Bdtyktl

I use NetworkManager (Arch Linux) on my laptop in order to connect to wireless networks. I use the official GNOME GUI. Everything works fine, but after half an hour or so the network is still connected, but the default gateway just disappears from the routing table.

➜  log  ip r                                 

10.135.1.0/24 dev wlan0  proto kernel  scope link  src 10.135.1.3  metric 303 

10.135.1.3 via 127.0.0.1 dev lo  metric 303

The default gateway should be 10.135.1.138 and I can actually ping it. I can restore it if I reconnect, restart NetworkManager or use "ip r" to add it back manually, but it will be gone again after a half an hour.

I tried two different WiFi drivers and it happens with both. I tried using wicd instead of NetworkManager and it seemed to solve the problem. However, I'm not happy with wicd for several other reasons and I'm curious to know what's wrong with NetworkManager. I checked that netctl and wicd are disabled while NetworkManager is running (are there any other services which might interfere with it?).

This is the log from the last hour. I couldn't find anything suspicious in it, though:

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> (wlan0): device state change: prepare -> config (reason 'none') [40 50 0]

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> Activation (wlan0/wireless): connection 'KrustyKrab' has security, and secrets exist.  No new secrets needed.

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> Config: added 'ssid' value 'KrustyKrab'

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> Config: added 'scan_ssid' value '1'

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> Config: added 'key_mgmt' value 'WPA-PSK'

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> Config: added 'auth_alg' value 'OPEN'

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> Config: added 'psk' value '<omitted>'

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 2 of 5 (Device Configure) complete.

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> Config: set interface ap_scan to 1

Jan 18 17:36:39 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: inactive -> scanning

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: scanning -> authenticating

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: authenticating -> associating

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: associating -> 4-way handshake

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: 4-way handshake -> completed

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> Activation (wlan0/wireless) Stage 2 of 5 (Device Configure) successful.  Connected to wireless network 'KrustyKrab'.

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 3 of 5 (IP Configure Start) scheduled.

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 3 of 5 (IP Configure Start) started...

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> (wlan0): device state change: config -> ip-config (reason 'none') [50 70 0]

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Beginning DHCPv4 transaction (timeout in 45 seconds)

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> dhcpcd started with pid 2403

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Beginning IP6 addrconf.

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 3 of 5 (IP Configure Start) complete.

Jan 18 17:36:40 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed nbi -> preinit

Jan 18 17:36:50 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed preinit -> bound

Jan 18 17:36:50 tarsonis NetworkManager[2382]: <info>   address 10.135.1.3

Jan 18 17:36:50 tarsonis NetworkManager[2382]: <info>   prefix 24 (255.255.255.0)

Jan 18 17:36:50 tarsonis NetworkManager[2382]: <info>   gateway 10.135.1.138

Jan 18 17:36:50 tarsonis NetworkManager[2382]: <info>   nameserver '10.135.1.138'

Jan 18 17:36:50 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 5 of 5 (IPv4 Configure Commit) scheduled...

Jan 18 17:36:50 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 5 of 5 (IPv4 Commit) started...

Jan 18 17:36:51 tarsonis NetworkManager[2382]: <info> (wlan0): device state change: ip-config -> secondaries (reason 'none') [70 90 0]

Jan 18 17:36:51 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 5 of 5 (IPv4 Commit) complete.

Jan 18 17:36:51 tarsonis NetworkManager[2382]: <info> (wlan0): device state change: secondaries -> activated (reason 'none') [90 100 0]

Jan 18 17:36:51 tarsonis NetworkManager[2382]: <info> NetworkManager state is now CONNECTED_GLOBAL

Jan 18 17:36:51 tarsonis NetworkManager[2382]: <info> Policy set 'KrustyKrab' (wlan0) as default for IPv4 routing and DNS.

Jan 18 17:36:51 tarsonis NetworkManager[2382]: <info> Writing DNS information to /usr/bin/resolvconf

Jan 18 17:36:51 tarsonis NetworkManager[2382]: <info> Activation (wlan0) successful, device activated.

Jan 18 17:36:51 tarsonis NetworkManager[2382]: <warn> Dispatcher failed: (32) Unit dbus-org.freedesktop.nm-dispatcher.service failed to load: No such file or directory.

Jan 18 17:37:01 tarsonis NetworkManager[2382]: <info> (wlan0): IP6 addrconf timed out or failed.

Jan 18 17:37:01 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 4 of 5 (IPv6 Configure Timeout) scheduled...

Jan 18 17:37:01 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 4 of 5 (IPv6 Configure Timeout) started...

Jan 18 17:37:01 tarsonis NetworkManager[2382]: <info> Activation (wlan0) Stage 4 of 5 (IPv6 Configure Timeout) complete.

Jan 18 18:06:50 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed bound -> (null)

Jan 18 18:06:55 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed (null) -> bound

Jan 18 18:06:55 tarsonis NetworkManager[2382]: <info>   address 10.135.1.3

Jan 18 18:06:55 tarsonis NetworkManager[2382]: <info>   prefix 24 (255.255.255.0)

Jan 18 18:06:55 tarsonis NetworkManager[2382]: <info>   gateway 10.135.1.138

Jan 18 18:06:55 tarsonis NetworkManager[2382]: <info>   nameserver '10.135.1.138'

Jan 18 18:36:56 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed bound -> (null)

Jan 18 18:37:01 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed (null) -> bound

Jan 18 18:37:01 tarsonis NetworkManager[2382]: <info>   address 10.135.1.3

Jan 18 18:37:01 tarsonis NetworkManager[2382]: <info>   prefix 24 (255.255.255.0)

Jan 18 18:37:01 tarsonis NetworkManager[2382]: <info>   gateway 10.135.1.138

Jan 18 18:37:01 tarsonis NetworkManager[2382]: <info>   nameserver '10.135.1.138'

Jan 18 18:48:23 tarsonis NetworkManager[2382]: <warn> Connection disconnected (reason -4)

Jan 18 18:48:23 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: completed -> disconnected

Jan 18 18:48:23 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: disconnected -> scanning

Jan 18 18:48:24 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: scanning -> authenticating

Jan 18 18:48:24 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: authenticating -> associating

Jan 18 18:48:24 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: associating -> 4-way handshake

Jan 18 18:48:24 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: 4-way handshake -> completed

Jan 18 19:07:01 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed bound -> (null)

Jan 18 19:07:07 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed (null) -> bound

Jan 18 19:07:07 tarsonis NetworkManager[2382]: <info>   address 10.135.1.3

Jan 18 19:07:07 tarsonis NetworkManager[2382]: <info>   prefix 24 (255.255.255.0)

Jan 18 19:07:07 tarsonis NetworkManager[2382]: <info>   gateway 10.135.1.138

Jan 18 19:07:07 tarsonis NetworkManager[2382]: <info>   nameserver '10.135.1.138'

Jan 18 19:13:27 tarsonis NetworkManager[2382]: <warn> Connection disconnected (reason -4)

Jan 18 19:13:27 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: completed -> disconnected

Jan 18 19:13:27 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: disconnected -> scanning

Jan 18 19:13:28 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: scanning -> authenticating

Jan 18 19:13:28 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: authenticating -> associating

Jan 18 19:13:28 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: associating -> 4-way handshake

Jan 18 19:13:28 tarsonis NetworkManager[2382]: <info> (wlan0): supplicant interface state: 4-way handshake -> completed

Jan 18 19:37:07 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed bound -> (null)

Jan 18 19:37:13 tarsonis NetworkManager[2382]: <info> (wlan0): DHCPv4 state changed (null) -> bound

Jan 18 19:37:13 tarsonis NetworkManager[2382]: <info>   address 10.135.1.3

Jan 18 19:37:13 tarsonis NetworkManager[2382]: <info>   prefix 24 (255.255.255.0)

Jan 18 19:37:13 tarsonis NetworkManager[2382]: <info>   gateway 10.135.1.138

Jan 18 19:37:13 tarsonis NetworkManager[2382]: <info>   nameserver '10.135.1.138'

What's really odd is that it actually shows "gateway 10.135.1.138" although it won't appear in the routing table unless I reconnect.

You don't happen to have netctl activated, do you?

   sudo systemctl status netctl

The Wiki explicitly states:

There are many solutions to choose from, but remember that all of them are mutually exclusive; you should not run two daemons simultaneously.

The solution it refers to are Connman, Netctl, NetworkManager, Wicd. For instance, I too use only NetworkManager.

I'm having exactly the same problem and my environment is very similar to yours.
I'm also on Arch linux, using Network manager with a wireless network card.

Have you tried using dhclient instead of dhcpcd?
https://wiki.archlinux.org/index.php/NetworkManager#dhcpcd_repetitively_refusing_leases

Edit:
To be more explicit and to include linked material in the post:
The problem of the lost default gateway could be caused by dhcpcd refusing leases.
So what solved the problem for me as per the above link is to make network manager use dhclient.
To do that, add
dhcp=dhclient
under the main section in /etc/NetworkManager/NetworkManager.conf and then restart the NetworkManager service.

Also make sure that the dhclient package is installed first.
HTH