- Index
- Preface
- Product Overview
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- Configuring Ethernet Interfaces
- Configuring VLANs
- Configuring Private VLANs
- Configuring Rapid PVST+
- Configuring Multiple Spanning Tree
- Configuring STP Extensions
- Configuring Port Channels
- Configuring Access and Trunk Interfaces
- Configuring the MAC Address Table
- Configuring IGMP Snooping
- Configuring Traffic Storm Control
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- Configuring Fibre Channel Interfaces
- Configuring Domain Parameters
- Configuring N-Port Virtualization
- Configuring VSAN Trunking
- Configuring SAN PortChannels
- Configuring and Managing VSANs
- Configuring and Managing Zones
- Distributing Device Alias Services
- Configuring Fibre Channel Routing Services and Protocols
- Managing FLOGI, Name Server, FDMI, and RSCN Databases
- Discovering SCSI Targets
- Advanced Features and Concepts
- Configuring FC-SP and DHCHAP
- Configuring Port Security
- Configuring Fabric Binding
- Configuring Fabric Configuration Servers
- Configuring Port Tracking
Configuring VSAN Trunking
This chapter describes the VSAN trunking feature provided in Cisco Nexus 5000 Series switches.
Information About VSAN Trunking
VSAN trunking enables interconnect ports to transmit and receive frames in more than one VSAN, over the same physical link, using enhanced ISL (EISL) frame format (see Figure 1-1).
VSAN trunking is supported on native Fibre Channel interfaces, but not on virtual Fibre Channel interfaces.
The VSAN trunking feature includes the following restrictions:
- Trunking configurations are only applicable to E ports. If trunk mode is enabled in an E port and that port becomes operational as a trunking E port, it is referred to as a TE port.
- The trunk-allowed VSANs configured for TE ports are used by the trunking protocol to determine the allowed-active VSANs in which frames can be received or transmitted.
- If a trunking-enabled E port is connected to a third-party switch, the trunking protocol ensures seamless operation as an E port.
Additional information about VSAN trunking is covered in the following topics:
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 1-2).
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 1-3).
Figure 1-3 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.
Configuring VSAN Trunking
This section explains how to configure VSAN trunking and includes the following topics:
- Guidelines and Restrictions
- Enabling or Disabling the VSAN Trunking Protocol
- About Trunk Mode
- Configuring Trunk Mode
- About Trunk-Allowed VSAN Lists
- Configuring an Allowed-Active List of VSANs
Guidelines and Restrictions
When configuring VSAN trunking, note the following guidelines:
- We recommend that both ends of a VSAN trunking ISL belong to the same port VSAN. On platforms or fabric switches where the port VSANs are different, one end returns an error, and the other is not connected.
- To avoid inconsistent configurations, disable all E ports with a shutdown command before enabling or disabling the VSAN trunking protocol.
Enabling or Disabling the VSAN Trunking Protocol
To enable or disable the VSAN trunking protocol, perform this task:
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About Trunk Mode
By default, trunk mode is enabled in all Fibre Channel interfaces. However, trunk mode configuration takes effect only in E-port mode. You can configure trunk mode as on (enabled), off (disabled), or auto (automatic). The default trunk mode is on. The trunk mode configurations at the two ends of the link determine the trunking state of the link and the port modes at both ends (see Table 1-1 ).
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Tip
The preferred configuration on the Cisco Nexus 5000 Series switches is that one side of the trunk is set to auto and the other is set to on.
Note When connected to a third-party switch, the trunk mode configuration has no effect. The ISL is always in a trunking disabled state.
Configuring Trunk Mode
To configure trunk mode, perform this task:
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Enables (default) the trunk mode for the specified interface. |
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Configures the trunk mode to auto mode, which provides automatic sensing for the interface. |
About Trunk-Allowed VSAN Lists
Each Fibre Channel interface has an associated trunk-allowed VSAN list. In TE-port mode, frames are transmitted and received in one or more VSANs specified in this list. By default, the complete VSAN range (1 through 4093) is included in the trunk-allowed list.
The common set of VSANs that are configured and active in the switch are included in the trunk-allowed VSAN list for an interface, and they are called allowed-active VSANs. The trunking protocol uses the list of allowed-active VSANs at the two ends of an ISL to determine the list of operational VSANs in which traffic is allowed.
In Figure 1-4, switch 1 has VSANs 1 through 5, switch 2 has VSANs 1 through 3, and switch 3 has VSANs 1, 2, 4, and 5 with a default configuration of trunk-allowed VSANs. All VSANs configured in all three switches are allowed-active. However, only the common set of allowed-active VSANs at the ends of the ISL become operational as shown in Figure 1-4.
Figure 1-4 Default Allowed-Active VSAN Configuration
You can configure a selected set of VSANs (from the allowed-active list) to control access to the VSANs specified in a trunking ISL.
Using Figure 1-4 as an example, you can configure the list of allowed VSANs on a per-interface basis (see Figure 1-5). For example, if VSANs 2 and 4 are removed from the allowed VSAN list of ISLs connecting to switch 1, the operational allowed list of VSANs for each ISL would be as follows:
- The ISL between switch 1 and switch 2 includes VSAN 1 and VSAN 3.
- The ISL between switch 2 and switch 3 includes VSAN 1 and VSAN 2.
- The ISL between switch 3 and switch 1 includes VSAN 1, 2, and 5.
Consequently, VSAN 2 can only be routed from switch 1 through switch 3 to switch 2.
Figure 1-5 Operational and Allowed VSAN Configuration
Configuring an Allowed-Active List of VSANs
To configure an allowed-active list of VSANs for an interface, perform this task:
Displaying VSAN Trunking Information
The show interface command is invoked from the EXEC mode and displays VSAN trunking configurations for a TE port. Without any arguments, this command displays the information for all of the configured interfaces in the switch.
The following example shows how to display the trunk mode of a Fibre Channel interface:
The following example shows how to display the trunk protocol of a Fibre Channel interface:
The following example shows how to display the VSAN information for all trunk interfaces:
Default Settings
Table 1-2 lists the default settings for trunking parameters.
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