2
Figure 1 TRILL data frame format
Table 1 describes the fields in the TRILL header.
Table 1 TRILL header fields
Field Descri
tion
Ethertype The Ethertype is fixed to TRILL.
V
Version number, which is 0. When an RB receives a TRILL frame, it checks the V
field and drops the frame if the V field is not 0.
R
Reserved for future extension. An ingress RB sets the R field to 0 when adding a
TRILL header. Transit RBs and egress RBs ignore the field.
M
Multidestination attribute:
• 0—Known unicast frame.
• 1—Multicast, broadcast, or unknown unicast frame.
Op-Length Length of the Options field. 0 indicates that the Options field does not exist.
Hop Count
Hop count, which is used to avoid loops. An RB drops a TRILL frame whose hop
count is decremented to 0.
Egress RB Nickname Nickname of the egress RB.
Ingress RB Nickname Nickname of the ingress RB.
Options Options field. This field exists when the Op-Length field is non-zero.
