Disappearing routes in HN - Revision history

Kir: Networking: disappering routes in HN moved to Disappearing routes in HN: Fixed to typo + no need to put category in page name.

2007-12-03T15:39:23Z

Networking: disappering routes in HN moved to Disappearing routes in HN: Fixed to typo + no need to put category in page name.

Dev at 14:40, 3 December 2007

2007-12-03T14:40:31Z

Dev: New page: == Problem statement == Sometimes people complain about VE-related routes disappering in HN. These routes usually look like this: # ip r l 192.168.225.195 dev venet0 scope li...

2007-12-03T14:39:47Z

New page: == Problem statement == Sometimes people complain about VE-related routes disappering in HN. These routes usually look like this: # ip r l <skip> 192.168.225.195 dev venet0 scope li...

New page

== Problem statement ==

Sometimes people complain about VE-related routes disappering in HN.

These routes usually look like this:

# ip r l
<skip>
192.168.225.195 dev venet0 scope link

and tell the kernel that IP address 192.168.225.195 belongs to venet0 device. Thus
packets with destination IP equal to 192.168.225.195 are forwarded to venet0 and
then to appropriate VE.

== Resolution ==

The problem is usually one of these:
# '''DHCP client'''. If your '''''host system''''' uses DHCP for acquiring IP address, then DHCP is for sure to blame. DHCP client tries to be smart and resets all the routes to those got from the server. Check your logs for DHCP re-lease events or other messages correlating with routes disappearing.
# '''Hotplug events'''. Modern Linux distros come with hotplug subsytem which tries to handle events like "new device found", "device was unplugged", etc. It also tries to be smart when LINK is DOWN/UP event from network device is received and can remove manually set routes. Check that your dmesg have anything related to this events. (AFAIK SUSE is the worst distro in this regard).

== Debugging ==

If you still can find what happens with your network settings try to replace /sbin/ip and /sbin/route with scripts
logging the commands and programs which executed them and calling original binaries after that.
This will help to find the victim if it's some script. More robust but similar debug can be added
to kernel if first approach doesn't help.

[[Category: Troubleshooting]]
[[Category: Networking]]

← Older revision	Revision as of 15:39, 3 December 2007
(No difference)

@@ Line 21: / Line 21: @@
 == Debugging ==
-If you still can find what happens with your network settings try to replace /sbin/ip and /sbin/route with scripts
+If you still can't find what happens with your network settings try to replace /sbin/ip and /sbin/route with scripts
 logging the commands and programs which executed them and calling original binaries after that.
 This will help to find the victim if it's some script. More robust but similar debug can be added