Cisco Nexus 6000 Series NX-OS SAN Switching Configuration Guide, Release 7.x
Configuring VSAN Trunking
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Configuring VSAN Trunking

Configuring VSAN Trunking

This chapter describes how to configure VSAN trunking.

This chapter includes the following sections:

Configuring VSAN Trunking

Information About VSAN Trunking

VSAN trunking enable interconnected ports to transmit and receive frames in more than one VSAN. Trunking is supported on E ports and F ports.

VSAN trunking is supported on virtual Fibre Channel interfaces.

The VSAN trunking feature includes the following restrictions:

  • Trunking configurations are applicable only 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.

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 1. 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 2. 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.

Configuring VSAN Trunking

Guidelines and Limitations

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

You can enable or disable the VSAN trunking protocol.

Procedure
     Command or ActionPurpose
    Step 1configure terminal


    Example:
    switch# configure terminal
    switch(config)#
     

    Enters global configuration mode.

     
    Step 2 no trunk protocol enable


    Example:
    switch(config)# no trunk protocol enable
     

    Disables the trunking protocol.

     
    Step 3 trunk protocol enable


    Example:
    switch(config)# trunk protocol enable
     

    Enables trunking protocol (default).

     

    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 the following table).

    Table 1  Trunk Mode Status Between Switches

    Your Trunk Mode Configuration

    Resulting State and Port Mode

    Switch 1

    Switch 2

    Trunking State

    Port Mode

    On

    Auto or on

    Trunking (EISL)

    TE port

    Off

    Auto, on, or off

    No trunking (ISL)

    E port

    Auto

    Auto

    No trunking (ISL)

    E port

    The preferred configuration on the Cisco SAN 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 Inter-Switch Link (ISL) is always in a trunking disabled state.


    Configuring Trunk Mode

    You can configure trunk mode.

    Procedure
       Command or ActionPurpose
      Step 1configure terminal


      Example:
      switch# configure terminal
      switch(config)#
       

      Enters global configuration mode.

       
      Step 2 switch(config)# interface vfc vfc-id
       

      Selects an interface that will be connected to the core NPV switch.

       
      Step 3 interface vfc vfc-id


      Example:
      switch(config)# interface vfc 15
       

      Configures the specified Fibre Channel or virtual Fibre Channel interface.

       
      Step 4 switchport trunk mode on


      Example:
      switch(config-if)# switchport trunk mode on
       

      Enables (default) the trunk mode for the specified interface.

       
      Step 5 switchport trunk mode off


      Example:
      switch(config-if)# switchport trunk mode off
       

      Disables the trunk mode for the specified interface.

      Note   

      Trunk mode cannot be turned off for virtual Fibre Channel interfaces.

       
      Step 6 switchport trunk mode auto


      Example:
      switch(config-if)# switchport trunk mode auto
       

      Configures the trunk mode to auto mode, which provides automatic sensing for the interface.

       

      EXAMPLES

      This example shows how to configure a vFC interface in trunk mode:

      switch# configure terminal
      switch#(config)# vfc 200
      switch(config-if)# switchport trunk mode on
      
      

      This example shows the output for the vFC interface 200 in trunk mode:

      switch(config-if)# show interface vfc200
      vfc200 is trunking (Not all VSANs UP on the trunk)
          Bound interface is Ethernet1/3
          Hardware is Virtual Fibre Channel
          Port WWN is 20:c7:00:0d:ec:f2:08:ff
          Peer port WWN is 00:00:00:00:00:00:00:00
          Admin port mode is E, trunk mode is on
          snmp link state traps are enabled
          Port mode is TE
          Port vsan is 1
          Trunk vsans (admin allowed and active) (1-6,10,22)
          Trunk vsans (up)                       ()
          Trunk vsans (isolated)                 ()
          Trunk vsans (initializing)             (1-6,10,22)
          5 minute input rate 0 bits/sec, 0 bytes/sec, 0 frames/sec
          5 minute output rate 0 bits/sec, 0 bytes/sec, 0 frames/sec
            0 frames input, 0 bytes
              0 discards, 0 errors
            0 frames output, 0 bytes
              0 discards, 0 errors
          last clearing of "show interface" counters never
          Interface last changed at Mon Jan 18 10:01:27 2010

      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 the following figure, 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 below.

      Figure 3. 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 the figure above as an example, you can configure the list of allowed VSANs on a per-interface basis (see the following figure). 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.

      VSAN 2 can only be routed from switch 1 through switch 3 to switch 2.

      Figure 4. Operational and Allowed VSAN Configuration

      Configuring an Allowed-Active List of VSANs

      You can configure an allowed-active list of VSANs for an interface.

      Procedure
         Command or ActionPurpose
        Step 1configure terminal


        Example:
        switch# configure terminal
        switch(config)#
         

        Enters global configuration mode.

         
        Step 2 interface vfc vfc-id


        Example:
        switch(config)# interface vfc 4
         

        Configures the specified interface.

         
        Step 3 switchport trunk allowed vsan vsan-id - vsan-id


        Example:
        switch(config-if)# switchport trunk allowed vsan 35-55
         

        Changes the allowed list for the specified VSAN range.

         
        Step 4 switchport trunk allowed vsan add vsan-id


        Example:
        switch(config-if)# switchport trunk allowed vsan add 40
         

        Expands the specified VSAN to the new allowed list.

         
        Step 5 no switchport trunk allowed vsan vsan-id - vsan-id


        Example:
        switch(config-if)# no switchport trunk allowed vsan 61-65  
         

        Deletes the specified VSAN range.

         
        Step 6 no switchport trunk allowed vsan add vsan-id


        Example:
        switch(config-if)# no switchport trunk allowed vsan add 40
         

        Deletes the expanded allowed list.

         

        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:

        switch# show interface vfc33
        
        vfc33 is up
            Hardware is Fibre Channel, SFP is short wave laser w/o OFC (SN)
            Port WWN is 20:83:00:0d:ec:6d:78:40
            Peer port WWN is 20:0c:00:0d:ec:0d:d0:00
            Admin port mode is auto, trunk mode is on
        
        ...

        The following example shows how to display the trunk protocol of a Fibre Channel interface:

        switch# show trunk protocol
        
        Trunk protocol is enabled

        The following example shows how to display the VSAN information for all trunk interfaces:

        switch# show interface trunk vsan 1-1000
        
        vfc31 is not trunking
        ...
        vfc311 is trunking
            Belongs to san-port-channel 6
            Vsan 1 is up, FCID is 0xef0000
            Vsan 2 is up, FCID is 0xef0000
        ...
        san-port-channel 6 is trunking
            Vsan 1 is up, FCID is 0xef0000
            Vsan 2 is up, FCID is 0xef0000

        Default Settings for VSAN Trunks

        The following table lists the default settings for VSAN trunking parameters.

        Table 2  Default VSAN Trunk Configuration Parameters

        Parameters

        Default

        Switch port trunk mode

        On

        Allowed VSAN list

        1 to 4093 user-defined VSAN IDs

        Trunking protocol

        Enabled