> we search for an beaconing error occured in a token-ring network.
> can ethereal grep the beaconing packet??
Only if the token-ring interface on your machine will, at least when put
into promiscuous mode, supply beaconing packets as input packets, and if
the driver on your operating system supplies those packets to whatever
raw packet capture mechanism your OS provides.
Ethereal depends on the raw packet capture mechanism in the OS, and on
the network card and the driver of the card, to supply it with packets;
it cannot do anything the card, driver, and raw packet capture mechanism
won't allow it (or any other sniffing program using them) to do.
I don't know whether the card will supply those packets to the host, or
whether the driver will, when it sees that packet, supply it to the raw
packet capture mechanism (and wouldn't know even if I knew what type of
token-ring interface card you have and what OS you're running) - you'd
have to ask the vendor of the card, and the supplier of the driver for
the card, and perhaps the supplier of the OS (or of the raw packet
capture mechanism, if you're using Windows, where the mechanism isn't
built into the OS, it's the WinPcap add-on) whether they are the case.