System disconnect

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lexridge
DD-WRT Guru


Joined: 07 Jun 2006
Posts: 1244
Location: WV, USA

PostPosted: Mon Feb 26, 2024 22:43    Post subject: Reply with quote
Seems like only one computer behind the router is being NAT'ed. I would try doing a factory reset and start over from scratch and make only minor and necessary changes at first.
_________________
- Linksys EA8500: I-Gateway, AP/VAP 5ghz only r56820: Features: WDS-AP, VLANs, Samba, WG, Entware
- Linksys EA8500: WDS Station x2 - r56941
- Netgear R6400v2: WAP/VAP 2.4ghz only w/VLANs over single trunk port. r56820
- Netgear R7800 (WDS-AP, WAP/VAP) - r56820: Features in use: multiple VLANs over single trunk port
- Linksys MR7350: Testing r56941
- Linksys Velop WHW03v1 x2: OpenWRT w/GRETAP tunnel for VLANs on VAPs
- OSes: Fedora 38, 9 RPis (2,3,4,5), 20 ESP8266s: Straight from Amiga to Linux in '94, never having owned a Windows PC.

- Forum member #248
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Machforr
DD-WRT Novice


Joined: 17 Feb 2024
Posts: 22

PostPosted: Tue Feb 27, 2024 13:03    Post subject: Reply with quote
I'll try, but I can't do it right away. Need interwebs for work.

Though won't a reinstall invalidate my activation? According to the website, it's be (re)activated 3 times already.

UPDATE:
I tried a 'factory default' from Administration/Factory Default and it didn't actually reset anything.
All settings were still there. As was the issue.

I REALLY don't know what setting on either system or the router makes it so that those two systems can't seem to connect normally. It works for my server, which is on another IP entirely (And disconnecting the NICs didn't do anything) and I agree with Sp1derman... I'm befuddled as to what's happening.
Sp1derman
DD-WRT User


Joined: 16 Jun 2006
Posts: 168
Location: Germany, BW

PostPosted: Tue Feb 27, 2024 17:22    Post subject: Reply with quote
at least I think there is something wrong with your Installation.

Factory default has to work, and if not it's a red flag for me.

What you can try is to change the IP of the DD-WRT box from 192.168.1.1 to lets say 192.168.5.1

Do you have any own firewall rules active?
Machforr
DD-WRT Novice


Joined: 17 Feb 2024
Posts: 22

PostPosted: Tue Feb 27, 2024 17:35    Post subject: Reply with quote
I'll give a shot at changing the IP to see if something happens.

As for the firewall, I do believe these are the default:
Sp1derman
DD-WRT User


Joined: 16 Jun 2006
Posts: 168
Location: Germany, BW

PostPosted: Tue Feb 27, 2024 17:58    Post subject: Reply with quote
Yes looks like default but I had in mind Administration/Commands and there Firewall. Did you put in any iptables rules?

Please also retry the Default settings, this really has to work.
lexridge
DD-WRT Guru


Joined: 07 Jun 2006
Posts: 1244
Location: WV, USA

PostPosted: Tue Feb 27, 2024 19:03    Post subject: Reply with quote
You really need to be looking at your dd-wrt system logs at this point. To do this you will need to enable logging. It's located in the Services tab, near the bottom under System Log. Enable both Syslogd and Klogd.

Next, for best results you need to telnet as instructed earlier into dd-wrt and type this command.
Code:

tail -f /var/log/messages

Now just watch that for a while as you are experience problems and see if any obvious errors show up.

If you are not comfortable with using telnet, you can also access the log via the WebGui under Status/Syslog, but it a bit of a pain to update.

@Sp1derman I would find it extremely unlikely he has added any iptables rules under Administration/Commands considering his self admitted level of expertise.

_________________
- Linksys EA8500: I-Gateway, AP/VAP 5ghz only r56820: Features: WDS-AP, VLANs, Samba, WG, Entware
- Linksys EA8500: WDS Station x2 - r56941
- Netgear R6400v2: WAP/VAP 2.4ghz only w/VLANs over single trunk port. r56820
- Netgear R7800 (WDS-AP, WAP/VAP) - r56820: Features in use: multiple VLANs over single trunk port
- Linksys MR7350: Testing r56941
- Linksys Velop WHW03v1 x2: OpenWRT w/GRETAP tunnel for VLANs on VAPs
- OSes: Fedora 38, 9 RPis (2,3,4,5), 20 ESP8266s: Straight from Amiga to Linux in '94, never having owned a Windows PC.

- Forum member #248
Machforr
DD-WRT Novice


Joined: 17 Feb 2024
Posts: 22

PostPosted: Tue Feb 27, 2024 20:52    Post subject: Reply with quote
@lexridge

Telnet works great, worry not. I'm used to dealing with the command prompts being from the old DOS days.

I decided to let the log run and after a while this popped up:
Code:
Feb 27 15:44:02 Machforr kern.warn kernel: [21925.456612] net_ratelimit: 32 callbacks suppressed
Feb 27 15:44:02 Machforr kern.warn kernel: [21925.456617] nf_conntrack: nf_conntrack: table full, dropping packet
Feb 27 15:44:02 Machforr kern.warn kernel: [21925.458847] nf_conntrack: nf_conntrack: table full, dropping packet
Feb 27 15:44:02 Machforr kern.warn kernel: [21925.461530] nf_conntrack: nf_conntrack: table full, dropping packet
Feb 27 15:44:02 Machforr kern.warn kernel: [21925.463004] nf_conntrack: nf_conntrack: table full, dropping packet
Feb 27 15:44:02 Machforr kern.warn kernel: [21925.480196] nf_conntrack: nf_conntrack: table full, dropping packet
Feb 27 15:44:02 Machforr kern.warn kernel: [21925.481983] nf_conntrack: nf_conntrack: table full, dropping packet
Feb 27 15:44:02 Machforr kern.warn kernel: [21925.484771] nf_conntrack: nf_conntrack: table full, dropping packet


There were a LOT more but the connection remained stable. I haven't tried during a system boot yet, but it looks similar than when I did the 'ping 1.1.1.1' command and I couldn't connect.
Let me know if it helps.
Sp1derman
DD-WRT User


Joined: 16 Jun 2006
Posts: 168
Location: Germany, BW

PostPosted: Tue Feb 27, 2024 21:26    Post subject: Reply with quote
whren you get this "Table full" message, pls go to Status/Router at buttom of page check "Maximum IP connections" and "Active IP connections"
Machforr
DD-WRT Novice


Joined: 17 Feb 2024
Posts: 22

PostPosted: Wed Feb 28, 2024 13:30    Post subject: Reply with quote
Well THAT was a mistake. Changing the IP from 192.168.1.1 to 192.168.5.1 completely killed the router... nothing accessible and the system is just borked. Currently on backup hardware.

No idea what happened... In the process of connecting screen and keyboard to the box to see what happens at boot. Will update.

UPDATE:
The boot sequence gets stuck there:
Code:
[httpd] : successfully startedudhcpc: sending discover 
udhcpc: sending discover


Hitting ctrl-C continues the boot process and I can log into the root. However my level of knowledge with linux is below level zero, the commands to initiate a reset are not known to me, if they would work at all.

UPDATE 2:
I managed to do a clean reinstall of my DD-WRT build. Got hairy for a moment, too.
Everything, except wifi and login credentials are at bone-stock default. Will test more after workday.
lexridge
DD-WRT Guru


Joined: 07 Jun 2006
Posts: 1244
Location: WV, USA

PostPosted: Wed Feb 28, 2024 21:03    Post subject: Reply with quote
Very freaking odd that only changing the Router IP from 192.168.1.1 to 192.168.5.1 borked it. This should NOT happen. If you had used ip a (see below) this would have told us a lot about what may have happened......

Here are some linux command line tools you should know how to use:

To show all your network interfaces and bridges.
ip a
or
ifconfig (outdated but still included)

ping IPADDR - which was already discussed previously

traceroute IPADDRorHOSTNAME - Traces the network path to the hostname/IP

cd - change directory

ls -l [PATH] - List the contents of the folder you are currently in or the optional PATH.

service - shows the available running and non-running services. Also used to start|stop|restart services

tail -f /var/log/messages - Monitor the log in realtime.

ps - shows all running processes

fsck [/dev/sdaN]- filesystem check for USB storage devices. Only use on non-mounted devices

cat - to print to screen any config or text files

free -h - Shows system memory both used and available

df -h - Shows disk usage

_________________
- Linksys EA8500: I-Gateway, AP/VAP 5ghz only r56820: Features: WDS-AP, VLANs, Samba, WG, Entware
- Linksys EA8500: WDS Station x2 - r56941
- Netgear R6400v2: WAP/VAP 2.4ghz only w/VLANs over single trunk port. r56820
- Netgear R7800 (WDS-AP, WAP/VAP) - r56820: Features in use: multiple VLANs over single trunk port
- Linksys MR7350: Testing r56941
- Linksys Velop WHW03v1 x2: OpenWRT w/GRETAP tunnel for VLANs on VAPs
- OSes: Fedora 38, 9 RPis (2,3,4,5), 20 ESP8266s: Straight from Amiga to Linux in '94, never having owned a Windows PC.

- Forum member #248
Machforr
DD-WRT Novice


Joined: 17 Feb 2024
Posts: 22

PostPosted: Wed Feb 28, 2024 21:44    Post subject: Reply with quote
Sorry I couldn't help you diagnose further. Having insight on what did happen would have helped with further builds, for sure.

But a bad installation or a corrupted setting was also something that was possible.
I'll say that despite the little post-install pains I got, things are tentatively looking good right now. Got full access and with mostly default settings, too.

I'll go slow and see what happens.

Thanks for the list of commands as well, saving those in a text doc for reference.
lexridge
DD-WRT Guru


Joined: 07 Jun 2006
Posts: 1244
Location: WV, USA

PostPosted: Thu Feb 29, 2024 4:56    Post subject: Reply with quote
Glad it is working finally. Be sure to do backups always before making changes, and again once you confirm the changes worked. You can find it under the Administration/Backup tab.
_________________
- Linksys EA8500: I-Gateway, AP/VAP 5ghz only r56820: Features: WDS-AP, VLANs, Samba, WG, Entware
- Linksys EA8500: WDS Station x2 - r56941
- Netgear R6400v2: WAP/VAP 2.4ghz only w/VLANs over single trunk port. r56820
- Netgear R7800 (WDS-AP, WAP/VAP) - r56820: Features in use: multiple VLANs over single trunk port
- Linksys MR7350: Testing r56941
- Linksys Velop WHW03v1 x2: OpenWRT w/GRETAP tunnel for VLANs on VAPs
- OSes: Fedora 38, 9 RPis (2,3,4,5), 20 ESP8266s: Straight from Amiga to Linux in '94, never having owned a Windows PC.

- Forum member #248
Machforr
DD-WRT Novice


Joined: 17 Feb 2024
Posts: 22

PostPosted: Thu Feb 29, 2024 15:06    Post subject: Reply with quote
It's "Working" in that I got things back to the status-quo: My issue still persists.
I noticed that the router gives this error when my VPN logs on:

Code:
Feb 29 15:50:31 DD-WRT daemon.warn dnsmasq[3070]: possible DNS-rebind attack on IPv6 detected: dns.msftncsi.com


Makes little sense as ipv6 is not even enabled.

Still, for a few minutes I thought my problem solved! The disconnect was not instantaneous.

I removed the AV program from both machines, too, as it HAD been interfering with my work VPN.

I'm of the mind that, right now, the modem's messing stuff up with the router. The ethernet switch is working as it should, since a simple reboot of the router reconnects every device. So the switch is doing its job.

I didn't have the logs enabled before the latest disconnection. I thought it necessary to at least do THAT test and see if logging interfered. I'll retest later and monitor closely.

Try WITH and Without VPN, see what happens.. that sort of stuff. Like I said, I'll go slow.

UPDATE:
Took a moment, but finally managed to find the dnsmasq options. Might seem obvious to some, but I'm new to the dd-WRT infrastructure.
Still, I added rebind-domain-ok=/dns.msftncsi.com/ to the dnsmasq options. It made the error go away and I'll see how much it stabilizes things.
Machforr
DD-WRT Novice


Joined: 17 Feb 2024
Posts: 22

PostPosted: Fri Mar 01, 2024 0:38    Post subject: Reply with quote
A new warning popped up. From what I could gather, it's in relation to a realtek driver?

Code:
kern.warn kernel: [15266.886426] r8169 0000:04:00.0 eth0: Rx ERROR. status = 352cc54e
Sp1derman
DD-WRT User


Joined: 16 Jun 2006
Posts: 168
Location: Germany, BW

PostPosted: Fri Mar 01, 2024 12:41    Post subject: Reply with quote
replace realtec NICs with Intel.
If you google Linux and r8168 or r8169 you will find a long history of problems. somtimes you have to update the NIC firmware or you have to replace drivers....
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