It works according to scheme 1 or 2, when eth0 is enabled, the mobile connection does not work, NetworkManager shows that it is active, but it simply cannot be proping, let alone something larger, when you turn off eth0, the mobile connection immediately rises and works, but very I want to make option number 3 and make two connections work at the same time.
Server under CentOS 6.5



iptablesand multiple routing tables. With default settings, multi-gateway configurations work disgustingly. - user194374ppptoeth. There will be two tables. One binds to theppp0interface, the other toeth0. The tables are independent, the definition of belonging to a table is based on theiptableslabels that it puts on the packets, based on the recipient interface of the packet. After such manipulations, two network areas are actually created, the traffic between which cannot be walked and the server works correctly with several Internet connections. PS However, if you are sure that it will not help you - do not use it, nobody forces it. - user194374