Depends on how you want to simulate the frame. A cisco router can act as a
switch, but it doesn't FECN or BECN...so, if you're actually testing newer
features like Frame Relay Traffic Shaping you would be hard pressed to see
any benefit 8^). However, quick and dirty emulation can be done with an old
cisco router (I personally use an AGS+ running 10.3 - the highest it can go
- with a ton of serial ports).