From: Daniel Cisco Group Study (danielcgs@imc.net.au)
Date: Wed Apr 23 2003 - 18:38:27 GMT-3
So .....
What you're saying is that the reflector port is just a hardware trick or fudge.... We need another dedicated ASIC to do RSPAN.....
Traffic enters a monitored source port and gets send to the reflector port. The reflector port ASIC loops the traffic into the RSPAN vlan, which is carried over your normal trunks on some other port(s), to some other switch(es)....
Is my interpretation correct?
Daniel
-----Original Message-----
From: David Buechner [mailto:dbuechn@attglobal.net]
Sent: Thursday, 24 April 2003 4:54 AM
To: ccielab@groupstudy.com
Subject: RE: 3550 - RSPAN - Reflector Port
Daniel,
Here's how I understand it:
First, let's start with a SPAN session. In SPAN you have some traffic that you're monitoring which is then duplicated on a port local to the switch so
that it is visible to a locally attached device (such as a protocol
analyzer). One of the things that I suspect is important to switch
performance here is that very little processing is done on the duplicated packet - it's just copied to the monitor port.
Now consider the RSPAN scenario. Here, instead of copying the frame to a particular port you need to get it into a particular VLAN and then switch it as new traffic for that VLAN, thus enabling delivery to a remote
destination port. The mechanism on the local switch to do this is the
reflector port. In essence the reflector port acts similarly to a
destination port, only instead of transmitting the packet out the physical port it transmits it out the RSPAN VLAN. I don't know the hardware
intimately, but I would guess that maybe the ASIC in the port can handle
"reflecting" the traffic back to the RSPAN VLAN thereby keeping the switch CPU from having to modify the packet. (I'd be happy to hear from someone who knows the hardware better to see if my WAG is right! :-))
If I'm wrong in any of this I'd very much appreciate commentary!
David
At 07:25 am 4/23/2003 -0600, groupstudy wrote:
>http://www.cisco.com/en/US/products/hw/switches/ps646/products_configuration_guide_chapter09186a00800c6f4c.html
>Pretty good explanation
>
>-----Original Message-----
>From: Daniel Cisco Group Study [mailto:danielcgs@imc.net.au]
>Sent: Wednesday, April 23, 2003 6:19 AM
>To: ccielab@groupstudy.com
>Subject: 3550 - RSPAN - Reflector Port
>
>
>Hi all,
>
>Can someone explain the use / purpose of the reflector port when setting >up RSPAN?
>
>The docs are a bit vague on this.
>
>Thanks in advance.
>
>Daniel
>
>
>
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