CGNM-3552 wifi to lan issue

Need Help?

That's what we're here for! The goal of the Rogers Community is to help you find answers on everything Rogers. Can't find what you're looking for? Just ask!
cancel
Showing results for 
Search instead for 
Did you mean: 
Reply
Loux
I Plan to Stick Around
Posts: 16

CGNM-3552 wifi to lan issue

Hi,

I can't establish a TCP connection (ssh, http, ...) from devices on the Wifi (Android, ubuntu) to devices on the LAN (Ubuntu). It seems to be linked to an arp issue ? If i add the arp entry of the LAN device on the Wifi device, I'm able to connect.

Anyone else has issue this issue ?

 

Louis

modem : CGNM-3552

Firmware 4.5.8.22 (same issue with 4.5.8.21)

Security Firewall : level Minimum, Ping from WAN Allow

 

***EDITED LABELS***

Solved! Go to Solution.

Accepted Solutions
Loux
I Plan to Stick Around
Posts: 16

Re: CGNM-3552 wifi to lan issue

Hi @RogersDave , @RogersShaun

i found it ! If my PC server on the LAN is using the modem dhcp with a static address provided by the rogers modem outside of the range (ex: let's says 192.168.0.2 while the dhcp range is 192.168.0.10-200) then there will be an ARP issue with devices connected on the Wifi trying to talk to the LAN.

Regards,

Louis

View solution in original post


All Replies
RogersCorey
Moderator
Moderator
Posts: 1,430

Re: CGNM-3552 wifi to lan issue

Hi @Loux!

 

Welcome to our Community Forums!

 

I personally don't have a lot of experience with Ubuntu and that OS does fall outside of our regular scope of support.

 

Perhaps another Community member has encountered this issue and could share some insight? 

 

Regards,

RogersCorey

 

 

 

Loux
I Plan to Stick Around
Posts: 16

Re: CGNM-3552 wifi to lan issue

Hi,

let me rephrase, am I the only one having issue trying to connect from a Wifi device to a LAN device on the same network with the CGNM-3552 modem ?

Regards,

Louis

Gdkitty
Resident Expert
Resident Expert
Posts: 14,300

Re: CGNM-3552 wifi to lan issue

It isnt specifically something that i have heard from other users, at least on here.



Loux
I Plan to Stick Around
Posts: 16

Re: CGNM-3552 wifi to lan issue

Hi,

from the Wifi Device, if i query the port 80 of the lan device, i don't even see the tcp pkt coming with tcpdump (on the lan device).

 

Regards,

Louis

RogersCorey
Moderator
Moderator
Posts: 1,430

Re: CGNM-3552 wifi to lan issue

Hi @Loux!

 

As far as I'm aware, this port is reserved on residential connections. If you're looking to host a server, you may need to look into getting a business Internet account or attempt to specify an alternate port.

 

Regards,

RogersCorey

Loux
I Plan to Stick Around
Posts: 16

Re: CGNM-3552 wifi to lan issue

@RogersCorey, you don't seem to understand. I'm not trying to do anything with the outside world (called port forwarding or NAT).

I'm talking about communication (TCP to be precise) between my inside/private Wifi network (from the rogers modem) to my inside/private LAN network (from the rogers modem). All the equipments are on the same IP network 192.168.0.0/24.

 

There is an issue with ARP

 

Regards,

Louis

RogersDave
Retired Support
Retired Support
Posts: 611

Re: CGNM-3552 wifi to lan issue

Loux,

 

I looked at your issue and I don't think there is a modem problem. If ARP was broken between WiFi to LAN (internally these are 2 distinct interfaces bridged together), it would have an impact to many users given the fact that it would break everybody trying to use any wired device from WiFi (NAS, printer, media streaming).

 

That being said, I am sure you do have an issue so let's try to figure it out and let's start with the root cause of why your WiFi device is not getting responses. A couple of starter questions:

 

1. On your WiFi device ARP table, do you have an entry for the gateway (192.168.0.1)?

2. On your LAN device ARP table, do you have an entry for the gateway (192.168.0.1)?

3. Are you using DHCP on all devices (both the LAN and the WiFi)?

4. Did you change the LAN subnet on the gateway?

 

And the most important one...

5. Can you confirm that all devices have the same subnet mask, especially if not using DHCP on a device?

 

Based on my experience, ARP issues are caused 90% of the time by an incorrect subnet mask. Other 10% is a firewall (software or hardware) is blocking communication (Windows public mode for example). I've also seen, very rarely but seen it, a device on the network acting as a honey pot and trying to hijack ARP responses to intercept traffic.

 

Dave

Loux
I Plan to Stick Around
Posts: 16

Re: CGNM-3552 wifi to lan issue

Hi,

all devices are on the same network, they are all connected to the rogers modem and use dhcp, they are all on 192.168.0.0/24 with a netmask of 255.255.255.0.

It is hard to see the arp table of the android device (connected with Wifi).

But with my laptop, connected on the wifi, if i replace the arp entry of the PC (connected on LAN) i can reach him (ssh connection). With the default arp entry provided by the rogers modem, i've got connection refused.

 

Regards,

Louis

RogersShaun
Moderator
Moderator
Posts: 319

Re: CGNM-3552 wifi to lan issue

Hi @Loux,

 

@RogersDave might not have seen your response.  Just a friendly reminder to use the @ symbol, then type or click on a username when replying to someone if you'd like them to get notified of your response. 

 

Have a great one!

RogersShaun