ppp-client - How to remove Add as default route

RouterOS Beginner Basics
1

I’m connecting with dialup trought a serial modem, apparently it works fine, but if I remove the option in tab

PPP: Add as default route


/interface ppp-client
add add-default-route=yes dial-command=ATD disabled=no  name=\
    ppp-SECONDARY password=xxx phone=xxxxx port=serial0 user=xxxx

then restart connection, the connection keep it’s state in “wait for packets”.
Instead if I leave the flag, it goes on, it dial then autenticate and connect.
Why this happen? I need to use this connection not as default route, would it be possible?

2

Seems to work like this:

min@MikroTik] > /interface ppp-client print 
Flags: X - disabled, R - running 
 0  R name="ppp-SECONDARY" max-mtu=1500 max-mru=1500 mrru=disabled port=serial0 
      data-channel=0 info-channel=0 pin="" user="XXX" password="XXXXX" 
      profile=default phone="" dial-command="ATD" modem-init="" null-modem=no 
      dial-on-demand=yes add-default-route=no use-peer-dns=yes 
      keepalive-timeout=30 allow=pap,chap,mschap1,mschap2

Just another question:

A client ----router A ------------- router B ---- B client

It is possible from client A to comunicate with client B with only dst-nat NAT rules on router B?
i.e. when I torch traffic, I can see request to B from A, but no response from B.