OUCS Backbone Network Naming and Numbering Conventions

Posted on 2011-08-15 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

Firewall firefighting

Posted on 2011-07-01 by Andy Saunders

The intention of this post is to explain what’s been happening with the University Firewall, what we’ve been doing about it and what we intend to do. The University Firewall Service is provided by a pair of Cisco FWSMs running … Continue reading →

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Budget High Availability ASA testing

Posted on 2011-05-24 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 | Comments Off on Budget High Availability ASA testing

Joe Job Spam Run

Posted on 2011-05-03 by Guy Edwards

The university received two spam run campaigns, the first uses a forged sender to make a university address look like the sender, the second uses forged university addresses (i.e. not accounts) in an outgoing campaign to other sites, resulting in … Continue reading →

Posted in Mail Relay | 2 Comments

DNS troubleshooting

Posted on 2011-03-02 by Guy Edwards

I thought I’d write a quick reference for support staff not familiar with DNS troubleshooting The basics: DNS requests query a server to ask, for instance, what the IP address of a website is, when all you know is the … Continue reading →

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MAC Flaps – why are they bad?

Posted on 2011-02-04 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 | 6 Comments

IPv6 Stateful Active/Standby Failover with Cisco ASAs

Posted on 2011-01-28 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

DNSSEC first steps

Posted on 2011-01-14 by Andy Saunders

DNSSEC is a security extension to the Domain Name System which offers origin authentication of DNS data data integrity authenticated denial of existence This is useful in helping to protect against attacks such as DNS cache poisoning. Information on DNSSEC … Continue reading →

Posted in DNS | 3 Comments

BBC iPlayer and the University VPN

Posted on 2011-01-04 by Guy Edwards

[edit] Since writing this an iPlayer developer has passed on via informal channels that they’re using the Quova geolocation service. In this database part of our VPN address range was designated an ‘international proxy’ – while this may be regarded … Continue reading →

Posted in General Maintenance, VPN, Wireless | Comments Off on BBC iPlayer and the University VPN

AOL mail

Posted on 2010-12-21 by Guy Edwards

Just a minor post about an issue some people might have seen (things are fairly quiet in the runup to Christmas). If you had an issue delivering mail to or from an aol.com address today this post explains why. I … Continue reading →

Posted in Mail Relay | Comments Off on AOL mail