http://www.cisco.com/en/US/prod/switches/networking_solutions_products_genericcontent0900aecd806c7afe.pdf
Managed Switch :
Managed switches give you more control over your LAN traffic and offer
advanced features to control that traffic.
An unmanaged switch simply allows Ethernet devices to communicate with one another, such as a
PC or network printer, and those are typically what we call “plug and play.” They are shipped with a
fixed configuration and do not allow any changes to this configuration.
An unmanaged switch allows devices to talk to each other, but that is pretty much all
that they do?
Managed switches provide all the features of an unmanaged switch and provide the
ability to configure, manage, and monitor your LAN. And this gives you greater control over how
data travels over the network and who has access to it.
Also, managed switches use protocols such as the Simple Network Management Protocol, or what
we call SNMP, for monitoring the devices on the network. SNMP is a protocol that facilitates the
exchange of management information between network devices. SNMP queries can determine the
health of the network or the status of a particular device. By displaying this data in an easily
understood format, IT managers located at a central site can monitor the performance of the
network and quickly detect and repair network problems without having to physically interact with
the switch.
So SNMP allows me to remotely monitor my network devices, and I don’t have to
go to the site to make changes or troubleshoot the switch?
Ok, let’s talk about costs. I understand that managed switches are more expensive than
unmanaged switches. Why should one pay more for a managed switch?
It’s true that a managed switch is more expensive than an unmanaged switch. However,
there are many additional features you get with a managed switch, such as quality of service,
virtual LANs, redundancy, and port mirroring.
These features help provide control over the traffic traveling over the switch.
Maybe we can take a few minutes to go through each of these features and their benefits so you
can get a better understanding of them.
All right, then, we’ll start with quality of service. Quality of service allows you to prioritize
your network traffic by assigning a higher priority to critical traffic. This helps ensure consistent
network performance and can support delay-sensitive data such as real-time voice. For instance, if
I know I have voice packets traveling over my network, I want to make sure they have the highest
priority so that these voice packets don’t get dropped or delayed and mangle the phone
conversation.
I know what you’re talking about. It’s so frustrating to miss half of what a caller is
saying. What about virtual LANs, VLANs?
VLANs allow a switch to logically group devices together to isolate traffic between these
groups even when the traffic is passing over the same physical switch. This segmentation and
isolation of network traffic help reduce unnecessary traffic. For instance, you can segment traffic
between your finance and marketing groups, so that mission-critical finance information can flow
without delay to the finance users and get bogged down by marketing traffic. This allows better
network performance and in many cases provides an additional level of security.
Another important feature of a managed switch is redundancy. Redundancy provides the ability to
safeguard a network in case a connection or cable fails by providing an alternate data path for
traffic. Managed switches incorporate what is called Spanning Tree Protocol standard, or STP, to
provide path redundancy in the network. Using the spanning-tree algorithm, STP provides
redundant paths while preventing loops that are created by multiple active paths between switches.
STP allows for one active path at a time between two network devices, preventing loops and
establishing the redundant links as a backup to keep integrated systems available and preventing
expensive downtime, which network admins can appreciate.
And, finally, there is port mirroring. In conjunction with a network analyzer, this feature is useful to
diagnose problems. It copies the switch network traffic and forwards it to a single port on the same
switch for analysis by a network analyzer. You can use the analyzer on a monitor port to
troubleshoot network problems by examining traffic on other ports or segments. The benefit of this
is you can troubleshoot problems without taking the network out of service
I can see how they can improve network
performance and give users a more consistent experience with their network.
But why should someone consider using a managed switch?
Each business needs to evaluate the needs of their network. When their network
requirements have evolved to the point where they would like to have some input and control over
the behavior of traffic on their LAN, then it is a good time to consider a managed switch. Also, if you
are planning to deploy advanced services such as wireless LANs or IP telephony in the near future,
managed switches can lay the foundation for these technologies.
Some of the uls may be useful :
http://www.cisco.com/go/switching.
http://www.cisco.com/go/switching
