Posts in Network

Availability Group Endpoint URL Firewall Gotcha

A few days ago I was working on changing the Endpoint URL and Port for a 2016 SQL Server Availability Group to use a private network interface. We wanted this so we could have the Synchronizing (or Mirroring) traffic have its own dedicated network, which would keep it away from the network traffic of client connections to the database server. This would help increase the throughput of data to and from the databases in the Availability Databases list.

Our setup is a straight forward Windows Cluster with two Nodes. We have two stand alone SQL Server Instances running on these Nodes. Each Instance has an Availability Group defined with one Node the Primary Replica and the other Node the Secondary Replica. We run the Replicas in Synchronous Commit Availability Mode with Automatic Failover. All connections are allowed to the Primary Role and the Readable Secondary is set to no.

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How to get Linux hosts with DHCP IP addresses to show up in Microsoft DNS automatically

This blog post outlines a little trick we use to get Linux-based hosts on a network to show up in Microsoft-based DNS… automagically. This self-registration with DNS usually “just works” in a homogeneous Windows network (famous last words!)– so many folks take it for granted until they need something from the Linux ecosystem. Without setting this up, your options are either A) refer to said machines by IP address only, or B) manually add their hostnames and IPs into DNS, and manually keep those records updated. Keep reading…

Using Wireshark to View/Track SQL Server Browser Traffic

Setting up a Wireshark filter to view only SQL Server Browser traffic is fairly simple, once you are familiar with the tools. All SQL Server Browser traffic uses UDP port 1434 as either the origin or destination. For a server with multiple instances, the Browser helps direct client connections to the correct instance. Using Wireshark to take a detailed look at this network activity can help shed some light on client connection issues that would otherwise be a real nightmare.
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