At my wits end - something going wrong with DHCP on Virgin Media

podgeandrodge

Long story short, have a new router and rebooted it (trying to fix a separate problem) and lost internet access. It's now disconnected and wifi re-enabled on Virgin Media box (in router mode which was working fine with wifi disabled).

Now, I have access on some devices. But not on others. Example - an internet radio keeps giving "network timeout" and dhcp errors. So I went into Hub 2.0 and looked at DHCP lease time (not that I have a clue) and it was 24 hours (86400). I changed that to 2 minutes (120) and the internet radio immediately came on. Switched it back to 86400 and timeout again immediately.

I haven't a clue what is going on, but I suspect that DHCP issues from the Virgin Hub are probably causing the fact that my router and radios etc. are all very confused.

Any suggestions? Can a 2 minute DHCP lease cause other issues, and if I revert to 24 hours, and turn the modem off, will everything unlease itself and go back to normal. Thanks!

smuggler.ie

There should be only one device serving DHCP on the network at any given time.
IP's issued on "first come" basis in sequence from low to high(this does not apply to devices with static/reservation)


How many network devices you have?
What is your DHCP pool? i.e. 192.168.1.50-192.168.1.100 only allow 51 devices to get IP's dynamically - if 52nd device request IP it will get denied/error

DHCP lease time define how long the IP will be assigned for device(by MAC) - in normal conditions this should not have effect on devices as they can obtain new IP if needed from pool available.
It might become relevant if you exceeding or near limit of IP availability - IP's that are no longer actively in use would be released to new devices after lease term expired.

podgeandrodge

Probably 10 network devices so not too high.

The router (before the problems occurred) had used 192.168.50.1 and the hub 2.0 was still on 192.168.1.0.

I assumed that was fine as the router was completely separate to the hub for providing wifi. It certainly worked fine for days until I did something wrong yesterday and rebooted the router.

Now the hub says everything fine, and it just seems to be the 1 internet radio that won't connect unless the dhcp lease time is 2 minutes.

I'll try again today from scratch maybe, remove all devices from router (they're nearly all on a switch anyway) and maybe try the router again, as it's wifi was far superior.

PS I was in router mode in the VM Hub, would modem mode be safer bet?

Thanks.

smuggler.ie

What is "new" router make/model

With this minimal device count and default IP range lease time should not have impact , unless some fault on router. Having lease on short term is fine, your devices will be renewing more frequent, but 2 min sounds ridiculous.
You can set your radio on reservation(specific IP assigned to device on router, permanently*) and see if it helps, but i dont think that is the problem here.

Does your "new" router have split WiFi (2.4 and 5 GHz separated), does hub2.0 have same? - commonly they combined on ISP routers and certain devices cannot operate on 5GHz, which is prioritized, or range to short to provide coverage. See if there is option to split WiFi and if radio work on 2.4

If you use both devices(routers) with DHCP enabled then you have double NAT - can do, but…. if you have to share some resources on the network ( printer, NAS, DLNA, other) you might have issues as devices might be on different LAN's(WLAN's)

Modem mode disables NAT, DHCP, firewall and some other functions. WiFi might remain, but should be disabled/not used as there will be no firewall and where would devices get IP?

podgeandrodge

Thanks Smuggler. I am what they meant by "a little knowledge is a dangerous thing" here.

Router is an Asus AX52 purchased last week.

Originally, when I set it up, the Virgin Media Hub was in Router Mode, but I disabled the 2.4 and 5ghz wifi. The Virgin Hub was accessible (and still is) on 192.168.0.1 . The setup page for the Hub (which currently has the 2 minute DHCP lease due to my change) shows "starting local address" of 192.168.0.10. I have never used Modem mode to date.

I then initially had the AX52 in Router Mode and as far as I recall, the ip address assigned was 192.168.50.1, before changing it to AP mode (for some reason that I don't recall) and it all worked fine either way.

I think I messed up the Asus app at some point when I was trying to figure out why a mobile phone wouldn't connect to the wifi (it turned out that it was because it was Wifi6 that the phone couldn't connect to), and at that stage the damage was done as all the problems began.

The router is completely removed from the equation now as I try to figure things out. But the internet timeout persists, albeit I think it's only on 1 device now, the internet radio.

Re. your question on "where would devices get IP" - I had assumed when the Asus Router was in AP mode that it would assign the IP addresses? Or only in Router mode?

Re. your question on bands - the Virgin Media Hub has both bands separated (and currently re-enabled as the Asus is out of the equation). The Asus had an option to combine, or separate - and when it was working, I had them as 2 separate bands as I had a concern that some legacy devices might be 2.4 only.

Your point on "both devices(routers) with DHCP enabled then you have double NAT " sounds like it could be an issue here, and I'm not sure how I set it up but will re-assess!

Thanks!

smuggler.ie

Cant say for certain, check if VM allow you to run hub in "modem" mode only. Then you could have Asus acting as router with all "nice" features it can provide.

If you using VM as router, then Asus should be in AP mode(DHCP and some other features disabled and IP comes from VM hub) and it should get required metrics automagically. However, it will disable other "handy" features along

When you enable Access Point mode on your ASUS router, it effectively disables its routing capabilities, transforming it into a device that extends your existing network's wireless coverage. This means that the Access Point's IP address is assigned by the parent router

Regardless what way you proceed, i recommend to have Asus on dedicated IP for future management/config:
1.Disconnect Asus from network»
2.Set reservation on VM hub for Asus MAC address to assign 192.168.0.250(or other high last_octet number)(note - once you give this IP to one device it cannot be assigned to any other device)
3.Reset Asus to factory defaults»connect laptop/PC/app directly to it»configure for AP mode.
4.Connect Asus to VM network - check if Asus appear with IP as it should, connect and complete required config(WiFi, etc). Once happy with config»backup config to file (should be option under "Administration", helps if you need reset/restore in the future)

Note: accessing Asus(or any other network device for that matter) through IP on PC display more consistent and better view of controls than any Fu!"£$% app, personal view on this nonsense

If you manage to get VM into modem only mode, Asus will have to be reconfigured. search boards(elsewhere), perhaps someone have done it and have details

Some network devices might need restart to obtain network metrics - restart radio, if it takes - "forget" WiFi and reconnect again.

See if it helps

podgeandrodge

https://www.boards.ie/discussion/comment/122369194#Comment_122369194

……..Edit:

@smuggler.ie

Ok, thanks for your help on this. As I actually had port forwarding for CCTV on my Hub, and ALSO 2 ethernet cables from the VM Hub running over my roof to provide wired access in 2 rooms, I didn't want to go into Modem Mode - as my understanding is that this would stop those LAN ports working.

So…I figured out what you meant by assigning the Asus MAC address which I found on the back of the Asus, and did that assigining to 192.168.0.250. That's handy - as I can know that this is always going to be the login page for the Asus on my pc.

I then disabled WIFI on the VM Hub, re-setup the Asus which automatically went into Router Mode, but then changed that to AP mode and bingo, all looks ok.

I'm not sure if I'm technically in this "double nat" thing but seems grand.

Thanks again for your assistance.

And also - the Asus Router even in AP mode is providing more information on even my WIRED devices to the VM Hub - such as giving me the actual device names for things like CCTV which the VM Hub simply called "unknown device" - that is helpful!

smuggler.ie

did your radio came back alive ?
Glad if it worked

podgeandrodge

https://www.boards.ie/discussion/comment/122371456#Comment_122371456

Haha yes and not a buffering or network timeout in sight!

(Am I in a double Nat situation from what I described?l

smuggler.ie

NAT (Network Address Translation)
Double NAT when your device IP has to be translated twice. Translation does take time, even if its ms, still time
Your VM hub creates 192.168.0. network and all devices connected to it get IP's in that range 192.168.0.2, 192.168.0.3….192.168.0.250..
If your Asus set on 192.168.0.250(WAN side) would have DHCP on its own it would create network on LAN side as 192.168.50. and all devices connected to Asus would be 192.168.50.2, .50.3, … , .50.150… etc
this would mean that radio connected to Asus on IP 192.168.50.5 , to get internet, packets are translated to network 192.168.0. first, then goes out and on return to 192.168.0. have to be translated again to 192.168.50. and finally delivered to 192.168.50.5 device.

Connect laptop directly to Asus - what IP your laptop get? Preferred scenario is that IP is on 192.168.0. network and this indicate that VM hub is serving DHCP - no double NAT

podgeandrodge

Ok, I had a laptop and connected to the Asus wifi and it's got itsle a 192.168.0.126 address so coming from the VM Hub is my understanding. (Asus Router used to have the 192.168.50.1 ip until i set it to the 192.168.0.250).

The Asus app shows wired devices on the network wired to the VM Hub too and all devices are 192.168.0.xxx

Thanks.