Magical ethernet interface (network card not detected - electrical circuit issue?)

Written by - 0 comments

Published on - Listed in Hardware Personal Network Rant

This weekend I have seen  the strangest network problem ever. For two weeks now, a network card in a selfbuilt computer using an Intel motherboard (NIC on board) has been defect. Even the operating system (SLES11) didn't detect it anymore. Yesterday I had to take a look at it in person and unfortunately the network card seemed dead. Dead for the OS but not for the switch; the LED on port 3, where this computer was connected to, was still shiny green. Same thing on the network card on the motherboard: The LEDs were green.

I tested several things like new configuration of ifcfg-eth0, repair install, new netcard detection... but that all doesnt work if even "hwinfo --netcard" shows no info. So I tried it with a cdboot-Linux (Knoppix 6.2). But not even Knoppix could find a network card; which means the problem is hardware-related. Before giving up and getting ready to replace the motherboard I wanted to check if all internal connections are ok. So I unplugged all cables from the computer, including the power cable. I was just about to open the computer when I saw the impossible: The LED for port 3 on the network switch was still a steady green!

Now THAT is very odd. No power, no network connection but the lights are on... Now I unplugged the network cable from the switch, releasing the "electrical circuit" from port 3. As expected the LED turned off. I plugged all the cables again to the computer and gave it another try - boot that thing. I also replugged the network cable to the switch. At the time of boot the switch LED turned on, starting to blink once in a while. Then I turned my head to the monitor where SLES11 was booting. And to my surprise the network card was detected, the configuration with static IP set and everything was up.

I have never seen a network problem like that, somehow completely deactivating the network card to work or even to be detected anymore, but hey, that's a first. Some electrical signal/discharge or whatever was between the switch and this computer causing the switch to freeze the port and the computers network card to be completely out - until I cut the remaining electrical circuit by pulling the network cable from the switch.

Add a comment

Show form to leave a comment

Comments (newest first)

No comments yet.

RSS feed

Blog Tags:

  AWS   Android   Ansible   Apache   Apple   Atlassian   BSD   Backup   Bash   Bluecoat   CMS   Chef   Cloud   Coding   Consul   Containers   CouchDB   DB   DNS   Database   Databases   Docker   ELK   Elasticsearch   Filebeat   FreeBSD   Galera   Git   GlusterFS   Grafana   Graphics   HAProxy   HTML   Hacks   Hardware   Icinga   Influx   Internet   Java   KVM   Kibana   Kodi   Kubernetes   LVM   LXC   Linux   Logstash   Mac   Macintosh   Mail   MariaDB   Minio   MongoDB   Monitoring   Multimedia   MySQL   NFS   Nagios   Network   Nginx   OSSEC   OTRS   Office   PGSQL   PHP   Perl   Personal   PostgreSQL   Postgres   PowerDNS   Proxmox   Proxy   Python   Rancher   Rant   Redis   Roundcube   SSL   Samba   Seafile   Security   Shell   SmartOS   Solaris   Surveillance   Systemd   TLS   Tomcat   Ubuntu   Unix   VMWare   VMware   Varnish   Virtualization   Windows   Wireless   Wordpress   Wyse   ZFS   Zoneminder