2 clients connecting from N2 over a single interface

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bk_XU_AZ
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2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

UPDATE: If you scroll to the bottom of this thread, you'll see that the issue I was having has nothing to do with Odroid, it was an ASUS router issue.

I use an Ethernet cable to plug my N2 into a router. That (Asus) router shows a network map with the N2 as a single device with a static IPV4 address. However, it has the number 2 superimposed on the client icon, and says "2 clients are connecting from this device" when I hover the mouse pointer over that. Every other device has a normal icon (and a single connection). Why does the N2 have two?

I'm running Hardkernel's Ubuntu Mate 20.04 (latest).

Image
Last edited by bk_XU_AZ on Thu Sep 10, 2020 1:19 pm, edited 1 time in total.

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Re: 2 clients connecting from N2 over a single interface

Post by tobetter »

Have you checked if two ODROID-N2 have different IP address? Have you changed the hostname of them?

"Tapatalk wishes you to have fun with ODROID"


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Re: 2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

Yes, good thought- I did check that first. There's the static IP address I assigned, and the loopback address, like every device. No other addresses though. Only one N2 is connected to this router. No other odroid machines, and nothing with the same MAC or IP address. The router says is from one device. Though I included two lines in my screen grab, the second is a tablet connected by WiFi.
Last edited by bk_XU_AZ on Tue Sep 08, 2020 3:42 pm, edited 1 time in total.

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Re: 2 clients connecting from N2 over a single interface

Post by lazlo »

IPv6 address?

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Re: 2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

lazlo wrote:
Tue Sep 08, 2020 3:38 pm
IPv6 address?
I wondered too if that's it. But no other machine (which all have IPV6 enabled show two connections) from this DHCP server.

I have an XU4 running on the same network running Ubuntu Mate 18.04. It has the very same symptom (different MAC, static IP and hostname of course). I disabled IPV6 (and checked it with "ip a") and the router still shows 2 connections from the XU-4 (and the N2). Baffling

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Re: 2 clients connecting from N2 over a single interface

Post by lazlo »

On the N2, check the output of ip addr. Look at the subsection for eth0. The line below is an IPv6 address:

Code: Select all

inet6 fe80::21e:6ff:fe42:5154/64 scope link
If you do not see a line like then you truly do not have an IPv6 address. You really should have one though because IPv6 is so important to so many system processes.

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Re: 2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

Yes, that command is the same as "ip a"- there's an ipv6 address until I disable it. But that's not the second client connecting from that device. I appreciate the help. I am stumped!

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Re: 2 clients connecting from N2 over a single interface

Post by lazlo »

Perhaps you are seeing an old connection (IP address lease) that hasn't expired yet. What happens if you reboot the router?

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Re: 2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

The list is actually updated about every 5 seconds. If I disable networking entirely, the connection goes away in the router's GUI. When I re-enable it, it reappears after a few seconds or so. I powered up the XU4 after I started this thread. Again- both devices use static IP addresses, so no lease involved (none evident on any of the three ends- two devices and a router- anyway).

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Re: 2 clients connecting from N2 over a single interface

Post by lazlo »

And your third device, it is running Ubuntu as well?

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Re: 2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

There are two Odroids running Ubuntu and a router. Both Odroids (N2 and XU4) have the same symptom (each shows 2 clients connected on the router).

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Re: 2 clients connecting from N2 over a single interface

Post by lazlo »

OK, I could be wrong but I think you are seeing one of three or four things:

A.) The connection from the IPv6 address on the N2+ before you disable it (and I don't know why you would because it breaks things when yo do that).

or

B.) The connection to router by the NIC before it gets renamed to eth0 by udev.

or

C.) The connection from Petitboot to the router before it gets handed off to the Ubuntu kernel.

or

D.) A VM or container running on the N2+ has a virtual NIC with seperate MAC and IP address.

The only reason you should see two active connections if because the device is connecting to the router with two different IP/MAC addresses.
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bk_XU_AZ (Wed Sep 09, 2020 6:31 pm)

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Re: 2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

I am going to look into C & D. I don't think I could have a VM container, since I haven't started one, nor installed a VM service. But... I never checked and don't know much about that. But I will do some research. I can tell you that the list displayed by the router is no older than a few seconds. It's not showing leases, but connected clients. I will be back with any discoveries. Thank you again.

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Re: 2 clients connecting from N2 over a single interface

Post by mad_ady »

In the router shell try running:

Code: Select all

arp -an | grep n2_mac
arp -an | grep n2_ip
See if it comes with two entries.

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Re: 2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

It's just one line for each command. I tried it on each machine. All 4 lines of the output look something like this (except different MAC and IP addresses on each machine):

Code: Select all

? (192.168.144.65) at 00:1e:06:29:e7:2b [ether]  on br0

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Re: 2 clients connecting from N2 over a single interface

Post by mad_ady »

Check out this thread, where lots of people complain of the same issue: https://www.snbforums.com/threads/2-cli ... ice.35934/
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bk_XU_AZ (Wed Sep 09, 2020 6:31 pm)

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Re: 2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

mad_ady wrote:
Wed Sep 09, 2020 1:28 pm
Check out this thread, where lots of people complain of the same issue: https://www.snbforums.com/threads/2-cli ... ice.35934/
THANK YOU! I Googled this a few times, and got garbage results mostly, and lots of dead ends before posting here. I never found the discussion you pointed out. Much appreciated. Hopefully I can figure this out. It's only with the Odroid ARM machines running Ubuntu, my wife's H2 behaves properly, and our other PCs and iMac (yuk) don't have this either.

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Re: 2 clients connecting from N2 over a single interface

Post by bk_XU_AZ »

Eureka! Turns out lazlo was on the right track and mad-ady pointed me to the thread that helped me find that out after exhausting my knowledge of how to troubleshoot it. The ASUS router has a "bug" where it remembers old MACs that it had assigned a DHCP address and counts that device, whether Odroid or anything else, as another connection. It will count the new static IP address, plus every single DHCP address it's ever given to that MAC. I didn't know there was an "old" DHCP list accessible on it. Once I deleted all of the old DHCP addresses, and rebooted the Odroids, the problem went away. Now it works as it should. I hope I don't forget about this. Thanks so much to both of you! Reminds me of the old adage "it takes a village to raise an idiot" (that's me).

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Re: 2 clients connecting from N2 over a single interface

Post by lazlo »

bk_XU_AZ wrote:
Wed Sep 09, 2020 2:53 pm
Eureka! Turns out lazlo was on the right track and mad-ady pointed me to the thread that helped me find that out after exhausting my knowledge of how to troubleshoot it. The ASUS router has a "bug" where it remembers old MACs that it had assigned a DHCP address and counts that device, whether Odroid or anything else, as another connection. It will count the new static IP address, plus every single DHCP address it's ever given to that MAC. I didn't know there was an "old" DHCP list accessible on it. Once I deleted all of the old DHCP addresses, and rebooted the Odroids, the problem went away. Now it works as it should. I hope I don't forget about this. Thanks so much to both of you! Reminds me of the old adage "it takes a village to raise an idiot" (that's me).

I'm glad it worked out for you. Don't feel bad because you ran into an unexpected bug in your network hardware. Instead feel good because you found the root cause of the issue.
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