[ale] Odd network issue

Lightner, Jeff JLightner at dsservices.com
Thu Jul 9 09:17:22 EDT 2015

We have a server that appears to be unable to connect to various IPs (mostly printers) in our WAN at times.

The odd thing is that the interface is not down on either the server or the printer.   The server can reach multiple other IPs when this occurs but for some reason can't reach a few.    Similarly when this occurs we can reach these other IPs from other servers in the same VLAN.

There are no errors shown in statistics on the interface (eth0) on the server nor on the port it attached to on the switch.   There are no errors shown in /var/log/messages or dmesg.

The IPs are not always the same ones.   In fact yesterday when we saw the issue on IPs I tested the IPs that it couldn't reach the day before that I'd resolved and they were still working.

We've tried:
Killing the lp process that is hung at the start of this issue on server side.
Clearing arp on the server.
Clearing arp on the switch.
Bouncing cups (note issue is NOT just cups - when this occurs we can not ping the affected IPs nor can we telnet in on port 9100 as we would normally be able to do).

The only thing that seems to resolve the issue (and does each time) is having the interface bounce on the server.
We''ve done that by:
Rebooting the server
Ifup/ifdown on the server interface
Removing and reseating the cable.
Resetting the switch port.
In each of those we see the port go down then come back up and after that the previously unreachable IPs are again reachable.

I'm suspecting a bad interface port on either the server or the switch but in the absence of actual errors can't prove one way or the other.

This is different than any other network issue I've seen.   I'm wondering if anyone has run into this and can shed any light on it?

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