- 2x WAN, both having a static public IP (called WAN_p1 and WAN_p3 in this example)
- 1x LAN
- You want to use WAN_p1 by default and the backup connection only if the main one fails.
- In both cases, the current IP should be updated to an external DDNS service, so incoming connections always use an IP/connection which is currently working.
First make sure both WAN connections are working and the firewall settings are correct.
E.g. you need at least some NAT masquerading rules and maybe a hairpin rule (sort of loopback):
/ip firewall nat
add action=masquerade chain=srcnat comment="masquerade all outgoing" out-interface=WAN_p1
add action=masquerade chain=srcnat comment="masquerade all outgoing" out-interface=WAN_p3
Configure DHCP Client (if needed)
Even if you have static IPs for your WAN connections, some providers need a DHCP client anyway to be usable, especially if there is a redial enforcement e.g. after 24 hours.
It should be enough to add a simple DHCP client with default options.
To give one WAN interface a higher usage priority, give the other one a higher distance value like 1.
The commands could look like:
add comment="first one, higher priority" default-route-distance=0 dhcp-options=\
hostname,clientid disabled=no interface=WAN_p1
add comment="backup" dhcp-options=hostname,clientid \
Make sure both connections get their “static” IP and are up and running.
Choose at least 2 external hosts with static IP addresses. I took the Google DNS servers 22.214.171.124 and 126.96.36.199 as they are quite reliable for connectivity checks.
First, we define that 188.8.131.52 should always be connected to via the main WAN connection, and 184.108.40.206 via the backup connection:
add dst-address=220.127.116.11/32 gateway=WAN_p1 scope=10
add dst-address=18.104.22.168/32 gateway=WAN_p3 scope=10
Scope = only use this one gateway
I spent many hours trying to get a well-working failover with routes (check-ping, route distance etc.), but ended up using Netwatch which is the best way now in my opinion. I added it at the bottom of this tutorial.
Configure Netwatch (E-Mail)
You might want to get notifications if one of your connections goes down.
First, enter your email server’s settings unter Tools -> Email.
Then open Tools -> Netwatch and add a new host. I also choose 22.214.171.124 and 126.96.36.199 for this, because of the route settings the first one is sort of “mapped” to the main connection, the second one to the backup WAN.
For the Up and/or Down event, enter a command to send an e-mail to yourself.
The full command:
add comment="onlinecheck wan_p1" down-script="tool e-mail send [email protected] subject=\"wan_p1 is down\"" host=188.8.131.52 timeout=10s \
up-script="tool e-mail send [email protected] subject=\"wan_p1 is up\""
add comment="onlinecheck wan_p3" down-script="tool e-mail send [email protected] subject=\"wan_p3 is down\"" host=184.108.40.206 timeout=10s \
up-script="tool e-mail send [email protected] subject=\"wan_p3 is up\""
You should get a first notification after a few seconds.
Configure Dynamic DNS Service
From RouterOS v6.14, the system offers a very convenient DDNS service itself, you do not even have to register anywhere.
The only thing you have to do is activate the checkbox “DDNS Enabled” under IP -> Cloud.
Command as alternative:
/ip cloud set ddns-enabled
After a few seconds, you should get your personal public DNS name.
You can e.g. enter this DNS name as a CNAME in your domain settings. Note for the root domain entry (TLD), e.g. “example.com”, you cannot enter CNAMEs. I prefer to add both WAN IPs as A names for the root entry, and the up-to-date CNAME for any subdomains like www, * etc.
You might encounter issues regarding the availability for incoming connections via both WAN providers. E.g. if both WAN connections are up and you ping your WAN_p3 public IP from an external host, you will see the connection in RouterOS, but the ping itself will not succeed. Only after you disconnect WAN_p1, it works.
To solve this, we have use connection/routing marks, so the packets/answers go out where they came in, and vice versa.
Use the mangle table:
/ip firewall mangle
add action=mark-connection chain=prerouting in-interface=WAN_p1 new-connection-mark=WAN1 passthrough=no
add action=mark-routing chain=prerouting connection-mark=WAN1 new-routing-mark=WAN1 passthrough=no
add action=mark-routing chain=output connection-mark=WAN1 new-routing-mark=WAN1 passthrough=no
add action=mark-connection chain=prerouting in-interface=WAN_p3 new-connection-mark=WAN2 passthrough=no
add action=mark-routing chain=prerouting connection-mark=WAN2 new-routing-mark=WAN2 passthrough=no
add action=mark-routing chain=output connection-mark=WAN2 new-routing-mark=WAN2 passthrough=no
add distance=1 gateway=WAN_p1 routing-mark=WAN1
add distance=1 gateway=WAN_p3 routing-mark=WAN2
Configure Netwatch (Failover)
As I described above, I switched from failover via routing to a Netwatch solution which is quite fine and simple, because: You do not have to enter any of your public (maybe dynamic) IP adresses manually in the routing table, and the routes stay clear and understandable.
Set a comment to both of your “main” routes, e.g. for “0.0.0.0 -> WAN_p1”: “Netwatch:WAN1” and “0.0.0.0 -> WAN_p3”: “Netwatch:WAN2”, so you can identify both routes in the Netwatch script.
Edit both entries you created before for your email notifications.
E.g. for 220.127.116.11 (WAN1): Add
Shell1/ip route set [find comment="Netwatch:WAN1"] distance=2;
Shell1/ip route set [find comment="Netwatch:WAN1"] distance=1;
- Do it similar for 18.104.22.168 with “Netwatch:WAN2”
So if Netwatch notices a host and therefore a WAN port is unreachable, it gives the certain route a higher distance (lower priority). As soon as the interface is up again, it changes the distance back to 1.
In my case, WAN_p1 has a higher priority (lower distance) than WAN_p3, which is defined in the DHCPClient (“Default Route Distance”).