Odd network behavior

[Ken D'Ambrosio]

Based on your description, it sounds an *awful* lot like one of your 
routers -- the one you're plugged into -- is power cycling occasionally. 
  I'd watch the LEDs on the router (especially when you lose 
connectivity) and see if they seem to be indicating a boot sequence.  If 
so, I'd check that the power supply and cables are well-plugged-in; if 
they are, I might consider a new router.  But first, I'd try a different 
wall power place, just for kicks.

-Ken

On 2017-08-01 00:07, rikona wrote:
> I'm seeing some odd network behavior that I don't understand. The
> problem started when I decided to improve the wireless coverage in my
> house by using an extra router as second access point. Both routers
> have the same SSID and the same encryption and password. The second
> router has different LAN IP address, a different channel[using 5 and
> 9], and the DHCP server is turned off in the second router/access
> point. This second router/access point does work and does extend the
> wireless coverage significantly, so that function seems to be working.
> 
> But, I started noticing on my Ubuntu box that I was periodically losing
> my network connection about every 5 to 20 minutes. The connection would
> go down for a couple of minutes then come back up. When the connection
> went down, all the lights next to each CAT5 connector would go off
> completely [which seemed odd], not even flickering. After a minute or
> two the input CAT5 connector light would go on, followed shortly by the
> rest of the CAT5 connector lights, and the network would be up.
> 
> At first I was blaming Comcast because their local service is not at
> all reliable, but after a day or so I began to consider that the
> problem might be at my end. I have another router [primarily used by
> someone else as a DMZ] ahead of both of the above routers, and that DMZ
> connection did not seem to be going down which showed that the problem
> was at my end and not at Comcast.
> 
> I thought I might get some clues by looking at syslog, which does show
> these disconnects. The log is very large, but I'm hoping the following
> excerpts might provide enough clues to understand what is going on.
> 
> This snippet shows the disconnect:
> 
> "
> NetworkManager[918]: <info>  [1501536278.6169] device (enp4s0): link
> disconnected
> NetworkManager[918]: <info>  [1501536278.6170] device (enp4s0): state
> change: activated -> unavailable (reason 'carrier-changed') [100 20 40]
> .....
> NetworkManager[918]: <info>  [1501536278.6281] manager: NetworkManager
> state is now DISCONNECTED
> "
> and the following snippet shows the reconnect:
> 
> "
> NetworkManager[918]: <info>  [1501536319.8205] device (enp4s0): link
> connected kernel: [2495080.876510] igb 0000:04:00.0 enp4s0: igb: enp4s0
> NIC Link is Up 1000 Mbps Full Duplex
> NetworkManager[918]: <info>  [1501536319.8228] manager: NetworkManager
> state is now CONNECTING
> ...
> NetworkManager[918]: <info>  [1501536319.8452] policy: set 'Wired
> connection 1' (enp4s0) as default for IPv4 routing and DNS
> ...
> nmbd[1466]: [2017/07/31 14:27:07.998589,  0]
> /source3/nmbd/nmbd_become_lmb.c:397(become_local_master_stage2)
> nmbd[1466]:   Samba name server CHEWIE is now a local master browser
> for workgroup FAMILY
> "
> NOTE - this computer IS the one that I would like to be the master
> browser for the workgroup, so that part is working as I'd like.
> 
> The network then functions okay for 5 to 20 minutes, then repeats the
> same disconnect/reconnect again and again.
> 
> At this point I disconnected the second router/access point and the
> behavior changed. It no longer disconnects/reconnects, but the network
> behavior in the Ubuntu box is different, and not what I want.
> 
> At the next reconnect we get:
> 
> NetworkManager[918]: <info>  [1501536890.1845] manager: NetworkManager
> state is now CONNECTING
> ...
> 
> nmbd[1466]: [2017/07/31 14:39:06.910864,  0]
> ../source3/nmbd/nmbd_incomingdgrams.c:304(process_local_master_announce)
> nmbd[1466]: [a different Linux computer ] is announcing itself as a
> local master browser for workgroup FAMILY and we think we are master.
> Forcing election.
> nmbd[1466]:   Samba name server CHEWIE has stopped being a local master
> browser for workgroup FAMILY
> 
> [1] Now this is NOT what I want, but it is not clear to me why this box
> has stopped being a local master browser for the workgroup. I would
> appreciate any insights as to why that happened, and how I can get the
> original 16.04 computer to be the master browser, and stay that way.
> 
> [2] Also, it is not clear to me why adding the second router as an
> access point caused the first router to periodically stop working. I
> would also appreciate VERY MUCH any insights as to why that might
> happen.
> 
> I can post the entire logs if that would be helpful, but they are quite
> large - please let me know if I should do that.
> 
> Thanks for reading this...