[rbridge] How is an IS-IS packet differentiated from layer 3 IS-IS, and TRILL-encapsulated data packets?

[Erik Nordmark]

Silvano Gai wrote:

> The advantage of using a reserved bit is that the frame with Ethertype = TRILL already go through DR blocked ports. The non-TRILL IS-IS frames will have Ethertype = ISIS and will be dropped by DR blocked ports.

I don't know if this matters, but AFAIK (and after checking RFC 1142), 
there is no Ethertype for IS-IS. Instead IS-IS uses a 802.3 header (i.e. 
a length field instead of an Ethertype field) followed by 3 bytes of LLC 
header with the SAP 0xFE. Thus the 3 bytes after the length field is 03 
FE FE.

    Erik