Distributed server management

Many larger server installations feature multiple CPUs in several different rack locations that require centralised control. For example, the diagram below shows the management of 4 banks of 16 servers by 4 users. However, the largest Black Box® ServSwitchTM installation controls 550 servers. So how do you centralise control without creating a huge mess of wires and extenders?
The answer lies with the ServSwitch Multi, which is designed for multi-user applications, and the ServSwitch Duo, built for single-user applications.
Both of these switches feature on-screen menus for server selection. These let you cascade the switches without having to issue multiple switching commands every time you change to a different server.
They also feature built-in extenders to bridge the gaps between banks of servers and user locations. These extenders allow you to move the switch to the server locations with the help of short cables between servers and switches and long cables between switches and locations.

What is Console Server Management?

Secure Console Servers
Out-of-Band Management with Console Servers
Today's growing networks, server clusters and data centres create new requirements for comprehensive management. Often, when a management protocol like SNMP is used, both management information and data are transmitted within a common network. This is called in-band network management. But, in many cases, this type of management isn't enough. If your data network is down and you need to gain access to the basic computer functions (such as BIOS settings), you may need an out-of-band management solution. The out-of-band route uses channels independent from the data network to transport management information.
Along with KVM switches, the most commonly used devices for out-of-band management are console servers. To use one of these, you typically connect UNIX® based desktop or laptop computers, servers, modems, switches, UPSs, PBX systems and other data centre devices that have a serial RS-232/V.24 port. Through this interface, you can not only display critical system information but also carry out administrative functions, like rebooting or low-level configuring.

Common Console Server Applications

Here are two scenarios that illustrate the advantages of using a console server:
A server that's essential to an e-commerce application fails and, because it's a weekend, there's no one on-site to reboot it. No problem. Management script or cluster soft-ware checks each server in the cluster periodically and, if an error is detected, the at-home admini-strator receives a notification and the same server error message that was sent to the console server. By accessing the console server via the Internet from a home office, the administrator can check the server console messages that were received before the server's failure. In most cases, the failure is caused by a software error and a simple reboot is the remedy. The administrator transmits a reboot sequence to the failed server, enabling it to return to normal operating mode.
A router between the main office administrator and a branch office isn't working, and the branch office network has gone down.
The administrator can't manage the remote network by using SNMP because the network isn't accessible. But if there's a console server in the branch office, the administrator can access the remote network via a dial-in modem connection, making troubleshooting possible. If the entire branch office network is down, the router is probably to blame. Using the console server, the administrator can identify the LAN interface used by the router and redirect office-to-office traffic through another branch office interface.

Security Through a Console Server

You probably want to limit system-critical server and equipment access to authorised personnel only. And, for this, a console server should be able to give you completely encrypted connections, including encrypted authentication characters, socket authentication and IP filtering that limits access to specific network areas.
Look for these common security features in your console server:
Secure Shell (SSH) v.2 : In a normal network, such as that used for Telnet, the session screen and keyboard commands (including authorisation) are transmitted in text mode. But this data can be tapped into as it travels the network. If there's such a risk, a console server should at least provide SSH v.1 or, even better, v.2 encryption protocols for secure data transmission. Socket authentication is vital if the privileges of authorised users should be defined. A user name and a password are required for authentication, and this information is then verified by the local console server database or, if it's a larger installation, a RADIUS server. Dialup security: Apart from the usual security mechanisms like PAP and CHAP, the console server should support SSH encryption and socket authentication for modem/dial-in access. Packet and service filtering enable you to define specific access rules, based on IP addresses, target addresses, port numbers, kind of protocol or other parameters.

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