set automatic return from red2 to red1? Help is needed!
Switch it’s automatic. If it’s not happening it may be caused by the router.
You could debug it with two tcpdump (one per red interface) looking for icmp packets.
Can you write in detail how to do this?
tcpdump -nn -p -i <red_eth_name> icmp
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Yes, I executed this command. Indicates that there is a connection. But switching does not occur.
There is a problem. Multi WAN is configured by red1 and red2.
Red1 static ip channel 100 megabits (weight indicated 100)
red2 is a backup channel adsl, 15 megabits (weight indicated 50)
Constantly switching to red2, no return to red1.
If you disable red2, then the Internet through red1 works stably.
We had some issues with some routers. As I said you need to debug icmp through red1 with tcpdump when red1 is down.
We need to see tcpdump output as a copy and paste.
In our case, the workaround has been to change ping interval to 35 seconds.