/ip firewall mangle
add action=jump chain=prerouting comment=adsl_bonding disabled=no dst-port=80,81,82,8080 jump-target=bonding protocol=tcp src-address=192.168.0.0/16
add action=jump chain=prerouting comment="" disabled=no jump-target=bonding src-address-list=other_list
add action=mark-connection chain=bonding comment="" disabled=no dst-address-type=!local in-interface=LAN new-connection-mark=adsl1conn passthrough=yes per-connection-classifier=both-addresses:3/0
add action=mark-routing chain=bonding comment="" connection-mark=adsl1conn disabled=no in-interface=LAN new-routing-mark=main passthrough=yes
add action=mark-connection chain=bonding comment="" disabled=no dst-address-type=!local in-interface=LAN new-connection-mark=adsl2conn passthrough=yes per-connection-classifier=both-addresses:3/1
add action=mark-routing chain=bonding comment="" connection-mark=adsl2conn disabled=no in-interface=LAN new-routing-mark=main passthrough=yes
add action=mark-connection chain=bonding comment="" disabled=no dst-address-type=!local in-interface=LAN new-connection-mark=adsl3conn passthrough=yes per-connection-classifier=both-addresses:3/2
add action=mark-routing chain=bonding comment="" connection-mark=adsl3conn disabled=no in-interface=LAN new-routing-mark=main passthrough=yes

要让哪走上行就new-routing-mark=main 到哪，当然vpn也行。按常规方式添加VPN网关（vpn服务器是要未做NAT伪装的）。

/ip firewall nat
add action=src-nat chain=srcnat comment=ADSL1 connection-mark=adsl1conn disabled=yes src-address=192.168.0.0/16 to-addresses=121.69.45.22
add action=src-nat chain=srcnat comment=ADSL2 connection-mark=adsl2conn disabled=yes src-address=192.168.0.0/16 to-addresses=121.71.114.11
add action=src-nat chain=srcnat comment=ADSL3 connection-mark=adsl3conn disabled=yes src-address=192.168.0.0/16 to-addresses=121.69.47.21
add action=src-nat chain=srcnat comment="" disabled=yes src-address=192.168.0.0/16 to-addresses=221.219.144.111

虽然mark-routing 到了指定的线路，但src-nat 伪装到了ADSL线路IP，回来的数据（下载）就通过ADSL返回了，连接正常建立，当然也就不会断线。

:local curaddress
:local newaddress
:local status
:local x
:set x 3
:for i from=1 to=$x do={
    :set status [/interface get [/interface find  name=("pppoe-out" . $i)] running]
    :if ($status=true) do={
    :set newaddress [/ip address get [/ip address find dynamic=yes interface=("pppoe-out" . $i)] address ]
    :set newaddress [:pick $newaddress 0 [:find $newaddress "/"]]
    :set curaddress [ /ip firewall nat get [/ip firewall nat find comment=("ADSL" . $i)] to-addresses ]
    :if ($curaddress != $newaddress) do={
       /ip firewall nat set [ /ip firewall nat find comment=("ADSL" . $i) ] to-addresses=$newaddress
       :log info ("Change ADSL" . $i . " NAT IP" )
         }
     }
}

自动修改 NAT ip脚本 注意 comment=ADSL1  这样的格式。

不是所有运营商都会不检测源地址是否合法，具体能否这样成功应用，自己测