S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
Trunking Configuration Guidelines
If you misconfigure VSAN configurations across E ports, you could face consequences such as merging
the traffic in two VSANs (thus causing both VSANs to mismatch). The trunking protocol validates the
VSAN interfaces at both ends of an ISL to avoid merging VSANs (see
In this example, the trunking protocol detects potential VSAN merging and isolates the ports involved.
The trunking protocol cannot detect merging of VSANs when a third-party switch is placed in between
two Cisco MDS 9000 Family switches (see
VSAN 2 and VSAN 3 are effectively merged with overlapping entries in the name server and the zone
applications. The Cisco MDS 9000 Fabric Manager helps detect such topologies. Refer to the Cisco MDS
9000 Family Fabric Manager Configuration Guide.
The trunking protocol is important for E-port and TE-port operations. It supports the following:
By default, the trunking protocol is enabled. If the trunking protocol is disabled on a switch, no port on
that switch can apply new trunk configurations. Existing trunk configurations are not affected—the TE
port continues to function in trunk mode, but only supports traffic in VSANs that it negotiated with
previously (when the trunking protocol was enabled). Also, other switches that are directly connected to
this switch are similarly affected on the connected interfaces. In some cases, you may need to merge
traffic from different port VSANs across a non-trunking ISL. If so, disable the trunking protocol.
Cisco MDS 9000 Family CLI Configuration Guide
Third-Party Switch VSAN Mismatch
Dynamic negotiation of operational trunk mode.
Selection of a common set of trunk-allowed VSANs.
Detection of a VSAN mismatch across an ISL.
OL-16184-01, Cisco MDS SAN-OS Release 3.x