October 18, 2017 by James

Re-install telnet, ftp etc on OSX High Sierra

Updated your mac then realised that telnet is missing (when you’re cross legged on a datacentre floor, probably) ? Read on…

June 27, 2017 by James

VMWare consolidation issue – Could not open/create change tracking file.

Troubleshooting a VM that was failing snapshot consolidation with the error:

b372d49a-dfc9-b8ac6f98410c/GUESTVM/GUESTVM_1-ctk.vmdk: Could not open/create change tracking file. 2017-05-23T07:51:36.671Z| vcpu-0| I120: DISKLIB-VMFS : “/vmfs/volumes/4ea7e864-b372d49a-dfc9-b8ac6f98410c/GUESTVM/GUESTVM_1-flat.vmdk” : closed.

February 10, 2016 by James

Troubleshooting High CPU usage on a Catalyst 6500 due to ARP Input.

Faced with a Cat 6500 with dual Sup 2T's that responded to a show running-config with Unable to read Configuration.Try Again later and general cli slowness, it became aparrent that the CPU load on the supervisors was massive: cat-6500-sw1#sh proc cpu sorted CPU utilization for five seconds: 99%/83%; one minute: 99%; five minutes: 99% PID…

August 2, 2013 by James

Monitoring and graphing signal strength on a Wavecom serial GSM modem using perl and cacti.

Todays problem: Frequent errors and dropouts on a Wavecom 900E GSM modem we use to send SMS alerts to our engineering team. Following on from a spell of frustrating problems with one of our alerting systems I decided to see if I could graph the received signal strength on our GSM modem to determine if that…

July 3, 2013 by James

Migrating from IOS to IOS-XE – interface rate-limit

Historically I've used simple access-lists and interface rate-limit commands to act as a backstop preventing the network being overwhelmed by runaway traffic flows (UDP from DNS reflection attacks being the flavour of the month). On standard IOS boxes (7206-NPEG2 in this case) it was quite simple to follow the recommendations in the secure IOS template…

May 16, 2013 by James

Raspberry PI as a wireless bridge..

I'm using a RPi with an Edimax usb wireless controller to bridge the home wireless network into a switch with some kit connected that I would rather not cable up to. Once you've got the wireless set up (using the wpa_gui or any number of cli variants the rest is nice and easy – if…

April 5, 2013 by James

A blast from the past is always amusing…

I do enjoy it when I find something I've written that makes me think 'cool!' when I read it again: This virtual name server node requires some out of the ordinary config to work, due to the way VMWare's switches behave. You'll need to set promiscous mode -> yes in the vDS portgroup config, ensure the…

March 5, 2013 by James

(amusingly|scarily) accurate !

March 4, 2013 by James

Get the last column from the output of ls -l

so, with a file/output like this: drwxrwxr-x 35 user1 www 1536 May 13 2010 dir1 drwxrwxr-x 19 user2 www 512 Sep 28 11:36 dir2 drwxrwxr-x 5 user3 www 1024 Jan 11 2010 dir3 drwxrwxr-x 5 user4 www 398848 Oct 5 2010 dir4 drwxrwxr-x 10…