Ole Drews Jensen wrote:
> The question is, what would be least resource-waste to use as a
> trunking link : ISL or 802.1Q???
Strictly resource wise, clearly 802.1Q, provided all your devices
support it (earlier cisco stuff doesn't).
There was a BUGTRAQ report some time ago, however, reporting that due to
the frame modification of the 802.1Q packets, that it was possible to
rather trivially inject 802.1Q frames into the network destined for any
arbitrary VLAN. This isn't as easy with ISL as it is harder to
fake/generate a raw ISL packet. I don't know if this has been fixed or
deemed a low-risk as I haven't heard anything else about it in months.
In both cases, particularly ISL, you should realize that with many
switches your interface statistics and SNMP MIBs will incorrectly report
"giants" as line errors when in fact this is due to the addition of the
ISL framing pushing the frame size > the media MTU.
Unless you have a "highly specialized ASIC" that is aware of this, your
typical stock ASIC will report them as giants, although they are
processed normally by the switch. The 29nnXL IOS-based switches suffer
from this "false error reporting" although the "classic" Catalysts
(2900, 5000, 5500) do not.
Jeff Kell <[EMAIL PROTECTED]>
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