Hello i have my old router rb750 Gr2 aka Hex and i need to set it as a poe switch.
is it possible?
when i put all ports to bridge i cant set dhcp client to any port...
thats wiring:
eth1 - router(crs326) +poe
eth2 - client
eth3 - client
what i need to do to make this working?

Bind DHCP client to bridge.

i did and router offering an address but hEX didnt get it...

Any firewall rules?

accept ICMP, SSH, Winbox, related and established
drop anything else.

turning firewall off dont make any change.

when i bond all the interfaces suddenly dhc client works but i cant connect to any clients connected to hex.
clients have ip and dns and have acces to internet but not to lan.

If you're going to use hEX as switch, the you presumably have another device as router. So you should disable all firewall rules for chain=forward, disable any DHCP server that might be still there and most definitely disable NAT that might still be active. If you need firewall to protect hEX itself from LAN hosts, then you need firewall rules for chain=input, but you need to allow connections between hEX UDP port 68 and DHCP server UDP port 67.

It might be actually easier to set things up by resetting hEX to state without any configuration. You'd have to do initial configuration using winbox via MAC.

after i cleaned configuration:
i just put all ports to bridge and start dhcp client on bridge.
hex got ip but.... hex clients after got ip have internet but cannot communicate via lan...

Which is it: a) wireless clients can not communicatewith each other or b) wireless clients can not communicate with any LAN host, including wired?

If it's a), then check setting of default-forwarding (should be yes). The other thing (which might cause either effect) is firewall on other LAN hosts which might block connectivity even from LAN hosts.