Mobile Internet with 4G router: problems with IP - Page 1
Forum section: electronics / general

author: Bicurico
author_rank: Super Contributor
timestamp: August 06, 2022, 09:56:06 pm
content: Hi,I have a SIM card for 4G internet access at my secondary residence, which I use in my 4G router (Huawei). Everything was working fine, but the provider (NOS) must have had a noticable increase in traffic over the last months, so I changed the SIM card with one of the competition (Vodafone). These are pre-paid cards, costing 30 Euro for 30 days. I know there are cheaper deals, but they come with a 2 year fidelity contract, which I am not interested in, because I expect fiber to be available in some not so far away future.So my problem is that with the new Vodafone SIM, ocasionally, the internet does not work. I know that because all the surveilance cameras get offline. After 2-3 days, they become active again, without any intervention.Today I was there when it happend. Unfortunately I did not have much time, but what I discovered is that the router changed the DHCP settings from 192.168.3.X to 192.168.4.X! Also, it seems that the WAN I got assigned is actually from 192.168.3.X subnet. This explains why the DHCP server started to hand out IP's in a different subnet than the one I originally configured.Is this even possible? I know that mobile internet providers use NAT instead of giving an individual IP address, but can they be using private IP addresses instead of public ones?I think that this is what renders my network useless: because I am using mainly fixed IP addresses (settop boxes, access points, etc.), if the router/gateway is in a different subnet, nothing works.Also, I think it gets back to normal after a few days, when the lease of the WAN IP terminates and I get assigned a WAN IP in the a different range, which causes the router to switch the DHCP server back to giving out 192.168.3.X addresses, as it should.But this is weird: how does the router "remember" the former IP settings? And how does it adjust the settings automatically?Any ideas on what is going on? I don't want to have to reconfigure all devices in my network and I have no guarantees that Vodafone is not using any other subnet within 192.168.X.X.Thanks,Vitor

author: retiredfeline
author_rank: Frequent Contributor
timestamp: August 07, 2022, 12:22:22 am
content: Quote from: Bicurico on August 06, 2022, 09:56:06 pmYes, it's done. I just turned off WiFi on my mobile and used 4G mobile, and I've got a 10.x.y.z address. Nothing says that a mobile provider has to give you a public IP. Vodafone use of the 192.168.x.y range is risking collision with routers, but then maybe they didn't expect people to use routers, unlike fixed broadband.

author: Bicurico
author_rank: Super Contributor
timestamp: August 08, 2022, 07:54:51 pm
content: After spending some time with the 4G router, I ended up doing a factory reset. After reconfiguring everything, my network and the internet access seem to work normally again.In the end I did not fully understand what caused this reoccurring issue. I just hope it won't happen again.And yes, Vodafone is also using a 10.x.x.x IP for 4G, so I must have had some other weird issue.Regards,Vitor

author: rob77
author_rank: Super Contributor
timestamp: August 08, 2022, 09:24:02 pm
content: there are 3 prefixes for local networks..10.0.0.0/8172.16.0.0/12192.168.0.0/16most commonly used are the 192.168/16 and 10/8 , just use something from 172.16/12 and you'll be fine

author: AndyBeez
author_rank: Frequent Contributor
timestamp: August 08, 2022, 09:37:47 pm
content: Not convinced... I would assume the class C 192.168.n.n/16 network is defined by the DHCP server on your router. The 4G link is the gateway address - which is often a class A or B range on 4G masts. I suspect some other glitch. Insure the DHCP server on the router is nailed down (fixed) to 192.168.3.n/24 - That's subnet 255.255.255.0I should add, make sure all devices on your LAN get IP their from the router's DHCP server and, their own onboard DHCP servers are disabled. A possible conflict can occur when there are two DHCP servers on the same LAN - the router might get an IP from the rogue DHCP server!

author: rob77
author_rank: Super Contributor
timestamp: August 08, 2022, 09:57:09 pm
content: Quote from: AndyBeez on August 08, 2022, 09:37:47 pmas i understand the issue:he has 192.168.3/24 on his LAN side , his cameras are set to static IP... his ISP gives him a WAN IP from 192.168.3 and his router to avoid conflict is changing it's LAN IP and it's DHCP server pool to 192.168.4/24... when it happens his IP cameras with static IP configured will stop working... once the WAN dhcp lease expires and he gets a WAN IP different from 192.168.3.x his router resumes operation as normal.re-IP the LAN segment to something from 172.16/12 would do the trick (use something randomly from the upper half to lower the chance of conflicte.g. 172.27.136.0/24 or whatever else

author: AndyBeez
author_rank: Frequent Contributor
timestamp: August 08, 2022, 10:15:33 pm
content: Set the cameras to get their IP address from the DHCP server on the router. Use address reservation on the router to give the cameras 'fixed' IP addresseseseses. And make the router static IP if that's possible with this bizzare setup?Is there a WAN gateway address?

author: Bicurico
author_rank: Super Contributor
timestamp: August 09, 2022, 08:08:33 pm
content: Quote from: rob77 on August 08, 2022, 09:57:09 pmThat is more or less it, or at least it is what I thought: that the router automatically changed it's LAN IP to 192.168.4.x and the DHCP server as well.However, after resetting the router and reconfiguring it, I checked and the WAN IP is 10.x.x.x. So I guess that was not the case.I am not sure what happend, it could have been the IP provider, a FW bug, someone hacking the router (I doubt that, because the provider uses NAT and there is no external access to the router).While the cameras are using DHCP assigned IP's, I have several routers in AP mode, which use static IP's. Also, there are two E2 receivers with static IP's. I don't want to change those IP's to some other range and I believe that I have not done anything wrong: I am using private IP ranges.Anyway, since I don't know what happend and it is currently working as supposed, I will wait if this happens again for further action. The action might consist in changing to the provider I was using before: that one worked fine for 2 years. I only changed the provider, because download speeds were getting ridiculously low, probably due to increasing demand of the local cell.Thanks,Vitor

author: madires
author_rank: Super Contributor
timestamp: August 12, 2022, 01:01:43 pm
content: Sounds like a classic prefix clash. And it would be avoidable if Vodafone would use 100.64.0.0/10 which is a shared IPv4 address space especially for CGNAT (https://en.wikipedia.org/wiki/IPv4_shared_address_space). They are not the only one not doing their homework.

author: SiliconWizard
author_rank: Super Contributor
timestamp: August 12, 2022, 06:24:48 pm
content: Most of those 4G "routers" suck. Unfortunately.