Conflicting DHCP when Deco in AP mode ?
Today I ran into an issue which made me almost cringe.. as I hadn't expect this to happen, considering I've been working in the IT networking business for over 30 years..
I had recently purchased a Deco M5 mesh set with 3 nodes and setup as AP access points, because I alread have a decent router from my ISP (Zyxel EMG2926). This has been working fine for the last 6-8 weeks and nothing to complain about.
Last night, for some strange reason my router rebooted and I lost Internet connexion from everywhere, including my wired PC's which I use every day to work from home.. So getting back internet was critical to me and I tried the quick obvious options like rebooting the router and also reseting to factory the router, then reloading the configuration I had on backup.. To no avail, I wasn't able to get an functional internet, still the router diagnostic was able to ping any IP address outside my network.. Since I needed to work and support clients, I disconnected the Zyxel router and put back the Mercku M2 Hive base I had prior to the ISP router and after 5 minutes, was back into business.. (The Mercku is also a Mesh Wi-Fi system with 4 Bee nodes, albeit it wasn't working to my entire satisfaction, thus the purchase of the Deco M5).
Having spend the morning with work, I had hope the issue with the router might have been on the ISP side, so tried to set it back in action. Result was identical and nothing was really working.. Put the Mercku M2 back for the PM as I had a support call and did need internet ASAP.
At the end of the PM I got back to my router and it was so weird that I even tried to reset the Zyxel for the n-th time and start from scratch.. What puzzled me was that it was working if I forced my computer into fixed IP address, and even with DHCP Mac address reservation, the router wouldn't route my requests properly to the internet.. Looking at the IP addresses in the config made me think that router was totaly corrupt and crazy.. The router's IP is 192.168.127.1, but returns 192.168.127.102 as gateway and .254 for the DNS server, which is even crazier.. This is when I started to scan my network for rogue devices with my Android smartphone, but couldn't find anything suspicious. I've a lot of IoT devices and aside of the 3 Deco M5 AP's, there was nothing un-usual. However, the .102 IP address made me tick and look closer at the Mac Address, to finally discover that the main Deco M5 unit (the one connected by Cat5 cable to the switch) was the culprit.
For some obscure reasons my Zyxel router was thinking that the Deco M5 AP unit was the master DHCP on the network, despite TP-Link saying in their documentation that it is not the case when in AP mode.. As a proof, my Mercku M2 router had no issues at all with that and was perfectly handing over IP addresses to all devices..
Has anyone run into such a situation with another HW router ? getting conflicting DHCP server mode while the Deco M5 is in AP mode ?
I fixed my problem my disconnecting the Cat 5 cable temporarly from the switch, rebooted the Zyxel router and voilà.. after it was back as 'master' DHCP, I plugged the Deco M5 back and all was working as before.. But I'm really curious about that strange behavior.
Any comments are welcome on this.
- Copy Link
- Subscribe
- Bookmark
- Report Inappropriate Content
@GPGeek same issues here with M5 deco's!
After turning on to AP mode the master deco gives dhcp addresses on the cabled and wireless network. IP lease with the gateway- and dns address of this master deco to the clients.
Rebooting is also not helping this out.
I have to turn back in Router mode otherwise my clients want get internet access because the Master Deco is not the gateway in my setup.
FIX this please it takes too long to solve this issue.
- Copy Link
- Report Inappropriate Content
Thought it was worth adding to this thread that I've had this issue a couple of times now on my Deco S4 in AP mode. (hence I've been looking for information on this forum)
In my case the S4 spontaneously started handing out DHCP leases (which were wrong of course, because it cannot be configured in AP mode) and broke every DHCP client in my network. I'm 99% sure that there were no issues with my actual DHCP server (a Ubiquity edgerouter) at that time.
There are a number of threads on the forum about this and i'm shocked that anyone in TPlink though this was a good idea, let alone attempt to justify it. For the avoidance of any doubt rogue DHCP services break networks and the Deco units would be thrown off of any corporate network for that alone.
Is there any update on this fault and it's solution?
- Copy Link
- Report Inappropriate Content
Of course there isn't an update. They honestly don't care about this at all.
Ditch the product and ditch the vendor.
- Copy Link
- Report Inappropriate Content
Dear TP-Link team,
as I am suffering from exactly the same problem (rogue DHCP issues with multiple wired Deco units and Zyxel modem), I would like to suggest another idea that may be easier to implement on your side.
First of all, it seems the DHCP issue is triggered by particular Zyxel modems / firmware versions. In my case, while using my old ZTE modem, there were no issues whatsoever (confirmed by other contributors as well). My current Zyxel modem is VMG8825-T50, firmware version V5.50(ABOM.4)b4_D0. The issue occurs only when the slave Deco is wired to Zyxel modem (Ethernet backhaul). In case of WiFi backhaul of the slave Deco, there is no issue whatsoever.
Obviously, Zyxel modem VMG8825-T50 exhibits some networking pattern (legitimate or not) that triggers the undesired DHCP action on Deco side. As a potential remedy, you can investigate the networking pattern of Zyxel and try to mitigate that on Deco side (i.e. make Deco less sensitive to Zyxel's networking pattern). Using this approach, you can resolve the issue while keeping your intelligent DHCP feature intact.
I hope that helps.
Best regards,
Igor
- Copy Link
- Report Inappropriate Content
They won't do a thing. Plus this isn't limited to Zyxel modems. It happens to lots of people with different hardware.
The whole design is crap. I repeat, they won't do a thing, you're stuck with this junk.
- Copy Link
- Report Inappropriate Content
Well, the whole discussion seems to be centered on disabling the DHCP server feature in AP mode, whereas an alternative solution (making the design less sensitive to external (modem-induced) network blips) was not considered at all, so I decided to bring it forward. Whether TP-Link is going to address the issue in one or another way, is a separate question.
- Copy Link
- Report Inappropriate Content
The thread is 2 years old.
Making it less sensitive won't change the fact it's a fundamentally flawed design to throw up a DHCP server on a network and dish out IPs in range that 1) the user has no control over 2) IPs from a different broadcast domain.
It will do nothing but break your network.
- Copy Link
- Report Inappropriate Content
I don't disagree, but I've recently realised that the IP range that the Decos fall back to is NOT totally out of your control. They seem to fall back on whatever range you used in the Decos the last time they were in Router mode.
I'm currently experimenting with using the same IP range on my Decos as I use on my ISP router, reserving the same IP addresses for the same "difficult" devices on both the Decos and ISP router, before finally switching the Decos back to AP mode.
It seems to me that under the circumstances where the ISP router goes offline, the Deco's will then just provide the same address details to every device, and in theory that should work around the problem.
- Copy Link
- Report Inappropriate Content
- Copy Link
- Report Inappropriate Content
I bought tplink deco E4 and i searched on forum and I knew about issue " Smart DHCP". It is a big issue. I use DHCP on Windows server and relay to it from router. When reboot or can not connect to router, Deco E4 will automatically provide DHCP to user. But as Kevin say when main DHCP server came back, it will stop DHCP from Deco E4 but I did not see about this. User still get IP from Deco . I don't know any solution to fix it. It still cause a serious issue in my company to challenge me to fix it. Please for me solution to fix it soon. Thanks
Note: I use AP mode of Deco E4. And 80.148 la IP of AP Deco.
- Copy Link
- Report Inappropriate Content
Information
Helpful: 8
Views: 46483
Replies: 151