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Defining a network port (cisco switch)

Posted on 2004-08-20
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Last Modified: 2010-04-11
Cisco says: Enabling a network port can reduce flooded traffic on our network. The network report receives all traffic with unknown destination addresses instead of the switch flooding them to all ports in the same VLAN.

Can someone give me an example, of when and how you would use something like this in a basic network?

http://mvpbaseball.cc/post.jpg  is my network
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Question by:dissolved
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by:NetoMeter Screencasts
ID: 11855451
Hi!
I am sorry but I can not understand:

1. What is the problem:
"The network report receives all traffic with unknown destination addresses instead of the switch flooding them to all ports in the same VLAN"
2. I do not see VLANs on your diagram.
3. Which port on which device do you want to enable/disable and what is the reason for that (again what is the problem that you are trying to fix)

I appologize again and definitely do not mean to offend you but I would appreciate if you can be more precise with your post:)

NetoMeter
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Expert Comment

by:lrmoore
ID: 11855754
dissolved, can you post a link to the document that you quoted?
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by:dissolved
ID: 11856147
lrmoore, it was from Ciscos website. I printed it out at work.
It was titled "Using the command line interface" for a 2924xl switch. I looked lrmoore, but couldnt find the link (plus right now I'm on 56k connection yikes)

Just wondering what "defining a port" does. Thats all.
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lrmoore earned 500 total points
ID: 11856334
Assume this is what you're talking about:
http://www.cisco.com/en/US/products/hw/switches/ps607/products_command_reference_chapter09186a008007eb21.html#xtocid128029

Defining one switch port as a network port is another way to reduce the amount of flooding on a VLAN. The Cisco 2900 series switch supports one network port per VLAN. After the network port is defined, all packets with unknown unicast addresses are forwarded to the network port and not flooded to the other ports in the VLAN. This configuration works well in a desktop-switch configuration when many of the ports are connected to workstations. By connecting the network port to a legacy LAN segment where there is a lot of traffic to many different addresses, unknown addresses are flooded to that part of the network where unknown addresses might exist and are not forwarded to connected workstations with well-known addresses.

Beginning in privileged EXEC mode, complete these tasks to define a port to be the network port:

Task  Command  
Step 1 Enter global configuration mode.
 configure terminal
 
Step 2 Define the interface to be configured.
 interface interface
 
Step 3 Define the port as the network port.
 port network
 
Step 4 Return to EXEC mode.
 end
 
Step 5 Verify the entry.
 show running-config
 

What it means: take one port of the switch and configure it as a "network" port using the steps above, and connect that network port to an uplink to connect to the rest of the LAN. It provides some measure of packet storm control. In all my years of working with Cisco products, I've never come across a reason to use it. Primarily because of the prevelant use of TCP/IP at layer 3 instead of broadcast/unicast packets at layer 2. "well-known" addresses are MAC-addresses only. That is the only thing this switch keeps a table of..

Limited flooding is part of the normal switching process. There are situations, however, when continuous flooding can cause adverse performance effects on the network.


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by:dissolved
ID: 11856987
You da man thanks
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