Cisco Nexus 5000 Series Switch CLI Software Configuration Guide, NX-OS 4.0(1a)N1 (OL-16597-01, January 2009)

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35-2
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
OL-16597-01
Chapter 35 Configuring VSAN Trunking
Information About VSAN Trunking
VSAN Trunking Mismatches
If you misconfigure VSAN configurations across E ports, issues can occur such as the merging of traffic
in two VSANs (causing both VSANs to mismatch). The VSAN trunking protocol validates the VSAN
interfaces at both ends of an ISL to avoid merging VSANs (see Figure 35-2).
Figure 35-2 VSAN Mismatch
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 Nexus 5000 Series switches (see Figure 35-3).
Figure 35-3 Third-Party Switch VSAN Mismatch
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.
VSAN Trunking Protocol
The trunking protocol is important for E-port and TE-port operations. It supports the following
capabilities:
• Dynamic negotiation of operational trunk mode.
• Selection of a common set of trunk-allowed VSANs.
• Detection of a VSAN mismatch across an ISL.
By default, the VSAN 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). Other switches that are directly connected to
this switch are similarly affected on the connected interfaces. If you need to merge traffic from different
port VSANs across a nontrunking ISL, disable the trunking protocol.
Isolated
Switch 1 Switch 2
E port
VSAN 2
E port
VSAN 3
VSAN mismatch
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Switch 1 Switch 3Switch 2
Third-party switches
VSAN 2
E port
VSAN 3
E port
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