CDP "Trust Bitmap" value?

hakan.topcu · ‎07-20-2011

Hi,

does anyone know, what the "Trust Bitmap" values in a CDPv2 Message is for?

Fragment out of a CDPv2 message:

Trust Bitmap: 0x00

Type: Trust Bitmap (0x0012)

Length: 5

Trust Bitmap: 00

Thanks in advance

Hakan

Peter Paluch · ‎07-20-2011

Hello Hakan,

I would hypothesize that this TLV refers to the setting of the switchport priority extend command. However, please treat this as an unvalidated information. I will test that in our lab tomorrow (hopefully I won't forget that) and get back to you with the results.

Best regards,

Peter

Peter Paluch · ‎07-21-2011

Hello Hakan,

After making a test in our lab, it seems that the Trust Bitmap value is set to 0x1 if the port is configured using the command switchport priority extend trust, and set to 0x0 otherwise. Hence, it seems to me to be an indication to the connected device (usually an IP phone) to trust and not touch any 802.1q CoS marking coming from the attached device (e.g. a PC connected to the phone).

Best regards,

Peter