LG aircon refusing to connect to WiFi

[Adam_S]

Hi All,

Need some expertise with LG aircon. It suddenly disconnected from my wireless network, and refuses to reconnect (no changes were made). Occasionally it would reconnect and immediately drop off. I tested on a standard home router wireless with no security, it still refused to connect. LG have since replaced the wireless dongle and all the circuit boards. It now connects to a the home router WiFi and a phone hotspot, but still refused to connect to my WiFi. Upon further investigation i can see that it obtains an IP address and the translation table shows that it communicating to DNS 8.8.8.8 as primary (which is correct), but has a secondary of 9.9.9.9 (i have not specified this anywhere), additionally all other devices on the SSID are connecting fine. I have attached the device config and some outputs.

[JPavonM]

Have you tried to enable ONLY one set of basic rates and only support the rest of them? (the DSS ones 1- and 2-Mbps) (OR the OFDM ones 6-, 12 and 24-Mbps)

Some time ago I found some IoT sensors that were unable to connect as they were only expecting basic rates (I saw this in the association request packet sent from them), and as far as I did that, they connected straight away.

[Adam_S]

The SSID it associates to is limited to wireless G speed, OFDM 54mbps and
below. The initial association seems to work as its only the final stage
where it drops out, as I can see that MAC address is learned and IP address
provided (from DHCP) and even gets as far as making an ARP entry, then the
app stalls, and the packet cap seems to show a bunch of TCP
retransmissions(i have a suspicion that an ACK maybe getting lost
sonewhere), and then it just gives up and disassociated itself.

[Scott Fella]

You have provided more info that does help.  It seems like the wireless portion is fine because your device can associate and authenticate along with getting an ip address.  Traffic then is bridged to your switch that the ap is connected to.  When you are using a home router and that works, you are double natting.  Is there a way to just bridge that traffic to do more testing. What is doing the NAT to your ISP, nothing changed over there?  Have you tried to reach out to the LG community to see if anyone is experiencing issues also?

[Adam_S]

Havent tried the LG community yet. Issues seems to be pointing to the
router, as mentioned previously, I've connected the RSP router directly to
3845 and attempt to use as an access point bypassing the cisco APs and it
does the same thing. If I connect it back between the 3845 and the RSP
handoff, no issues.

[Scott Fella]

Sorry, but really can't follow but I'm going to guess here.... RSP, is that the ISP router and is that is connected to the 3845, if so, you are double natting which might be why it's breaking.  Have you tried not using the ISP router and connecting it straight to your 3845 or that can't happen due to your ISP? I can have my ISP either route or bridge, I prefer bridging so that my router can do its thing.  Now when I have the ISP doing the routing, then I have to port forward some traffic or else it just breaks.  Might not happen for all applications, but something to take a look at.

[Adam_S]

Fair enough.

Cisco 3845 is connected directly to internet, via gig 0/1 and is doing nat
(not using the ISP modem)

If i plug the ISP modem into the switch and just use it as a AP (by passing
the cisco access points) the aircon still won't connect.

3845 -> internet
I
Switch
I
Modem (wireless) -> aircon

If I use the ISP modem to connect to the internet. Aircon can connects via
ISP modem no issues.

3845 -> modem -> internet
I
Aircon

Hope that's a bit clearer.

[Scott Fella]

I would think you need to have the ISP modem in order to pass any traffic to the ISP.  The ISP would not support connecting direct to a router if they provided you with a modem.  Really should be something like this.

LG Aircon ~~> AP ~~> 3845 ~~> ISP modem 

[Scott Fella]

How I have mine and it is typical design. I have my xFI modem in bridged mode so no nat.  I have a Meraki MX that does the routing and nat. Connected to that and from the MX, I have multiple switches that are trunked.  I then have access points connected to the various switches I have.

[Adam_S]

That does work too, but AC still fails to connect with same results. If I
connect the AC to ISP modem in that configuration will work fine.

[Rich R]

If I have understood all the discussion correctly then it sounds like the conclusion is that the problem arises when the 3845 is doing the internet NAT.
That suggests a few possible problems:
- NAT ALGs disrupting the traffic - you can try disabling ALGs
- NAT fragment re-assembly causing problems - check the ip virtual-reassembly command (VFR feature)
- Software bug in IOS NAT causing packet corruption (there've been a few of those over the years)

[Adam_S]

Yes. I have been suspecting a possible NAT issue. The NAT ACL has the
permit IP any any, permit tcp any any, permit udp any any statements and
was working previously along with the same IOS version. I also tried
disabling the TCP timestamps. I havent looked at the virtual reassembly
though.

[Rich R]

https://www.cisco.com/c/en/us/support/docs/ip/network-address-translation-nat/13772-12.html
Use of permit ip any any is specifically not recommended with NAT:
"Note: Cisco highly recommends that you do not configure access lists referenced by NAT commands with permit any. If you use permit any in NAT, it consumes too many router resources which can cause network problems."

And you still haven't checked the effect of the ALGs.