Vsan Trunking Mismatches; Vsan Trunking Protocol - Cisco Nexus 5000 Series Configuration Manual

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 the following figure).
Figure 16: 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 SAN switches (see the following figure).
Figure 17: Third-Party Switch VSAN Mismatch
VSAN 2 and VSAN 3 are effectively merged with overlapping entries in the name server and the zone
applications. 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.
Cisco Nexus 5000 Series NX-OS SAN Switching Configuration Guide, Release 5.2(1)N1(1)
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Configuring VSAN Trunking
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