Posts Tagged ‘TCP/IP’

Dell Compellent Enterprise Manager: SQL Server Setup

January 25, 2016

Dell Compellent Enterprise Manager is a separate piece of software, which comes with every Compellent storage array deployment and allows you to monitor, manage, and analyze one or multiple arrays from a centralized management console.

Probably the most valuable feature of Enterprise Manager for an average user is its historical performance statistics. From the Storage Center GUI you can see only real-time data. Enterprise Manager is capable of keeping statistics for up to a year. And can obviously do a multitude of other things, such as assist with capacity planning, allow you to configure replication between production and DR sites, generate reports or simply serve as a single pain of glass interface to all of your Compellent storage arrays.

Enterprise Manager installation does not include an embedded database. If you want to deploy EM database on an existing Microsoft SQL database or install a new dedicated Microsoft SQL Express instance, you need to do it manually. The following guide describes how to install Enterprise manager with Microsoft SQL Server 2012 Express.

SQL Server Authentication

During installation, Enterprise Manager will ask you for authentication credentials to connect to the SQL database. In SQL Server you can use either the Windows Authentication Mode or Mixed Mode. Mixed Mode allows both Windows authentication and SQL Server authentication via local SQL Server accounts.

For a typical SQL Server setup, Microsoft does not recommend enabling SQL Server authentication and especially with the default “sa” account, as it’s seen as insecure. So if you have a centralized Microsoft SQL Server in your network you’ll most likely be using Microsoft Authentication. But for a dedicated SQL Server Express database it’s fine to enable Mixed Mode and use SQL Server authentication.

Make sure to enable Mixed Mode during SQL Server Express installation and enter a password for the “sa” account.

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SQL Server Network Configuration

Enterprise Manager uses TCP/IP to connect to the SQL database over port 1433. TCP/IP is not enabled by default in SQL Server Express, you will need to enable it manually.

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Use SQL Server Configuration Manager, which is installed with the database, and browse to SQL Server Network Configuration > Protocols for SQLEXPRESS > TCP/IP. Enable TCP/IP on the Protocols tab and assign port 1433 to TCP Port field in IPAll section.

Make sure to restart the SQL server to apply the settings and you should now be able to connect Enterprise Manager to the database.

If you get stuck, refer to Dell Compellent Enterprise Manager Installation Guide and specifically the section “Prepare a Microsoft SQL Server Database”. This guide is available in Dell Compellent Knowledge Center.

Switching Logic

June 8, 2012

If you are a junior admin in a small to medium organization then building campus network is simple. Buy several switches, connect desktops and switches together and that’s it. You don’t need any additional configuration, all switches work right out of the box. However, it’s important to understand how packet switching work to troubleshoot problems that can show up later in your work.

Switching works on TCP/IP Layer 2. It means that networking hardware logic operates with MAC addresses. Each time switch receives a packet from any workstation or server it remembers its MAC address and port it was received from. It’s called MAC address or switching table. When somebody wants to send a packet to an other host with particular IP address he sends an ARP request packet. Like tell me who has 12.34.56.78 IP address. Host replies with its MAC address and sender can form a package to it.

Initially switch has empty switching table and does not know where to send packets. When switch doesn’t have particular MAC address in its table it forwards (floods) the packet to all ports. If the next switch doesn’t know this MAC, it further forwards the packet. When packet finally reaches its destination, host answers and switch adds its MAC address into the table.

If you don’t use VLANs, all switches in your network form a broadcast domain. It means that when host sends a broadcast message, ARP request for example, and host with this IP address is powered off then this ARP request will traverse the whole network. It’s important to bear in mind that if you have many hosts in your network, broadcast messages can eventually slow it down. VLANs are usually a solution here.

TCP/IP layers in a nutshell

June 5, 2012

In contrast to the reference OSI networking model (which is not used in any contemporary OS), TCP/IP in its modern updated version has five layers: Application, Transport, Internet, Data Link and Physical.

Application layer deals with everything in regards to high level protocols, like HTTP for example. Say HTTP header with code 200 which means “OK” is a part of the Application layer. This layer is implemented as standard APIs, like WinHTTP API in Windows for example.

Next layer is the Transport Layer. TCP is the most obvious implementation of it and is responsible for error detection. TCP adds a number to each segment, which allows simple packet loss detection on the other end. I believe Unix Socket is an implementation of Transport Layer (as well as Internet Layer, probably) in Unix/Linux.

Internet Layer adds IP addressing and routing to the TCP/IP Networking Model and includes numerous protocols.

Data Link Layer is the Ethernet. It implements MAC addressing, framing and error detection in terms of corrupted data inside a frame.

Physical Layer is focused mostly on transferring data across media. Examples of Physical Layer for Ethernet are: 10BASE-T (ancient coaxial cabling), 100BASE-TX, 1000BASE-T, etc. I guess it is implemented on the NIC driver level.