[c-nsp] 7940 VLAN's

[Brian Turnbow]

I've never found info regarding the CDP packet headers(or how the below info maps out), but In the mibs for differnet cat switches you may find 

VVID

The Voice Virtual Vlan ID (VVID) to which this
port belongs to.
If the VVID is not supported on the port, this MIB
object will not be configurable and will return
4096.

Setting this MIB object to 4096, the CDP packets
transmitting through this port would not include
Appliance VLAN-ID TLV.

Setting this MIB object to 4095, the CDP packets
transmitting through this port would contain
Appliance VLAN-ID TLV with value of 4095 - VoIP
and related packets are expected to be sent and
received untagged without an 802.1p priority.

Setting this MIB object to 0, the CDP packets
transmitting through this port would contain
Appliance VLAN-ID TLV with value of 0 - VoIP
and related packets are expected to be sent and
received with VLAN-id=0 and an 802.1p priority.

Setting this MIB object to N (1..1000), the CDP
packets transmitting through this port would
contain Appliance VLAN-ID TLV with N - VoIP and
related packets are expected to be sent and received
with VLAN-id=N and an 802.1p priority. 
 
 
Brian

-----Original Message-----
From: Gert Doering [mailto:gert at greenie.muc.de] 
Sent: giovedì 3 febbraio 2005 9.23
To: Brian Turnbow
Cc: Brian Feeny; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] 7940 VLAN's

Hi,

On Thu, Feb 03, 2005 at 08:49:26AM +0100, Brian Turnbow wrote:
> With a cisco switch the vlan gets transmitted with cdp

Does someone happen to have a specification which CDP TLV value is used for that, and how the exact format looks like?  From what I already have, this is likely to be tag 0x0f  ("ATA-186 VoIP VLAN assignment") but I don't know how to extract the VLAN ID from this...

(this goes into tcpdump/print-cdp.c, in case you wonder why I'm asking)

gert
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