The ramblings of a computer geek
The Microsoft Exchange Poison Queue is a little known queue on an on-premise Microsoft Exchange Server, maybe I’ve been lucky, but I’ve only seen emails end up here once in my time using Exchange Server which goes back to Exchange 5.5. However this week, we observed some messages going into the Poison Queue which were … Read more
Was working recently with some colleagues on their coursework, where they had a need to configure a Cisco ASA Firewall to prepare a network topology that met certain criteria. They were using Cisco Packet Tracer, but were having a problem creating sub-interfaces (for each VLAN), it seemed that Cisco Packet Tracer (or the current version … Read more
During the preparation for a migration of the email service to Microsoft 365 Exchange Online, we were preparing a small test environment so we could step through what is required to faciltiate the links between Microsoft Active Directory, Microsoft Exchange on-premise and the Microsoft 365 cloud environment that includes Microsoft Exchange Online cloud hosted email. … Read more
We had a bit of an oddity on an Extreme Networks SwitchEngine (XOS) switch running: 32.7.1.9patch1-26, devices connecting to a specific VLAN that should be authenticated by Netlogin (NAC) via radius were failing giving the error below. Checking the switch, the VLAN very much existed, so it was a mystery why it said it wasn’t. … Read more
If you have a VLAN which used as the source of multicast streams there are considerations on how it is used specifically when you are “stretching” that VLAN across the fabric, i.e. you have the VLAN and router(s) for that VLAN on a particular distribution switch pair, but then you have the VLAN stretched across … Read more
To get a list of current AWS Aurora MySQL (compatible) Database Engines you can use the following command from the AWS CLI: So you’ll get an output like: At the time of writing (05/02/25) the recommended/default version is: 8.0.mysql_aurora.3.05.2, but remember that the list of Database Engines that are provided will include ones that are … Read more
Sometimes it can be handy to connect into an IMAP(s) server to verify it is working as expected, or to view emails via a command line interface. In this example I’m connecting to a Microsoft Exchange 2016 Server with IMAP enabled, specifically IMAPS, so running on port 993. Connect and Login Firstly we need to … Read more
Multicast can be very complex, its sometimes handy to be able to just test multicast yourself between two machines on the network. VLC Media Player allows you to do this quite easily. Configure Server (Sender) Firstly get yourself a video file you wish to multicast stream out across your network and place it on the … Read more
Multicast is a networking method used to efficiently transmit data to multiple recipients simultaneously. Unlike unicast (one-to-one) and broadcast (one-to-all) communication, multicast is a one-to-many or many-to-many method where data is sent only to devices that are interested in receiving it, rather than to all devices on a network. In multicast, devices that want to … Read more
You can use EC2 Instance Session Manager to give you direct console access without the need for an SSH connection direct to the instance (which can cause some security issues), instead you can get the same kind of access via the AWS CLI. These instructions assume you have an EC2 instance already setup and working … Read more