H3C S12500 Series Configuration Manual page 20

TRILL distribution trees support Equal Cost Multiple Path (ECMP), also known as multicast ECMP. When
multicast ECMP is disabled, because the topologies of TRILL distribution trees are different, traffic can be
load shared. However, equal-cost links are not used for load sharing.
When N equal-cost links exist in the network, each TRILL distribution tree selects the link with the largest
pseudo-node ID for forwarding packets. As shown in
and RB 3. Assume the link directly connecting RB 1 to RB 3 has the largest pseudo-node ID. Both the TRILL
distribution tree rooted at RB 3 and the TRILL distribution tree rooted at RB 4 select the link.
Figure 6 Multicast ECMP
RB 1
Cost = 1
When multicast ECMP is enabled, TRILL assigns equal-cost links to different TRILL distributions trees. This
improves the load sharing performance.
When N equal-cost links exist in the network, each TRILL distribution tree selects an equal-cost link for
forwarding packets through J mod N in root bridge priority order. J is the priority sequence number of a
multicast tree and starts from 0.
As shown in Figure 6:
The link directly connecting RB 1 to RB 3 is assigned to the TRILL distribution tree rooted at RB 3.
•
The link RB 1-RB 2-RB 3 is assigned to the TRILL distribution tree rooted at RB 4.
•
To configure the TRILL distribution trees:
Step
1. Enter system view.
2. Enter TRILL view.
3. Set a priority for the RB.
4. Configure the number of
TRILL distribution trees that
the RB wants all RBs to
compute.
5. (Optional.) Enable multicast
ECMP.
Figure
RB 3
RB 2
Command
system-view
trill
tree-root priority priority
trees calculate count
multicast-ecmp enable
14
6, two equal-cost links exist between RB 1
RB 4
Remarks
N/A
N/A
The default setting is 32768.
The default setting is 1.
By default, multicast ECMP is
disabled.
Make sure the multicast ECMP
status is the same on all RBs in the
TRILL network. Otherwise,
multicast, broadcast, and
unknown unicast frames might
fail to be forwarded.