ERSPAN v.s Promisc Mode
Dear All,
I've encountered a conflict when try to monitor the traffic in VM deployed on EXSi 5.1 using ERSPAN, ERSPAN requires an IP address on the destined network interface to span the network traffic, but AMD can not be configured to capture those traffic on the destined network interface if IP address is configured, can AMD set the network interface with IP address to capture mode? has anyone experienced such problem before? any suggestion is highly appreciated.
The AMD is installed in VM as well, on different host from the monitored applications.
Thanks a lot!
-Wei
The IP address on the ERSPAN is not necessarily connected to the destination interface of the AMD it is specifically used to terminate the tunnel and can simply belong to the switch itself, you can also then use local SPAN to take the ERSPAN destination port and "mirror" it to the desired output/destination port. As Chris points out the AMD is not capable of terminating ERSPAN, which is why it needs to be terminated on the switch itself. There may be other caveats associated with this which is why you're not seeing any traffic on the AMD, for ERSPAN to work any switch or device the tunnel passes through must be capable of supporting ERSPAN otherwise the header will not be recognized and teh tunnel will not establish correctly. In your set up how do you traverse between the two enclosures, you need to ensure that any devices on that interacting path is ERSPAN capable.
The AMD isn't a ERSPAN destination, so can't receive that traffic.
Now - the following is unsupported/untested, just something I've given some thought to as this has been raised at a customer I deal with.
There are two (that I know of) potential options to add ERSPAN end point capability to a linux server, these may or may not - I never got to a testing phase as I don't have a switch that can do ERSPAN available to me - work.
As always - looking at virtual TAPs is a viable option, though not cost neutral.
They usually have the capbilities to direct themselves to other ports and enclosures and specifically designed to do so, something that isn't always the case with the various SPAN capabilites that initially was a bolt on solution to get insight into switches and now how become a troublesome legacy solution.
