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Zzoomm DHCP Renewal - Fritz! Router

Mot

Casual Member
Fairly niche question - I'm seeing my DHCP lease renewed every 30 minutes and get a DHCPv4 NAK (not acknowledged) message in the log. This causes the connection to be refreshed which takes ~3 seconds and affects VOIP, VPN and DoT DNS.

Zzoomm have been great and confirmed their leases are just over 8 hour and it's my router requesting renewal, rather than anything their end. Frtiz (AVM) just point the finger at Zzoomm.

There doesn't appear to be any configurable settings in the router for DHCP. Wondering whether anyone has come across this with other non Zzoomm issued routers? Or with any other altnet.
I don't want to move away from the Frtiz! if possible, it's features really suit my needs. I guess I could go DD WRT but wouldn't know where to start tbh.
 
Hmm that doesn't seem right. Out of interest, does this connection disruption affect devices connected via both WiFi and wired networking? I've seen issues where WiFi can be a bit flaky for such things.

Obviously, one way around this might be to forget DHCP and just do manual IP assignment, but in a busy modern home that extra admin could be too much of a ball ache.

DHCP lease renewal is a fairly normal process, but it should normally occur without you noticing. But I'd probably also check your IPv4 settings to make sure the local network's IP range under DHCP has plenty of spare address capacity and isn't too constrained.

Also, can't you set the time under home network > network > "Valid for"?
 
Hi Mark,

Sorry, I might not have been clear. This is the lease from Zzoomm for my public IP. I don't have a static IP so have to request my IP via DHCP.

Zzoomm supply an Icotera router that's really lacking in features, so no use to me.

I'm not using WiFi from my router and instead use Ubiquiti throughout the house.
 
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If you have a switch that can do port mirroring then it would be interesting to see what the DHCP params are being sent by the Zzoomm BNG
 
If you have a switch that can do port mirroring then it would be interesting to see what the DHCP params are being sent by the Zzoomm BNG
I do indeed but not sure what I’d be looking to capture - just wireshark a connection request and return?
 
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I have seen an issue similar to this several years ago on a corporate LAN where a resilient pair of DHCP servers got themselves out of sync and were fighting with each other to issue different leases to the same client, denying the lease handed out by the other server, and effectively ending up in a DHCP handbag fight. The symptom that caused this to be noticed was with clients briefly loosing their network connection as the DHCP client didn't know what to do and released the IP briefly before often picking up the same or a different IP.

You would hope that the ISP does not have the same issue, or they would have some monitoring that would highlight this, but a packet capture of all broadcast and DHCP packets would be the place to start.
 
Last edited:
Have you chucked it on the line to see if it exhibits the same behaviour as your Fritz?
I have today, and it's fine. Looks like it's an issue with the Fritz. Zzoomm say the only other instance they saw of this occuring was with another Fritz router.
Looks like I'll have to replace it.
 
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Little update for anyone that might find this page via search engine.

Zzoomm have confirmed it’s a config issue their end, and are implementing a change early next month to address it.
Their technical CS has been a joy to deal with.
 
I have had Zzoomm FTTP installed recently, and am looking to replace the supplied Icotera router with an Asus Tuf AX6000 router. Have you got any general router installation, set-up or configuration tips? Thanks.
 
It's super simple - connect the ethernet cable to the WAN port of your AX6000 and setup your ISP connection as DHCP. That it! No messing with MAC spoofing, usernames or passwords.

Zzoomm implemented the change I mentioned in my last post, and now my Frtiz router is working perfectly with no more DHCP renewal issues.
 
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