openvpn server mac-address changes on every backup

RouterOS Beginner Basics
1

Greetings, All!
ROS: 5.14
I’m writing script for backup MT configuration in plain text and binary backup.
Here is line from script:

ssh -i ~/.ssh/id_dsa $1 "/system backup save name=backup ; /export file=export"

I have changed nothing but two versions of /export file=config files are different, there is diff:

 /interface ethernet
@@ -124,7 +124,7 @@
     default-encryption enabled=no max-mru=1460 max-mtu=1460 mrru=disabled
 /interface ovpn-server server
 set auth=sha1,md5 certificate=none cipher=blowfish128,aes128 default-profile=\
-    default enabled=no keepalive-timeout=60 mac-address=FE:30:E6:63:7B:04 \
+    default enabled=no keepalive-timeout=60 mac-address=FE:97:44:5D:3C:83 \
     max-mtu=1500 mode=ip netmask=24 port=1194 require-client-certificate=no
 /interface pptp-server server
 set authentication=mschap1,mschap2 default-profile=default-encryption \

Further investigation make me think this is a very strange behavior, on every execution of /system backup save mac address changed

[configurator@MikroTik] > /int ovpn-server server print
                     enabled: no
                        port: 1194
                        mode: ip
                     netmask: 24
                 mac-address: FE:67:92:BA:55:74
                     max-mtu: 1500
           keepalive-timeout: 60
             default-profile: default
                 certificate: none
  require-client-certificate: no
                        auth: sha1,md5
                      cipher: blowfish128,aes128




[configurator@MikroTik] > /system backup save name=backup
Saving system configuration
Configuration backup saved




[configurator@MikroTik] > /int ovpn-server server print  
                     enabled: no
                        port: 1194
                        mode: ip
                     netmask: 24
                 mac-address: FE:D4:BD:4A:89:9B
                     max-mtu: 1500
           keepalive-timeout: 60
             default-profile: default
                 certificate: none
  require-client-certificate: no
                        auth: sha1,md5
                      cipher: blowfish128,aes128

Is there are any reasonable explanation of this behavior?

2

I know it’s been a while, and probably you solved this… but I came with a solution for this problem.
I use Rancid for configuration control. The only thing that annoys me is that it alerts about things that are useless. One of them is this MAC address issue.
I read that the ovpn-server has the MAC address created dynamically and it changes every once in a while.
So, if you set it up statically, even if you are not running the ovpn-server service, the alerts stop coming.

interface ovpn-server server set mac-address=11:22:33:44:55:66