DdeC 6 April 2021
Isolate port from bridge

Using WebFig


To remove one port from an existing bridge and set it up on its own subnet, connected to the internet, and serving addresses by DHCP.

- The following assumes you are not connected to the device by the port you plan to change.

- check if the port you want to remove is part of an existing bridge at Bridge>Ports

- if it is, check in Interfaces>Interface if it is a slave port ('S'). If NOT, it is a master port, so removal of it will dismantle the bridge and cause problems possibly including making the device unreachable (eg Ref 1: the 'master' port of a bridged group lends its MAC address to the group). To avoid this, use access by an unrelated port or via Winbox which can connect via a MAC address. Removing a bridge is beyond the scope here.

- when confident of your connection to the device, in Bridge>Ports>select interface and "Remove".

- give the port a new subnet at IP>Addresses>Add New. Note the address is given a mask of /32 (single address); change this to the size of subnet you want e.g. /24. "Network" is the IP address you want for the port, e.g. use '0' in the last field of the address. The 'interface' is the port that is being changed.

- set a new pool for DHCP distribution at IP>Pool, note the name

- activate the DHCP server for this subnet at IP>DHCP Server

- In IP>DHCP Server>Networks enter subnet and gateway IP addresses

- check IP>DHCP Server>Leases

- add the port to 'LAN' in the lists at Interfaces>Interface List. Optional, but important for subsequent firewall settings.

- for IPv6 connectivity, set up IPv6>Addresses, Pool. For downstream host, set up IPv6>ND, for downstream router, IPv6 Server

- uplink: check NAT ('masquerade') set towards WAN port with chain=srcnat at IP>Firewall>NAT. Works for all subnets, not just this one.

- connection between this port and other ports or bridges should be automatic and not require setting (eg see https://forum.mikrotik.com/viewtopic.php?t=104524)

Done


Refs
1. https://forum.mikrotik.com/viewtopic.php?t=142579