Operating instructions

Chapter 7. Cisco Systems IGESM configuration and network integration 161
For this example, we do a simple RSPAN that will redirect all traffic to and from the first
connection to BladeServer1, on to VLAN 500, to be carried over the port-channel link to
6500-1, where it will be directed to a sniffer attached to port g2/2.
Figure 7-17 shows the flow that will occur with the RSPAN configuration being demonstrated
in this example.
One item of note, g0/19, in its role as the reflector port, does not have a cable attached. The
role of a reflector port is to function as an internal loopback so that traffic can be brought from
the port or ports to be monitored and placed onto the RSPAN VLAN (VLAN 500 for this
example) for subsequent transport to a remote monitoring device elsewhere in the network.
Important: The RSPAN reflector ports discussed and tested for this topology were one of
the four external ports on the Cisco Systems IGESM. It is possible to use an
unused blade
server port (for example, g0/14) for the role of the reflector port, but extreme caution should
be used, because using an internal port that had a blade server attached could lead to
unexpected and undesired behavior. All testing for this document was performed using one
of the four external ports (g0/17 - g0/20) as the reflector-port.
Important: As already noted, it is important to understand RSPAN before implementing it
in your environment. One important point often overlooked is that the VLAN being used for
RSPAN must be removed/pruned from any blade server port in the BladeCenter.
Note: The Cisco Systems Intelligent Gigabit Ethernet Switch Module for the IBM Eserver
BladeCenter Software Configuration Guide (which comes with your Cisco Systems
Intelligent Gigabit Ethernet Switch Module) does not currently reflect the correct
procedures for configuring RSPAN on the Cisco Systems IGESM (at a minimum, it
neglects to mention the step to run remote-span on the VLAN being used as the
destination of the RSPAN session). This is under review and should be updated soon to
reflect the correct procedures. This same statement is true in regard to current Cisco
documentation available for using RSPAN on 2950s.
Important: Testing of RSPAN on the Cisco Systems IGESM during the production of this
document showed that issues could arise (unexpected wire-rate traffic streaming) when
using the version of code 12.1(14)AY. This issue is resolved at version 12.1(14)AY1 and
above. We strongly advised that you not use RSPAN with 12.1(14)AY code with RSPAN. If
you have already configured RSPAN and are experiencing the issue of streaming data
associated with 12.1(14)AY, deleting the monitor session using RSPAN will halt this
condition (from config term mode run the command no monitor session x, where x is the
monitor session number configured for RSPAN use).