I am using mikrotik hex poe on 6.45.6.
WAN connects to Telstra NBN. It used to work perfectly on Telstra Cable. But seems like Telstra NBN using a different way doing DHCP server.
Mikrotik DHCP client get dhcp release for 1 hour. In the middle of that hour if not get ACK, after dhcp lease timeout, the Internet will drop. See below log.

16:14:30 interface,info sfp1-wan link down
16:14:30 dhcp,info dhcp-client on sfp1-wan lost IP address xx.xx.xxx.xx - lease stopped locally
16:14:38 interface,info sfp1-wan link up (speed 1G, full duplex)
16:14:40 interface,info sfp1-wan link down
16:14:46 interface,info sfp1-wan link up (speed 1G, full duplex)
16:15:35 dhcp,info dhcp-client on sfp1-wan got IP address xxx.xxx.xx.xx

It takes a while to detect that WAN lost the IP and cycle the interface to force a DHCP rebind. The whole process will get home internet down around 5-10 minutes. But it will happen every hour. Sometimes, no drop out the full day. But sometimes, happens every hour.

To isolate the problem, I also took out Telstra provided NBN compatible smart modem to get the DHCP IP address. And mikrotik router sit behind it. Surprisedly, The Telstra Modem DHCP renew works without any issue. It got 1 hour DHCP lease at the beginning, then after 35 mins, it will extend its DHCP lease to 1 day. So I don't understand why Mikrotik DHCP cannot act the same way.

I searched a lot threads who using Cisco device had similar issue with NBN DHCP drop out, and ended with Cisco IOS upgrade.
Not sure is this something that Mikrotik can help to make DHCP client compatible with NBN DHCP server? Or at least provide some customised option to make it work. Happy to provide supout.rif if anyone can help troubleshoot the issue. Thanks in advance.

I may expect Mikrotik will say that ISP DHCP server is not following RFC standard.
But check this thread. https://forums.whirlpool.net.au/archive/2654421
Issue seems get solved from various router vendor like ASUS, Cisco by upgrading firmware.
Anyone experienced similar issue? Thanks a lot.

Can I confirm the spf interface down is caused by DHCP client not able to renew the lease in order to perform a DHCP full discover OR the spf interface speed negotiation issue that brings down the link then cause DHCP lose the IP?
I just trying to understand whether it is a DHCP client issue or maybe physical connectivity issue. Thanks.

Remove the DHCP client from MikroTik and assign a static IP instead... as simple as that...!

Remove the DHCP client from MikroTik and assign a static IP instead... as simple as that...!

it's impossible to hard code a static public ip to WAN interface. once the DHCP lease expires, the ip will be recycled and assign to other users.
Even if i request static ip address from ISP, the static ip is also delivered thru DHCP.

Even if i request static ip address from ISP, the static ip is also delivered thru DHCP.

No...!
Ofcorse you can assign that static IP to an interface without the need of a dhcp client...

Also, are you sure the IP given to you by your ISPs router through DHCP is a Public IP address?

Even if i request static ip address from ISP, the static ip is also delivered thru DHCP.

No...!
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?

Am totally sure for what i write...
If you are assigned a static IP, YES you can use it statically to your Interface and then configure your routes, NAT etc...

Besides that, you said your IP is provided through a DHCP server, you gave no more details...

If your IP is given through a tunnel, which you NEVER said that before, contact your provider to see what type of tunnel that is and if it can be configured on the MikroTik... for example if it is a PPPoE client, yes you can configure it on the MikroTik side as long as you have the username and password...

Am still not sure if you are given a real Public IP or no...

Even if i request static ip address from ISP, the static ip is also delivered thru DHCP.

No...!
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 60.227.255.254. 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)

Just an update.
My ISP provided me an addon feature which is static IP address. Though the static IP is still delivered thru DHCP and needs renew every 4 hours. I haven't tried hardcode this IP to WAN interface manually cause I believe it needs to be registered on ISP's DHCP server for the traffic flow.
However, this static IP solves my Internet drop out issue. Even each 4 hours static IP DHCP renew does not trigger any drop.

I admit I have not checked in a while under DHCP client, as 99% of RBs I manage have static IPs and not using debconf, but I recall a while back the default config was without any setting for ether1 under DHCP client.
Any clue when this default changed?
Or maybe I was just not paying attention and it was always there?

Hi

I too am facing this issue. Maybe theres a script someone has made to check internet connectivity every x mins, if no internet renew DHCP client lease?
To get my internet back I just have to renew the lease.

woah! found it ! EDIT: this works better... substitute interface names with your own
:if ( [/ping 8.8.8.8 interface=ether1-wan count=6 ] = 0 ) do={/ip dhcp-client renew [find interface=ether1-wan]}



tested working :-)
cheers