The ramblings of a computer geek
In the previous article we discovered that iBGP requires a topology and usage that ensures that our exchange of routes between routers is not stopped by the iBGP rule: “A route learned via iBGP must not be advertised to another iBGP peer.” We came across this problem in the previous article where although in normal operational the routes were being … Read more
We’ll continue to explore Internal BGP (iBGP) in this next part of our deployment. We are going to be deploying another route in the AS Blue 65001. Remember that eBGP is used between AS and iBGP is used within an AS. Be aware however, that this lab topology is flawed in terms of its configuration, but it shows up … Read more
Internal BGP (iBGP) is the next part of our deployment. We are going to be deploying two routers within one of the AS, Blue 65001. Remember that eBGP is used between AS and iBGP is used within an AS. So in this case our second router, Router B, will be linked to Router A via a single link, these … Read more
You can submit commands into an EC2 instance via SSM (Secure Systems Manager), rather than having to open SSH to the machine. From within an authenticated session using AWS CLI on your workstation machine, you can remotely send commands to be run within the instance itself. The commands will typically be run as “root” within … Read more
Here’s an interesting one I came across today, there exists a problem whereby replacing a certificate on a Microsoft Exchange 2016 or 2019 won’t work if the Issuer and Subject of the new certificate happen to be the same as the old certificate (you are trying to replace). You’d expect most likely that when you … Read more
What to do when your self-signed certificate for Microsoft Exchange 2016 expires, Microsoft provide some good guidance about this: https://learn.microsoft.com/en-us/exchange/architecture/client-access/renew-certificates?view=exchserver-2019 You might see errors such as this when you’re trying to administer via PowerShell: You’ll have permissions so the error is a red herring, what is actually happening is you’re attempting to perform an operation … Read more
The first part is a basic deployment of BGP between two routers (Router A and Router B) with a single point to point link. In this example, each router is within its own AS (Autonomous System). Therefore any routes exchanged between each AS are eBGP (external BGP) routes. Routes exchanged within an AS are known … Read more
Although there are a few ways to do it, here is an example of how you can use the null_resource to make Terraform wait for an EC2 instance to be ready before continuning. In this example we have an EC2 instance called mgmt_host which will using the “trigger” set the Terraform into a loop to … Read more
So you have an EC2 instance you’ve deployed from Terraform, but as part of the run of your template you want to run some other commands. Sure, you can use the “user data” section to run commands at deployment time, but what if you want to run something later on? Well, you can use a … Read more
The time of on-premise Microsoft Exchange servers is beginning to draw to a close, although the Microsoft Exchange Server SE will continue, its feature complete essentially as of Exchange Server 2019, although there may be the odd minor changes here and there. Based on that replacing the certificate is a common task, the following instructions … Read more