Even if i request static ip address from ISP, the static ip is also delivered thru DHCP.
Ofcorse you can assign that static IP to an interface without the need of a dhcp client...
Be sure of what you write before you tout it as gospel - this is DHCP but its mostly IPoE which is not your conventional DHCP in a lot of ways - it still hands out a /32 with a PtP style route / gateway, with the DHCP server on the other end likely handling access rights through AAA on the DHCP server (i.e. if the client isnt registered, traffic likely will not flow), not to mention, the changing client IP, and the likelihood of changing gateway depending on what BRAS / BNG the client authenticates against.
@OP - why is your WAN on an SFP port? What type of SFP module are you using? What technology of NBN is it, FTTH, FTTN, FTTC etc?
Thanks, @joegoldman . I am using SFP ethernet because the hex poe only has five ports. In order to prevent extending a switch, I just utilize this SFP port. I use a Gigamon SFP-501 1000Base-T RJ45 module (It shows FINISAR CORP FCLF-8520-3-GM in routeros) that I have. May not 100% compatible with Mikrotik as I have to set auto-neg off to make it work.
This SFP module connects to NBN Connection Box (ARRIS CM8200) via a CAT5e cable. The NBN technology is HFC (Hybrid Fibre Coaxial).
Within DHCP handshakes, the DHCP DISCOVER sends broadcast to 0.0.0.0/0 to get a IP, this process requires an interface down/up, right?
The DHCP REQUEST is sent during renew phase, it will be sent to current default gateway IP address for IP renew, not a 0.0.0.0/0 broadcast. I also noticed the DHCP server on ISP side is out of current default gateway scope. I am not sure how ISP handling DHCP renew and how they configure bootp helper across all those IP scopes.
I will also try to swap the WAN interface to a normal port instead of SFP to rule out unlikely physical issue.
@Zacharias, the IP I got is something like, 60.227.158.xx. Netmask is 17. Gateway 18.104.22.168. DHCP server is something like 56.xxx.xxx.xx (I cannot remember).
And surprise to find that IPv6 address is not changing even IPv4 is changing and dropping out. (I haven't enable IPv6 on Mikrotik router, but using ISP provider modem these days to see any difference)