uplinkfast & spoofing mac-address

[Ziga M]

Hi all, I'm reading about proprietary uplinkfast function and it's saying that when switch will switch to blocked port, it will send some "dummy" multicast packets to "advertise" that mac addresses are now reachable on this previously-blocked-port. I checked this function in lab, but I didn't noticed any multicast packets. After I unplug the cable it's very quick - 1 ping is lost, not more. But how does it know where to send pings after blocked port is unblocked? Without that multicast packet, I assume it's broadcasted on all active ports and 1 will reply... Correct?

[Fabienne Stephanoff]

Hello Ziga,

In your lab, are you looking for dummy packets to 01-00-0c-cd-cd-cd ?

[Ziga M]

Hello,

Yes, that's the one ... I was trying a little more and noticed that when I unplug the "working cable" (and second switch quickly switch to prevoiusly-blocked-port), first ping will be broadcasted on all ports on the first switch, because it doesn't know where the mac address is. So it's anohter proof that second switch never sent any "dummy multicast" packet. I'm using 3550 swithes, maybe the IOS or hardware is a problem