Kerry Thompson
Author's posts
Explained: The Different Types of Network Address Translation (NAT)
In this post I explain the different types of NAT and why you need to use them. With the shortages of IPv4 addresses and the yet-to-arrive nirvana of IPv6 we’re still using NAT to maintain network connectivity, and network engineers everywhere need to know how and when to use NAT.
Permanent link to this article: https://crypt.gen.nz/2025/08/28/explained-the-different-types-of-network-address-translation-nat/
When is the best time of year to get a Security job in Auckland?
Over the last couple of years I have gathered the number of new job postings for particular jobs advertised on Seek. Here’s the results.
Permanent link to this article: https://crypt.gen.nz/2018/11/19/when-is-the-best-time-of-year-to-get-a-security-job-in-auckland/
Timing Issues With Junos Olive Under Linux Qemu/KVM
I’ve been fighting a bug with Junos Olive VMs running under KVM on a CentOS server for the last few days. I use Olive images now and then for network labs and to test configurations, and lately they’re not running very well at all on my Linux KVM server. Here’s a quick post on the …
Permanent link to this article: https://crypt.gen.nz/2018/07/16/timing-issues-with-junos-olive-under-linux-qemu-kvm/
Using Ansible for Automated Network Testing
The problem with making changes to any decent-sized network, which is running a routing protocol such as OSPF, is that in order to fully verify the change you will need to log into every device in the network and verify that your change has worked. This post shows how Ansible can be used to perform …
Permanent link to this article: https://crypt.gen.nz/2017/11/26/using-ansible-for-automated-network-testing/
ciscoios-acl – A Fail2ban Module for Managing Cisco IOS ACLs
I’ve been using fail2ban to protect a number of services from external attacks. The software works well, but what I wanted to do is to have fail2ban update an ACL on a Cisco IOS router rather then the IPtables on the host itself. Here’s the code and some tips on setting it up.
Permanent link to this article: https://crypt.gen.nz/2017/09/20/ciscoios-acl-a-fail2ban-module-for-managing-cisco-ios-acls/
Dual Stack Policy Rules on Cisco IOS Zone-Based Firewall
The Cisco Zone-based firewall was derived from the old “firewall feature set” and allows the administrator to define firewall rules based on zones, where each zone may contain one or more logical interfaces. Using Cisco’s zone-based firewall isn’t as easy as many other solutions (e.g. Juniper SRX, Cisco ASA), and recently I needed to configure …
Permanent link to this article: https://crypt.gen.nz/2017/09/09/dual-stack-policy-rules-on-cisco-ios-zone-based-firewall/
Restricting Management Access to Fortigate Firewalls
Sometimes it’s just unavoidable that you need to do in-band management of firewalls. This is particularly the case if the firewall is hosted externally – such as within AWS. Here’s a quick recipe on restricting management access to the Fortigate firewall.
Permanent link to this article: https://crypt.gen.nz/2017/08/18/restricting-management-access-to-fortigate-firewalls/
Juniper OSPF and Unexpected Features
I had an interesting situation in a lab environment the other day. It seems Juniper has been tweaking how OSPF works with their routers with some interesting consequences.
Permanent link to this article: https://crypt.gen.nz/2017/08/08/juniper-ospf-and-unexpected-features/
Cisco ASA 5505 – Dual Internet Connections with a Base Licence
The client’s requirements were simple: they had an existing Cisco ASA 5505 with a base and unlimited users licence connected to the Internet with a PPPoE interface over ADSL. They wanted to add more bandwidth and redundancy so decided to add an additional 100mbps fibre link. Is it possible? Read on …
Permanent link to this article: https://crypt.gen.nz/2017/08/01/cisco-asa-5505-dual-internet-connections-with-a-base-licence/
Permanent link to this article: https://crypt.gen.nz/2017/07/01/small-coffee-table/
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