Hello,
a similar problem has already been described in http://forum.mikrotik.com/t/policy-routing-l2tp-and-multiple-wans/36807/1 when alias on one interface - everything works well, but if there aliases on multiple interfaces - does not work on any of the interfaces.
10:33:09 l2tp,info first L2TP UDP packet received from 1.1.1.11
10:33:19 l2tp,info first L2TP UDP packet received from 1.1.1.12
10:33:30 l2tp,info first L2TP UDP packet received from 2.2.2.11
10:33:40 l2tp,info first L2TP UDP packet received from 2.2.2.12
and no authentication attempts
example of config:
# feb/20/2015 13:27:28 by RouterOS 6.27
#
/interface ethernet
set [ find default-name=ether1 ] name=ether1-gateway
/interface vlan
add interface=ether1-gateway l2mtu=1596 name=vlan10 vlan-id=10
add interface=ether1-gateway l2mtu=1596 name=vlan20 vlan-id=20
add interface=ether1-gateway l2mtu=1596 name=vlan300 vlan-id=300
/ip pool
add name=pool-l2tp ranges=192.168.54.0/24
/ppp profile
add change-tcp-mss=no local-address=192.168.243.1 name=profile11
/interface l2tp-server server
set authentication=pap,chap enabled=yes max-mru=1460 max-mtu=1460
/ip address
add address=10.3.3.13/26 interface=vlan300 network=10.3.3.0
add address=1.1.1.2/24 comment=ip1.2 interface=vlan10
add address=1.1.1.3/24 comment=ip1.3 interface=vlan10
add address=2.2.2.2/24 comment=ip2.2 interface=vlan20
add address=2.2.2.3/24 comment=ip2.3 interface=vlan20
/ip route
add distance=1 gateway=10.3.3.1
/ppp secret
add name=user1.2 password=pass1.2 profile=profile11
add name=user1.3 password=pass1.3 profile=profile11
add name=user2.2 password=pass2.2 profile=profile11
add name=user2.3 password=pass2.3 profile=profile11
clients must connected to 1.1.1.2-3 and 2.2.2.2-3