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Trunking, also known as VSAN trunking, is a feature specific to switches in the Cisco MDS 9000 Family. Trunking enables interconnect ports to transmit and receive frames in more than one VSAN, over the same physical link. Trunking is supported on E ports and F ports (See Figure 5-1 and Figure 5-2).
This section includes the following topics:
Trunking the E ports enables interconnect ports to transmit and receive frames in more than one VSAN, over the same physical link, using enhanced ISL (EISL) frame format.
Note Trunking is not supported by internal ports on both the Cisco Fabric Switch for HP c_Class BladeSystem and the Cisco Fabric Switch for IBM BladeCenter.
Trunking F ports allows interconnected ports to transmit and receive tagged frames in more than one VSAN, over the same physical link.
Figure 5-2 represents the possible trunking scenarios in a SAN with MDS core switches, NPV switches, third-party core switches, and HBAs.
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F port trunk with N port.1 |
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The trunking feature includes the following key concepts:
Note The TF-TNP port link between a third-party NPV core and a Cisco NPV switch is established using the EVFP protocol.
The trunking protocol is important for trunking operations on the ports. The protocols enable the following activities:
Table 5-1 specifies the protocols used for trunking and channeling.
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TF-TN port link2 |
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By default, the trunking protocol is enabled on E ports and disabled on F ports. 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.
Note We recommend that both ends of a trunking link belong to the same port VSAN. On certain switches or fabric switches where the port VSANs are different, one end returns an error and the other end is not connected.
By default, trunk mode is enabled on all Fibre Channel interfaces (Mode: E, F, FL, Fx, ST, and SD) on non-NPV switches. On NPV switches, by default, trunk mode is disabled. You can configure trunk mode as on (enabled), off (disabled), or auto (automatic). The trunk mode configuration at the two ends of an ISL, between two switches, determine the trunking state of the link and the port modes at both ends (see Table 5-2 ).
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Tip The preferred configuration on the Cisco MDS 9000 Family switches is one side of the trunk set to auto and the other side set to on.
Note When connected to a third-party switch, the trunk mode configuration on E ports has no effect. The ISL is always in a trunking disabled state. In the case of F ports, if the third-party core switch ACC's physical FLOGI with the EVFP bit is configured, then EVFP protocol enables trunking on the link.
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 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.
Switch 1 (see Figure 5-3) 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 (see Figure 5-3).
For all F, N, and NP ports, the default VF_ID is 1 when there is no VF_ID configured. The trunk-allowed VF_ID list on a port is same as the list of trunk-allowed VSANs. VF_ID 4094 is called the control VF_ID and it is used to define the list of trunk-allowed VF-IDs when trunking is enabled on the link.
If F port trunking and channeling is enabled, or if switchport trunk mode on is configured in NPV mode for any interface, or if NP PortChannel is configured, the VSAN and VF-ID ranges available for the configuration are as described in Table 5-3 .
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Reserved VSANs and they are not available for user configuration. |
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Note If the VF_ID of the F port and the N port do not match, then no tagged frames can be exchanged.
Figure 5-3 Default Allowed-Active VSAN Configuration
You can configure a select set of VSANs (from the allowed-active list) to control access to the VSANs specified in a trunking ISL.
Using Figure 5-3 as an example, you can configure the list of allowed VSANs on a per-interface basis (see Figure 5-4). 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:
Consequently, VSAN 2 can only be routed from switch 1 through switch 3 to switch 2.
Figure 5-4 Operational and Allowed VSAN Configuration
Trunking has the following configuration guidelines and limitations:
The trunking feature has the following general configuration guidelines and limitations:
– 91x4 switches, if NPIV is enabled and used as the NPIV core switch.
– Generation 1 2-Gbps Fibre Channel switching modules.
The trunking and channeling feature includes the following upgrade and downgrade limitations:
If VSAN 4079 is reserved for EVFP use, the switchport trunk allowed vsan command will filter out VSAN 4079 from the allowed list, as shown in the following example:
– If you have created VSAN 4079, the upgrade to NX-OS Release 5.0(1) will have no affect on VSAN 4079.
– If you downgrade after NX-OS Release 5.0(1), the VSAN will no longer be reserved for EVFP use.
In case of TE ports, the VSAN will in be initializing state when VSAN is coming up on that interface and when peers are in negotiating phase. Once the handshake is done, VSAN will be moved to up state in the successful case, and isolated state in the case of failure. Device Manager will show the port status as amber during initializing state and it will be green once VSANs are up.
This example shows the trunk VSAN states of a TE port:
In case of TF ports, after the handshake, one of the allowed VSANs will be moved to the up state. All other VSANs will be in initializing state even though the handshake with the peer is completed and successful. Each VSAN will be moved from initializing state to up state when a server or target logs in through the trunked F or NP ports in the corresponding VSAN.
Note In case of TF or TNP ports, the Device Manager will show the port status as amber even after port is up and there is no failure. It will be changed to green once all the VSAN has successful logins.
This example shows a TF port information after the port is in the up state:
This example shows the TF port information when a server logs in on noninternal FLOGI VSAN. VSAN 2183 is moved to the up state when the server logs in to VSAN 2183.
If you do not configure the VSANs correctly, issues with the connection may occur. For example, if you merge the traffic in two VSANs, both VSANs will be mismatched. The trunking protocol validates the VSAN interfaces at both ends of a link to avoid merging VSANs (see Figure 5-5).
The trunking protocol detects potential VSAN merging and isolates the ports involved (see Figure 5-5).
The trunking protocol cannot detect merging of VSANs when a third-party switch is placed in between two Cisco MDS 9000 Family switches (see Figure 5-6).
Figure 5-6 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 DCNM-SAN helps detect such topologies.
Table 5-4 lists the default settings for trunking parameters.
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This section includes the following topics:
This section describes how to enable the required trunking and channeling protocols.
To enable or disable the Cisco trunking and channeling protocol, follow these steps:
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This section describes how to enable the F port trunking and channeling protocol.
To enable or disable the F port trunking and channeling protocol, follow these steps:
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Enables the F port trunking and channeling protocol (default). |
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To configure trunk mode, follow these steps:
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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. |
To configure an allowed-active list of VSANs for an interface, follow these steps:
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To display trunking configuration information, perform one of the following tasks:
For detailed information about the fields in the output from these commands, refer to the Cisco MDS NX-OS Command Reference.
The show interface command is invoked from the EXEC mode and displays trunking configurations for a TE port. Without any arguments, this command displays the information for all of the configured interfaces in the switch. See Examples 5-1 to 5-3 .
Example 5-1 Displays a Trunked Fibre Channel Interface
Example 5-2 Displays the Trunking Protocol
Example 5-3 Displays Per VSAN Information on Trunk Ports
This example shows how to configure trunking and bring up the TF-TNP link between an F port in the NPIV core switch and an NP port in the NPV switch:
Step 1 Enable the F port trunking and channeling protocol on the MDS core switch:
Step 2 Enable NPIV on the MDS core switch:
Step 3 Configure the port mode to auto, F, or Fx on the MDS core switch:
Step 4 Configure the trunk mode to ON on the MDS core switch:
Step 5 Configure the port mode to NP on the NPV switch:
Step 6 Configure the trunk mode to ON on the NPV switch:
Step 7 Set the port administrative state on NPIV and NPV switches to ON:
Step 8 Save the configuration.