How Trill Works - H3C S6800 Series Configuration Manual

Figure 1 TRILL data frame format
0
Outer
Ethernet
header
TRILL
header
Inner
Ethernet
header
Payload
Table 1 describes the fields in the TRILL header.
Table 1 TRILL header fields
Field
Ethertype
V
R
M
Op-Length
Hop Count
Egress RB Nickname
Ingress RB Nickname
Options

How TRILL works

TRILL establishes and maintains adjacencies between RBs by periodically advertising Hello frames,
distributes LSPs among RB neighbors, and generates an LSDB for all RBs in the network. Based on
the LSDB, each RB uses the SPF algorithm to calculate forwarding entries destined to other RBs.
Outer Destination MAC Address
Ethertype = 802.1Q
Ethertype = TRILL
Egress RB Nickname
Inner Destination MAC Address
Ethertype = 802.1Q
Ethertype of Original Ethernet Payload
Description
The Ethertype is fixed to 0x22F3.
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.
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.
Multidestination attribute:
•
0—Known unicast frame.
•
1—Multidestination frame (multicast, broadcast, or unknown unicast frame).
Length of the Options field. 0 indicates that the Options field does not exist.
Hop count, which is used to avoid loops. An RB drops a TRILL frame whose hop
count is decremented to 0.
Nickname of the egress RB.
Nickname of the ingress RB.
Options field. This field exists when the Op-Length field is non-zero.
16
Outer Source MAC Address
Outer VLAN Tag Information
V R
Options
Inner Source MAC Address
Inner VLAN Tag Information
Original Ethernet Payload
New FCS
2
M Op-Length Hop Count
Ingress RB Nickname
32