VPN NAT Changes

Posted on 9 January 2012 by Guy Morrell

What is this post about? We are planning to make a minor change to the way our VPNs NAT clients. For those who are interested, this blog post explains why and how we are doing this. Please note that these … Continue reading →

Posted in Cisco Networks, Documentation, General Maintenance, VPN | Leave a comment

OUCS Backbone Network Naming and Numbering Conventions

Posted on 15 August 2011 by Guy Morrell

Introduction This blog post is intended to help ITSS in Oxford to better understand how the centrally provided network fits together with their own local networks. It is also hoped it will assist them in assessing the impact of any … Continue reading →

Posted in Backbone Network, Cisco Networks, Documentation, General Maintenance | 1 Comment

Budget High Availability ASA testing

Posted on 24 May 2011 by Guy Morrell

The problem We’re looking at setting up a management network behind a couple of ASAs. My requirements and prerequisites are: No L2 end to end VLANs through the core. That is bad and wrong. A total site failure at one … Continue reading →

Posted in Cisco Networks, Firewall | Leave a comment

MAC Flaps – why are they bad?

Posted on 4 February 2011 by Guy Morrell

What is a MAC Flap? A MAC Flap is caused when a switch receives packets from two different interfaces with the same source MAC address. If this makes no sense, perhaps a  quick summary of how switching at layer 2 … Continue reading →

Posted in Backbone Network, Best Practices, Cisco Networks | Tagged | 2 Comments

IPv6 Stateful Active/Standby Failover with Cisco ASAs

Posted on 28 January 2011 by Guy Edwards

There was some debate on the Cisco ASA failover situation with regard to IPv6. Since we’re potentially about to make a interim firewall purchase for the main university IPv6 traffic (we route IPv6 separately to IPv4 to avoid a limitation … Continue reading →

Posted in Cisco Networks, Firewall, IPv6 | 1 Comment

Changes in the core

Posted on 8 March 2010 by Guy Morrell

On Tuesday 2nd March we made two significant changes in the Core. Both are inline with current Cisco best practice are have been implemented as part of our Backbone ‘feature update’ project. VTP We have moved to using VLAN Trunking … Continue reading →

Posted in Backbone Network, Best Practices, Cisco Networks, Services | Leave a comment

Wireless – what could possibly go wrong?!

Posted on 1 February 2010 by Oliver Gorwits

I love this slide from a Troubleshooting Wireless Networks talk I attended last week. It says a lot about how difficult it is to tackle trouble tickets of the “client can’t connect to network” variety.

Posted in Cisco Networks, Wireless | Leave a comment

Cisco firewall SMTP “fixup” considered harmful

Posted on 26 November 2009 by Oliver Gorwits

This issue is old and familiar to us, and crops up about once every six months or so. I thought it might help to document the situation more publicly. On Cisco firewalls (PIX or the newer ASA), various protocol inspection … Continue reading →

Posted in Cisco Networks, Firewall, Mail Relay, Message Submission | 1 Comment

Connecting to JANET

Posted on 6 October 2009 by Oliver Gorwits

Sorry it’s been a little while since our last post. We’re just coming to the end of the summer vacation, the point when we (and most other IT support staff around the university) get things ship-shape in time for the … Continue reading →

Posted in Backbone Network, Cisco Networks | Leave a comment