Inter-Switch Trunks - Nortel 8300 User Manual

40 VLANs, Spanning Tree, and Static Link Aggregation
Example 1-Traffic flow from a to b1 or b2 Assuming a and b1/b2
are communicating using Layer 2, traffic flows from A to switch E and is
forwarded over the direct link to B. Traffic coming from b1 or b2 to a is sent
by B on one of its MLT ports.
B sends traffic from b1 to a on the link to switch E, and traffic from b2 to a
on the link to F. In the case of traffic from b1, switch E forwards the traffic
directly to switch A, while traffic from b2, which arrived at F, is forwarded
across the IST to E and then on to A.
Example 2-Traffic flow from b1/b2 to c1/c2 Traffic from b1/b2 to c1/c2
is always sent by switch B through the MLT to the core. No matter which
switch (E or F) it arrives at, traffic is sent directly to C through the local link.
Example 3-Traffic flow from a to d Traffic from a to d (and the reverse)
is forwarded across the IST because it is the shortest path. This link is
treated purely as a standard link with no account taken of SMLT and the fact
that it is also an IST.
Example 4-Traffic flow from f to c1/c2 Traffic from f to c1/c2 is sent
directly from F. With return traffic from c1/c2, you can have one active VRRP
Master for each IP subnet. The traffic is passed across the IST if switch C
sends it through the link to E.

Inter-Switch Trunks

SMLT aggregation switches must be connected with an Inter-Switch Trunk
(IST). For example, in
switches" (page
aggregation switches using multilink trunks split between the two
aggregation switches. The implementation of SMLT requires only two
SMLT-capable aggregation switches.
Aggregation switches use the IST to:
•
•
•
•
Because the IST is required for the SMLT, Nortel recommends that you use
multiple links on the IST to ensure reliability and high availability. Nortel
recommends using Gigabit Ethernet links for IST connectivity to provide
enough bandwidth for potential cross traffic.
Configuration — VLANs, Spanning Tree, and Static Link Aggregation using Device Manager
Copyright © 2005-2007, Nortel Networks
.
Figure 10 "8300 switches as SMLT aggregation
39), edge switches B and C are connected to the
Confirm that they are alive and exchange MAC address forwarding
tables.
Carry the SMLT control packets.
Send traffic between single switches attached to the aggregation
switches.
Serve as a backup if one SMLT link fails.
Nortel Ethernet Routing Switch 8300
NN46200-510 03.01 Standard
4.0 27 August 2007