Thursday, November 5, 2015

Changing the case of a Windows hostname

Naming convention is something that I’m very particular about and one thing that has always bugged me is if hostnames are not the same case.  In the Windows world there is no functional difference between upper and lowercase hostname, but it’s still enough to bother me.

To change the case is surprisingly easy.

First we log onto “Active Directory Users and Computers” and enable the “Advanced Features” which lives in the View menu.


Double-click the offending hostname and go to the “Attribute Editor”.  Scroll down to the dNSHostName and change the case.


The change will take effect as soon as you reboot the host in question.

Wednesday, November 4, 2015

Cisco traceroute status codes

Just a quickie.  Cisco routers can give seemingly weird (especially if you’re coming from the Windows world) traceroute outputs.  This is something that I did not see documented in either the CCNA or CCNP training guides.

In Cisco routers, the codes for a traceroute command reply are:
! -- success
* -- time out
N -- network unreachable
H -- host unreachable
P -- protocol unreachable
A -- admin denied
Q -- source quench received (congestion)
? -- unknown (any other ICMP message)

For further reading refer to the IBM AIX documentation – as far as I can make out the AIX codes applies to Linux as well.

Friday, October 30, 2015

Setting up a Cisco port-channel

Setting up port-channels on a Cisco switch can sometimes be a real PITA due to your interface settings having to match the port-channel settings.  I’ve come up with a way to eliminate the config mismatches, which I’ll describe below.

First we clear the configuration on the interfaces that we’re going to add to our port-channel by doing a “default int gi1/1/1

Then we add our interfaces to the port-channel and only then do we configure our port-channel, like so:

int gi1/1/1
channel-group <x> mode active
int gi2/1/1
channel-group <x> mode active
int po<x>
switchport mode trunk
switchport trunk allowed vlan 10,50,...
switchport trunk native vlan 999

This forces your interfaces to join the port-channel before any configuration is added to them. It also reduces the mistake of having mismatched configuration on both interfaces, which could cause independent members in your port-channel.

Thursday, October 29, 2015

FortiAP does not broadcast on 5Ghz Radio–shows channel 0

I recently had a problem where a customer’s FortiAP 221C AP’s would intermittently stop broadcasting the SSID’s assigned to the 5Ghz Radio.

I had a look at the FortiAP profiles and saw that all channels were selected, including channels 149, 153, 157, 161 and 165.  I deselected those so that my configuration was as per below:


Once I did that the AP’s started broadcasting on 5Ghz again.  Not sure yet if this is a regulatory limitation due to my country code (ZA) or a bug.