Backup Internet connection with a 4G Ethernet router

Question

Hello fellow Sophos users, 
 Happy to have joined this community as this is my first ever post. I just need little guidance as i'm fairly new to Sophos: 
 I would like to add a secondary WAN connection (4G) as backup for specific servers that are remotely accessible. We currently have one single LAN with no other subnets or Vlans. I have at my disposal a Huawei 4G wireless router which has 1x Ethernet port (B5328 Model) and since i'm not really familiar enough with Sophos UTM, i would like to get some guidance on how to set this up. What i want to know is, the type of interface for the 4G Router which will be connected via Ethernet one one of the UTM ports and how to set it up as backup for only those specific servers that i mentioned earlier. 
 I don't know if i made it clear enough but i'd be happy to elaborate on any of these points if you have any questions. 
 Regards, 
 Zak

BAlfson · Accepted Answer

In this scenario, your top Multipath rule must be one that binds 'Any -> Any -> Any' to the other interface. That rule would not be necessary if your backup interface were not in 'Active'. 
 In either case, if nothing other than the servers should use the backup connection, you need to have at the bottom of the list another multipath rule like the first except that you must de-select ' Skip rule on interface error' in 'Advanced'. 
 Cheers - Bob

sachingurung · Answer

Hi Zak, 
 Welcome to the Sophos Community! 
 Define an interface as Ethernet Type and connect the 4G router to it physically. You will find more information here: How to define a network interface . Now you need to either define a static IP address within the subnet of the router's IP address and set the Gateway address as the routers IP address OR select the option of Dynamic ipv4, if the router acts as a DHCP server. Save the configuration and then define a multipath rule for the servers . Add the 4g WAN interface as a standby interface in uplink balancing. 
 Thanks,