BladeSystem Virtual Connect

Port monitor on VC flex-10

Trusted Contributor

Port monitor on VC flex-10

Avner was looking for help in a customer situation:


Hello all

A customer problem, has VC Flex-10 and using  this software


The scenario is:


configure port monitor on the external port of vc –flex10 with GBIC 1G copper

configure to collect both receive and transmit traffic from nic 1a of the flex nic on one server.


the problem is:


we didn’t see all the traffic on this external port . (we saw 10percent of the traffic)


Richard provided some help:


Well, unless they had configured NIC 1a on one server to be <= 1Gbit/s they won't be able to see all the traffic via a 1G monitoring port.


That they saw only 10 percent of the traffic suggests the 1A port on the server is still 10 Gbit/s, which means there is no way at all for them to see more than 1/10th the traffic.


Further, since a monitor port can only make use of the bandwidth in one direction (ie is effectively simplex), and since the link to/from the server is full duplex, even if the server NIC *is* constrained to 1Gbit/s, that can be > 1 Gbit/s being shoved at the monitor port - the 1Gbit/s coming out the server port, and then the traffic coming into the server port.  Unless the VC module offers a way to only send portions of the monitored frames out the monitor port, there is no way to get around that short of making the monitoring port faster.  And while I only spent 10 seconds looking at the link above I get the impression it wants to see the full contents of packets.


And still further, even *if* the monitor port could/did have all the traffic sent to/from the server port, there is still the question of whether or not the device connected to the monitor port can keep-up with the traffic flow.



Do you use port monitoring? Is there a best way? What do you do?