gratuitous arps and IP phones

Unanswered Question
Jun 29th, 2007

I have a couple questions about grat. arps and ip phones...

1. If grat arps are enabled for the phone device in CCM, does this mean that the phone accepts or generates grat arps?

2. what is the advantage/disadvantage of having it checked/unchecked?


I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 3.5 (2 ratings)

If Gratuitious ARPS are turned on the Phone, it has the unfortunate effect of causing the Phone to send these ARP broadcasts through both the switch as well as the PC Port. You can imagine what happens. The PC updates its ARP Cache and now assumes there is a 1 hop (both L2 and L3) link possible to the Phone. A subsequent TCP connection request such as the one CVTA tries to make, will go directly to the Phone and not through the switch. And bomb predictably. In most cases the PC ARP Cache will be flushed automagically by Windows every x minutes or so - so there is a good chance that the Switch's ARP broadcast will eventually take hold.


This Discussion