How to properly configure Mikrotik for 2 providers, one for the Internet, the second for telephony?

Question

SIP

There is one provider for Internet access, connected to the ether1 port, the second cable for IP telephony, connected to ether5. There are 2 phones in the local network, they are connected to the provider's PBX.
The problem is that the interlocutor is periodically not heard on the phones. Screenshots of the settings are attached. RouterOS version 6.47.3
ether1: ip xxx16/24 gw xxx1
ether5: ip 10.yy11/24 gw 10.yy1
ISP PBX 17.zz4

Answer 1

I think it is necessary to mark traffic from phones, and masquerade them into the required interface (the rule for masquerading traffic with marking should be higher than the rule without marking), so the source address will be replaced with the IP from the interface. If on the second interface ip is on dshsp, then turn off the default route for the client and set a static route with a lower weight than the main one (or make the main one have more weight). At the very route of the route, the mark still needs to be put.
and yes, SIP ALG must be disabled.
The weight of the route with marking should be less than without marking, otherwise the traffic will flow into the route with less weight, without marking
And one more thing, because on the second interface you have a local address, then you get a double nat - this will have a bad effect on sip traffic, it may not pass at all.

Answer 2

Write to the Mikrotik group https://t.me/mikrotikme , it has a lot of real-time certificate specialists who will help with the case.
Here is the setup prese: https://mum.mikrotik.com/presentations/RU19R/prese...

Answer 3

I wonder what external IP the phone specifies in the SIP header) If the phone does this using STUN, then it can specify the IP of the first provider. It is also not clear how correctly SIP ALG works with two providers.
Try to prevent phones from accessing the Internet through the first provider.