I tried marking udp/123 traffic with via-lte mark in prerouting/input chains and then adding the routing mark based on the packets or connections that have the via-lte mark but this doesn't seem to be working.
All the clients in the network can successfully use NTP but the NTP client in RouterOS was stuck on Waiting indefinitely. (This is because the ISP I am avoiding here blocks NTP Traffic).
Then I tried adding this mangle rule.
chain=output action=mark-routing new-routing-mark=lte-failover passthrough=no protocol=udp dst-port=123 log=yes log-prefix="route-over-lte-mark-added"
I had also added a `log` rule that simply logs all udp/123 traffic and I see stuff like this,
ntp input: in:lte-vlan out:(unknown 0), src-mac 54:0d:f9:f2:f8:de, proto UDP, p.q.r.s:123->a.b.c.d:123, NAT p.q.r.s:123->(x.y.z.w:123->a.b.c.d:123), len 76
a.b.c.d is the address of the WAN interface I am trying to avoid and
x.y.z.w is the address of the WAN gateway I want to use.
I don't understand what's happening here?