Hello everyone.
I got strange issues on a coupe of RB750GL routers under RouterOS 6.23 and 5.20. NAT is counfigured as follows:
0 ;;; default configuration
chain=srcnat action=masquerade out-interface=ether1-MAIN-Starlink
log=no log-prefix=""
"ether1-MAIN-Starlink@ is an interface pointing to ISP. I have a static route to my main network
# DST-ADDRESS PREF-SRC GATEWAY DISTANCE
...
2 A S 10.0.0.0/8 pptp-out1 1
“pptp-out1” here is a standard PPTP interface created by PPTP client. Everything works OK, but, from time to time some of our IP phones Cisco SPA502G are unable to register on out PBX, which address is 10.0.1.78. Logging shows following:
82 Feb/02/2015 13:38:40 memory firewall, info forward: in:ether3-LAN out:pptp-out1, src-mac 30:e4:db:80:b0:4d, proto UDP, 10.13.1.41:5060->10.0.1.78:5060, len 433 <-- an IP phone successfully connects to PBX
...
84 Feb/02/2015 13:38:48 memory firewall, info forward: in:ether3-LAN out:pptp-out1, src-mac 30:e4:db:80:b0:77, proto UDP, 10.13.1.61:5060->10.0.1.78:5060, NAT (10.13.1.61:5060->external IP address of RB750GL:1076)->10.0.1.78:5060, len 491 <-- an IP phone is unable to connect
I am quite confused, why some clients are connecting correctly while others are not. Could someone explain to me, why this happens?
Thanks in advance.