Conflict of two DHCP Servers on same network over openvpn TAP bridge (AC68U + Mikrotik hex)

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tymchyshyn90

Occasional Visitor
Hello!
I have OpenVPN TAP server on AC68U Merlin
And Mikrotik - client
Network bridged as i want

Asus IP - 192.168.0.1, DHCP pool - 192.168.0.3-99
Mikrotik IP - 192.168.0.101, DHCP-pool 192.168.0.102-200
Exept this, ASUS have IPv6

When I made this bridge - at first everything worked well. Devices from Asus LAN receive IP from ASUS DHCP. Devices from Mikrotik LAN received IPv4 from Mikrotik DHCP and IPv6 from ASUS. I reallly liked it)
But after few days I saw that some Mikrotik LAN devices receive IP from ASUS, and gateway too. It's problem, because OpenVPN speed is not very fast and ASUS CPU load well...

How can I restrict this?
 

tymchyshyn90

Occasional Visitor
I found some solution - block 67 and 68 ports (DHCP ports) in firewall. This should work. But then devices from Mikrotik's LAN will not receive IPv6 address
 

ColinTaylor

Part of the Furniture
Merlin's OpenVPN server and client doesn't support IPv6.
 

tymchyshyn90

Occasional Visitor
Merlin's OpenVPN server and client doesn't support IPv6.
Mikrotik connect to openvpn server over IPv4. But this is not TUN, it's TAP bridge. All devices are on same network 192.168.0.0/24. ASUS receive all Mikrotik's LAN devices MAC and give them IPv6 address
 

Morris

Senior Member
There should only be one DHCP server in a subnet unless they are specifically designed to work together.

Morris
 

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