TUNNEL SPEED

HI
I WAS IMPLEMENTED A VPN WITH MIKROTIK AS HUB AND OTHER ROUTERS. FOR THIS I USED IPSEC AND PPTP.

I USE DUDE V2.0 TO MONITOR THE ROUTERS AND SPEED OF LINKS.
IF I MAKE THE LINK WITH ROUTER AND MIKROTIK WITH MONITOR
ONLY THE MIKROTIK WITH MASTERING TYPE THE ROUTEROS AND THE INTERFACE (pptp-testuser) I SAW THE LINK TRAFFIC.

IF THE ROUTER IS DISCONNECT AND RECONNECT I LOST
THE INTERFACE (THE INTERFACE IS SAME - pptp-testuser 456)
THE ONLY THING WHO CHANGED IS INTERFACE NUMBER.

CAN I MAKE PERMANENT THE INTERFACE (THE NAME IS NOT CHANGE IN
CONNECT/RECONNECT, ONLY THE NUMBER) ?

THANKS