Red Hat Bugzilla – Bug 234075
Using PERSISTENT_DHCLIENT with no link present
Last modified: 2014-03-16 23:06:07 EDT
Description of problem:
The machines we have come up significantly faster than the switch which they are
connected to. Because of this, the network device never gets started. Setting
PERSISTENT_DHCLIENT=yes solves part of the problem. The part that is causing a
problem, however, is that ifup-ethX uses the check_link_down() function to
determine if a link is present. If there is not link present, it exits and
never bothers to start dhclient for the device. In this case, there is no link
present yet as the switch is still booting. It would be nice if there were
another option that could be added to ifcfg-ethX which would allow us to shut
off the check_link_down() check. It would be nice to have in conjunction with
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Configure eth device to use dhcp
2. Boot machine or restart the network without the network cable plugged in.
The network interface and dhclient will not start.
Created a quick, simple patch which essentially checks CHECK_LINK_DOWN to
determine whether or not to execute the check_link_down function.
Setting PERSISTENT_DHCLIENT=yes and CHECK_LINK_DOWN=no in a ifcfg-ethX and
dhclient will always start.
Created attachment 150965 [details]
ifup-eth CHECK_LINK_DOWN patch
Why not just use LINKDELAY or NETWORKDELAY for your switch?
(In reply to comment #2)
> Why not just use LINKDELAY or NETWORKDELAY for your switch?
We want devices to still come up normally if the switch is already up and the
link is present. Wouldn't using those *always* create a delay at startup?
Hm. I'd wonder if in the case of PERSISTENT_DHCLIENT, the link status should be
ignored *by default* - I'm not sure in what case you'd actually want to ever exit.
(In reply to comment #4)
> Hm. I'd wonder if in the case of PERSISTENT_DHCLIENT, the link status should be
> ignored *by default* - I'm not sure in what case you'd actually want to ever exit.
Didn't think about that prior.. But now that you mention it, yea, that seems to
make the most sense.
Added in CVS, will be in 8.52-1.