Change duplex setting on vSphere Service Console

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During a training a student accidentally changed the duplex setting of the vmnic for the service console to fixed 1000Mbit full duplex. This isn’t so bad, if the vmnic wasn’t on a 100Mbit switch!

So I had to go to the service console to change the duplex setting back to auto.
I expected to use the esxcfg-vswif command. But with this command you cannot change the duplex setting. After some investigation I discovered to use normal Linux command like ethtool.

To see the current settings:

ethtool vmnic1

To change the settings to 1000Mbit full duplex:

ethtool -s vmnic1 autoneg off
ethtool -s vmnic 1 speed 1000 duplex full

To change it backup again to auto:

ethtool -s vmnic1 autoneg on

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Twitter

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It took a while but inspirited by a girlfriend Maggie van Kempen I registered for a Twitter account. I plan to use my Twitter not to let you all know if I go to the toilet or something like that, but just to announce new interesting blog articles written by me. So if you like to get notified through Twitter, please click the follow me link!

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Configuring a SLES DHCP failover

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In most networks DHCP is one of the single-point-of-failures. If DHCP failes, every devices relying on DHCP cannot function.

In order to  provide a high availability to your DHCP server, set up a backup DHCP server running the same Linux distribution and version, as follows:

1. Stop DHCP on both DHCP servers (rcdhcpd stop).
2. On your primary DHCP server, add lines to the /etc/dhcpd.conf file, similar to following example:

   failover peer "dhcp" {
      primary;
      address 192.168.1.10;          # local host IP address
      port 647;                      # make sure this port is not used by other
                                       programs
      peer address 192.168.1.11;     # backup host IP address
      peer port 647;
      max-response-delay 60;
      max-unacked-updates 10;
      mclt 600;
      split 128;
      load balance max seconds 3;
   }
   include "/etc/dhcpd.master";

   On your backup DHCP server, add lines to the /etc/dhcpd.conf file, similar to following example:

   failover peer "dhcp" {
      secondary;
      address 192.168.1.11;         # local host IP address
      port 647;                     # make sure this port is not used by other
                                      programs
      peer address 192.168.1.10;    # primary host IP address
      peer port 647;
      max-response-delay 60;
      max-unacked-updates 10;
   }
   include "/etc/dhcpd.master";

3. Add the following lines to the end of /etc/dhcpd.master on both DHCP servers. On SUSE Linux Enterprise Server, copy this file to /var/lib/dhcp/etc.

   subnet 192.168.1.0 netmask 255.255.255.0 {
     pool {
       failover peer "dhcp";
       range 192.168.1.100 192.168.1.200;
       deny dynamic bootp clients;
     }
     option routers 192.168.1.1;
   }

4. Start DHCP on both DHCP servers (rcdhcpd start.

After these configurations are complete, the primary DHCP server, which is usually a management server or install server, responds to DHCP client requests. If the primary DHCP server goes offline, the backup DHCP server automatically takes its place and provides DHCP service.

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