One of my customer have 1 head office and 2 branches different locations. They have a server and two internet lines (ADSL and VDSL2) in head office. Branchs have own servers and internet lines. All lines have static ip's. Servers are linux ubuntu. They have 3 web sites, mail server (postfix), mysql, etc.
On modems, nat and dhcp services is working. They have noip.com service for nameservers.
1) Internal users cannot access to internal web sites via domains. (server and users in same subnet)
2) They using just one line actively, second line for backup. How can to use two internet connections same time in a network ?