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This chapter describes how to create a virtual LAN (VLAN) and how the VLANs work.
A VLAN is a group of end stations, independent of physical location, with a common set of requirements. For example, several end stations might be grouped as a department, such as engineering or accounting. If the end stations are located close to one another, they can be grouped into a LAN segment. If any of the end stations are on a different LAN segment, such as different buildings or locations, they can be grouped into a VLAN that has all the same attributes as a LAN even though the end stations are not all on the same LAN segment. The information identifying a packet as part of a specific VLAN is preserved across a Catalyst 5000 series switch connection to a router or other switch.
To define the VLAN, indicate the VLAN number, name, type, maximum transmission unit, security association identifier (SAID), state, ring number, bridge identification number, and number to indicate whether source routing should be set to transparent or bridging. For more information on the commands for creating VLANs, refer to the Catalyst 5000 Series Command Reference publication.
To create a VLAN across a networking domain, perform these steps in privileged mode:
| Task | Command |
|---|---|
| Step 1 Define the VLAN management domain. | set vtp [domain name] [mode mode] [interval interval] [passwd passwd] |
| Step 2 Define the VLAN. | set vlan vlan_num [name name] [type type] [mtu mtu] [said said] [state state] [ring ring_number] [bridge bridge_number] [parent vlan_num] [stp stp_type] [translation vlan_num] |
A VLAN created in a management domain remains unused until it is mapped to Catalyst 5000 series switch ports. The set vlan command maps VLANs to ports. The default configuration has all switched Ethernet ports on VLAN 1. However, you can enter groups of ports as individual entries, for example, 2/1,3/3,3/4,3/5. You can also use a hyphenated format, for example, 2/1,3/3-5. Figure 7-1 shows a local VLAN configuration that groups switch ports into VLAN 10 and
VLAN 20. For more information on the commands for grouping switch ports, refer to the Catalyst 5000 Series Command Reference publication.
To create a VLAN, perform the following task in privileged mode:
| Task | Command |
|---|---|
| Define the VLAN and indicate the included ports. | set vlan vlan_num mod_num/port_num |
After entering the set vlan command, you see this display:
system1> (enable) set vlan 10 2/1-4 VLAN 10 modified. VLAN 1 modified. VLAN Mod/Ports 10 2/1-4 system1> (enable) set vlan 20 2/5-24 VLAN 20 modified. VLAN 1 modified. VLAN Mod/Ports 20 2/5-24
To verify that the VLAN configuration is correct, use the show vlan command. After entering the show vlan command, you see this display:
system1> (enable) show vlan VLAN Mod/Ports ---- --------------------------------------------------------------------- 1 1/1-2 10 2/1-4 20 2/5-24 system1> (enable)
A trunk physically links two Catalyst 5000 series switches or Catalyst 5000 series switches and routers. Trunks carry the traffic of multiple VLANs and allow you to extend VLANs from one Catalyst 5000 switch to another.
Use the set trunk command to configure trunks on ports or to configure the mode for the trunk: on, off, desirable, or auto. Set the trunk to on to make the port a trunk port and off to make the port a nontrunk port. Set the trunk to desirable to make the port a trunk port if the port it is connecting to allows trunking. Set the trunk to auto to make the port a trunk port if the port it is connected to becomes set for trunking. Port 1 on Module 1 is configured as a trunk.
To establish a trunk, you must configure the port on each Catalyst 5000 series switch as a trunk port. For more information on the commands for setting VLAN trunks, refer to the Catalyst 5000 Series Command Reference publication.
To establish trunks, perform these steps in privileged mode:
| Task | Command |
|---|---|
| Step 1 Establish trunks on specific ports. | set trunk mod_num/port_num {on | off | desirable | auto} [vlans] |
| Step 2 Verify that the trunk configuration is correct. | show trunk |
After entering the set trunk command, you see this display:
Console> (enable) set trunk 1/2 5
Port 1/2 allowed vlans modified to 1-5.
Console> (enable) set trunk 1/1 desirable
Port 1/1 mode set to desirable.
Port 1/1 has become a trunk.
To verify the VLAN trunk configuration, use the show trunk command. After entering the show trunk command, you see this display:
Console> (enable) show trunk
Port Mode Status
------- --------- ------------
1/1 desirable trunking
1/2 auto not-trunking
3/1 auto not-trunking
3/2 auto not-trunking
3/3 auto not-trunking
Port Vlans allowed
------- ---------------------------------------------------------------
1/1 1-1000
1/2 1-5
3/1 1-1000
3/2 1-1000
3/3 1-1000
Port Vlans active
------- ---------------------------------------------------------------
1/1 1,55
1/2 1
3/1 1
3/2 1
3/3 1
Console> (enable)
Using VLAN trunks, you can connect switches to each other and to routers using high-speed interfaces. The Catalyst 5000 series switches can multiplex up to 1000 VLANs between switches and routers by using Inter-Switch Link (ISL) on Fast Ethernet, LAN emulation on Asynchronous Transfer Mode (ATM), or 802.10 on FDDI. You can use any combination of these trunk technologies to form enterprise-wide VLANs and choose between low-cost copper and long-distance fiber connections for your trunks.
Load sharing allows VLAN traffic on parallel Fast Ethernet ISL trunks to be split between multiple trunks. By setting Spanning-Tree Protocol (STP) parameters on a VLAN basis, you can define which VLANs have priority access to a trunk and which uses the trunk as a backup when another trunk fails.
In STP, low integer values have the highest priority. Therefore, when you assign spanning-tree port priorities lower than the default value of 32 to VLANs, the traffic of those VLANs travels on the trunk with the lowest integer value. The spanning-tree port priority must be set to the same value at both ends of each trunk on each Catalyst 5000 series switch.
Figure 7-2 illustrates two trunks that are connected to the ports of supervisor engine modules on two Catalyst 5000 series switches. The port cost of carrying VLAN traffic across these trunks is equal.
This splits VLAN traffic between the two trunks and increases the throughput capacity and fault tolerance between Catalyst 5000 switches; Trunk 1 carries traffic for VLANs 8 through 10, and Trunk 2 carries traffic for VLANs 3 through 6. If either trunk fails, the remaining trunk carries the traffic for all of the VLANs.
 | Caution The port cost of a VLAN must be equal on all parallel trunks when setting port priority for load sharing. |
VLAN Trunk Protocol (VTP) is a Layer 2 messaging protocol that maintains VLAN configuration consistency throughout the network. VTP manages the addition, deletion, and renaming of VLANs at the system level. This protocol allows you to manage VLANs on a network-wide basis and make central changes that are automatically communicated to all the other switches in the network without requiring manual intervention at each switch. In addition, VTP minimizes possible configuration inconsistencies that arise when inappropriate changes are made. These inconsistencies can result in security violations because VLANs become cross-connected when duplicate names are used and internally disconnected when VLANs are incorrectly mapped between one LAN type and the other.
VTP is disabled by default on the Catalyst 5000 series ATM switch and must be explicitly enabled. VTP functionality works only with the Network Management Processor (NMP) software version 2.1 or later and ATM software version 3.1 or later.
For more information on the commands for configuring VTP, refer to the Catalyst 5000 Series Command Reference publication.
The following prerequisites apply when configuring VTP:
To configure VTP, perform this task:
| Task | Command |
|---|---|
| Define a VLAN management domain. | set vtp [domain domain_name] [mode mode] [interval interval] passwd passwd] |
After entering the set vtp command, you see this example display:
Console (enable) set vtp Usage: set vtp [domain <name>] [mode <mode> [interval <interval>] [passwd <passwd>] (name: 120-160 characters, mode = (client, server, transparent), interval = 1-300 sec, passwd : 0-64 characters) Console> (enable) set vtp domain catbox mode client interval 160 VTP: domain catbox modified Console> (enable)
To disable VTP, use the set vtp domain domain_name mode transparent command. Setting the mode to transparent does not remove the domain name from the switch, but it disables VTP for that domain. To remove the domain name, use the clear config all command.
Use these commands to verify your VTP configuration:
show vtp domain
Domain Name Domain Index VTP Version Local Mode
----------------- - ---------------- -------------- -------------
Engineering 1 1 client
Advt Interval Vlan-count Max-vlan-storage Config Revision Notifications
--------------- ------------- ---------------- --- -------------------- ---------------
300 5 1023 0 disabled
Last Updater Pruning PruneEligible on Vlans
--------------- --------- ----------------------------------------
172.20.26.151 disabled 2-1000
Console> (enable) show vlan
VLAN Name Type Status Mod/Ports
---- -------------------------- ----- --------- ----------------
1 default enet active 2/1-24
3/1-12
4/13-48
3 vlan3 enet active
55 vlan55 enet active
66 vlan66 fddi active
88 vlan88 tring active
99 vlan99 fddi active
1002 fddi-default fddi active
1003 token-ring-default tring active
1004 fddinet-default fdnet active
1005 trnet-default trnet active
VLAN SAID MTU RingNo BridgeNo StpNo Parent Trans1 Trans2
---- ---------- ----- ------ -------- ----- ------ ------ ------
1 100001 1500 0 0 0 0 0 0
3 100003 1500 0 0 0 0 0 0
55 100055 1500 0 0 0 0 0 0
66 100066 4500 500 0 0 500 0 0
88 100088 1500 0 0 0 0 0 0
99 100099 1500 0 0 0 0 0 0
1002 101002 4500 0 0 0 0 1 1003
1003 101003 4500 0 0 0 0 1 1002
1004 101004 4500 0 1004 0 0 0 0
1005 101005 4500 0 1005 0 0 0 0
Console>
For more information about these commands, refer to the Catalyst 5000 Series Command Reference publication.
Using VTP, each Catalyst 5000 series switch advertises on its trunk ports its management domain, its configuration revision number, and its known VLANs and their specific parameters. A VTP domain comprises a group of one or more interconnected devices that share the same VTP domain name. A switch can be configured to be in one and only one VTP domain.
VTP is comprised of VTP servers and VTP clients that are responsible for maintaining the full list of all VLANs everywhere within the VTP domain. A VTP domain defines the boundary of the specified VLAN. Servers and clients are also responsible for transmitting information through trunks to other attached switches and receiving updates from those trunks.
VTP servers either maintain information in nonvolatile memory or access it using Trivial File Transfer Protocol (TFTP). Using VTP servers, you can modify the global VLAN information using either the VTP Management Information Base (MIB) or the command-line interface (CLI). When VLANs are added and advertised, both servers and clients are notified that they should be prepared to receive traffic on their trunk ports. A VTP server can also instruct a switch to delete a VLAN and disable all ports assigned to it.
The advertisement frames are sent to a multicast address so that they can be received by all neighboring devices, but they are not forwarded by normal bridging procedures. All devices in the same management domain learn about any new VLANs configured in the transmitting device. Because of this process, you need to configure a new VLAN only on one device in the management domain. All other devices in the same management domain automatically learn the configured information. VTP is transmitted on all trunk connections, including ISL, 802.10, and LAN Emulation (LANE).
The presence of a new VLAN is indicated by a VTP advertisement received by a device running VTP. Devices then accept the traffic of the new VLAN and propagate it to their trunks after adding the VTP-learned VLANs to their trunks.
Using periodic advertisements, VTP tracks configuration changes and communicates them to other switches in the network. When a new switch is added to the network, the added devices receive updates from VTP and automatically configures existing VLANs within the network. VTP also dynamically maps VLANs across multiple LAN types with unique names and internal index associations. Mapping eliminates excessive device administration required from network administrators.
VTP establishes global configuration values and distributes the following global configuration information:
The VTP MIB provides the Simple Network Management Protocol (SNMP) instrumentation for the VTP, allowing the reading and setting of specific VTP parameters.
The VLANs on a Catalyst 5000 series switch simplify adding and moving end stations on a network. For example, when an end station is physically moved to a new location, its attributes can be reassigned from a network management station via SNMP or the CLI. When an end station is moved within the same VLAN, it retains its previously assigned attributes in its new location. When an end station is moved to a different VLAN, the attributes of the new VLAN are applied to the end station, according to the security levels in place.
The IP address of a Catalyst 5000 series switch supervisor engine module can be assigned to any VLAN. This mobility allows a network management station and workstations on any Catalyst 5000 VLAN to access directly another Catalyst 5000 series switch on the same VLAN without a router. Only one IP address can be assigned to a Catalyst 5000 series switch; if the IP address is reassigned to a different VLAN, the previous IP address assignment to a VLAN is invalid.
VLANs allow ports on the same or different switches to be grouped so that traffic is confined to members of that group only. This feature restricts broadcast, unicast, and multicast traffic (flooding) to ports only included in a certain VLAN. You can set up VLANs for an entire management domain from a single Catalyst 5000 series switch. A maximum of 250 VLANs can be active at any time.
Figure 7-3 shows an example of VLANs segmented into logically defined networks.
The set vtp and set vlan commands use VTP to set up VLANs across an entire management domain. The default configuration groups all switched Ethernet ports and Ethernet repeater ports as VLAN 1.
By default, Catalyst 5000 series switches are in the no-management domain state until they are configured with a management domain or receive an advertisement for a domain. If a switch receives an advertisement, it inherits the management domain name and configuration revision number. The switch ignores advertisements with a different management domain or an earlier configuration revision number and checks all received advertisements with the same domain for consistency. While a Catalyst 5000 series switch is in the no-management domain state, it is a VTP server; that is, it learns from received advertisements.
The set vtp command sets up the management domain, including establishing the management domain name, the VLAN trunk protocol mode of operation (server, client, or transparent), the interval between VLAN advertisements, and the password value. There is no default domain name (the value is set to null). The default advertisement interval is 5 minutes. The default VLAN trunk protocol mode of operation is set to server.
By default, the management domain is set to nonsecure mode without a password. Adding a password sets the management domain to secure mode. A password must be configured on each Catalyst 5000 series switch in the management domain when in secure mode.
| Caution A management domain does not function properly if the management domain password is not assigned to each Catalyst 5000 series switch in the domain. |
The set vlan command uses the following parameters to create a VLAN in the management domain:
The Catalyst 5000 series switch uses the SAID parameter of the set vlan command to identify each VLAN on an 802.10 trunk. The default SAID for VLAN 1 is 100001, for VLAN 2 is 100002, for VLAN 3 is 100003, and so on. The default MTU is 1500 bytes. The default state is active on an 802.10 trunk.
When translating from one VLAN type (Ethernet, FDDI, Token Ring, FDDI NET, or TR NET) to another, the Catalyst 5000 series switch requires a different VLAN number for each media type.
VLANs consist of the following components:
Because switches and routers directly attach to the backbone, they must be able to transport VLAN information and interoperate with other network components. In response to these requirements, several different transport mechanisms are used for communicating VLAN information across high-performance backbones. Among them are the LANE standard that has been approved by the ATM Forum, Inter-Switch Link (ISL) for Fast Ethernet, and the IEEE 802.10 protocol, which provides VLAN communication across shared FDDI backbones. These different, yet interoperable, VLAN technologies are supported on the Catalyst 5000 series switches. Each allows a single link to carry information from multiple VLANs.
This section contains examples of VLAN configurations for ISLs on Fast Ethernet ports, multiple Catalyst 5000 series switches using STP, and 802.10 protocol on FDDI ports.
Any Fast Ethernet port can be configured as a trunk. Trunks use the ISL Protocol to support multiple VLANs. An ISL trunk is like a continuation of the switching backplane. It allows for the Catalyst 5000 series switch to multiplex up to 1000 VLANs between switches and routers.
The Dynamic ISL (DISL) Protocol dynamically configures trunk ports between Catalyst 5000 series switches; it synchronizes two interconnected Fast Ethernet interfaces into becoming ISL trunks and minimizes VLAN trunk configuration procedures because only one end of a link must be configured as a trunk or nontrunk.
Figure 7-4 shows an example of a Fast Ethernet ISL configuration.
VLAN groups can be set up across multiple Catalyst 5000 series switches if the switches have any two ports of the same VLAN connected, as shown in Figure 7-5.
The trunks and VLANs for the Catalyst 5000 series Switch 1 on the first floor were configured as follows:
System1> (enable) set vtp domain abc
VTP: domain abc modified
System1> (enable) set vlan 10
VTP: vlan addition successful
System1> (enable) set vlan 10 1/1-4
VLAN 10 modified.
VLAN 1 modified.
VLAN Mod/Ports
---- -----------------------
10 1/1-4
System1> (enable) set vlan 20
VTP: vlan addition successful
System1> (enable) set vlan 20 2/5-24
VLAN 20 modified.
VLAN 1 modified.
VLAN Mod/Ports
---- -----------------------
20 2/5-24
System1> (enable) set trunk 1/1-2 on
Port 1/1 mode set to on.
Port 1/2 mode set to on.
System1> (enable)
Mon May 6 1996, 18:22:07 Port 1/1 and 1/2 has become trunk.
System1> (enable) show trunk
Port Mode Status
------- --------- ------------
1/1 on trunking
1/2 on trunking
Port Vlans allowed
------- --------------------------------------------------------------
1/1 1-1000
1/2 1-1000
4/1-2 1-1000
Port Vlans active
------- --------------------------------------------------------------
1/1 1
1/2 1,10,20
4/1-2 1
System1> (enable) show port
Port Name Status Vlan Level Duplex Speed Type
---- -------------- ---------- ---------- ------ ------ ----- -----------
1/1 connected trunk normal full 100 100BaseTX
1/2 notconnect trunk normal full 100 100BaseTX
2/1 notconnect 10 normal half 10 10BaseT
2/2 notconnect 10 normal half 10 10BaseT
2/3 notconnect 10 normal half 10 10BaseT
2/4 connected 10 normal half 10 10BaseT
2/5 notconnect 20 normal half 10 10BaseT
2/6 notconnect 20 normal half 10 10BaseT
.
.
.
2/23 notconnect 20 normal half 10 10BaseT
2/24 notconnect 20 normal half 10 10BaseT
Port Align-Err FCS-Err Xmit-Err Rcv-Err
---- ---------- ---------- ---------- ----------
1/1 0 0 0 0
1/2 0 0 0 0
2/1 0 0 0 0
2/2 0 0 0 0
2/3 0 0 0 0
2/4 0 0 0 0
.
.
.
2/22 0 0 0 0
2/23 0 0 0 0
2/24 0 0 0 0
Port Single-Col Multi-Coll Late-Coll Excess-Col Carri-Sens Runts Giants
---- ---------- ---------- --------- ---------- ---------- ----- -------
1/1 0 0 0 0 0 0 -
1/2 0 0 0 0 0 0 -
2/1 0 0 0 0 0 0 0
2/2 0 0 0 0 0 0 0
2/3 0 0 0 0 0 0 0
2/4 0 0 0 0 0 0 0
.
.
.
2/22 0 0 0 0 0 0 0
2/23 0 0 0 0 0 0 0
2/24 0 0 0 0 0 0 0
Ler
Port CE-State ConnState Type Neig Con Est Alm Cut Lem-Ct Lem-Rej-Ct Tl-Min
---- -------- --------- ---- ---- --------------- ------- --------- ------
Last-Time-Cleared
--------------------------
Mon May 6 1996, 17:59:45
The trunks and VLANs for the Catalyst 5000 series Switch 2 on the second floor were configured as follows:
System2> (enable) Mon May 6 1996, 16:35:47 Port 1/2 has become trunk. System2> (enable) show trunk Port Mode Status ------- --------- ------------ 1/1 auto trunking 1/2 auto trunking Port Vlans allowed ------- -------------------------------------------------------------- 1/1 1-1000 1/2 1-1000 Port Vlans active ------- -------------------------------------------------------------- 1/1 1,10,20,30 1/2 1,10,20,30 System2> (enable) show port Port Name Status Vlan Level Duplex Speed Type ---- -------------- ---------- ---------- ------ ------ ----- ----------- 1/1 connected trunk normal half 100 100BaseTX 1/2 connected trunk normal half 100 100BaseTX 2/1 notconnect 10 normal half 10 10BaseT 2/2 notconnect 10 normal half 10 10BaseT 2/3 notconnect 10 normal half 10 10BaseT 2/4 connected 10 normal half 10 10BaseT . . . 2/21 notconnect 20 normal half 10 10BaseT 2/22 notconnect 20 normal half 10 10BaseT 2/23 notconnect 20 normal half 10 10BaseT 2/24 notconnect 20 normal half 10 10BaseT Port Align-Err FCS-Err Xmit-Err Rcv-Err ---- ---------- --------- ---------- ---------- 1/1 0 0 0 0 1/2 0 0 0 0 2/1 0 0 0 0 2/2 0 0 0 0 2/3 0 0 0 0 2/4 0 0 0 0 . . . 2/19 0 0 0 0 0 0 0 2/20 0 0 0 0 0 0 0 2/21 0 0 0 0 0 0 0 2/22 0 0 0 0 0 0 0 2/23 0 0 0 0 0 0 0 2/24 0 0 0 0 0 0 0 Last-Time-Cleared -------------------------- Mon May 6 1996, 16:04:07 System2> (enable) show port Port Name Status Vlan Level Duplex Speed Type ---- ------------ ---------- ---------- ------ ------ ----- ----------- 1/1 connected trunk normal full 100 100BaseTX 1/2 connected trunk normal full 100 100BaseTX 2/1 notconnect 10 normal half 10 10BaseT 2/2 notconnect 10 normal half 10 10BaseT 2/3 notconnect 10 normal half 10 10BaseT 2/4 connected 10 normal half 10 10BaseT . . . 2/21 notconnect 20 normal half 10 10BaseT 2/22 notconnect 20 normal half 10 10BaseT 2/23 notconnect 20 normal half 10 10BaseT 2/24 notconnect 20 normal half 10 10BaseT Port Align-Err FCS-Err Xmit-Err Rcv-Err ---- ---------- --------- ---------- ---------- 1/1 0 0 0 0 1/2 0 0 0 0 2/1 0 0 0 0 2/2 0 0 0 0 2/3 0 0 0 0 2/4 0 0 0 0 . . . 2/19 0 0 0 0 0 0 0 2/20 0 0 0 0 0 0 0 2/21 0 0 0 0 0 0 0 2/22 0 0 0 0 0 0 0 2/23 0 0 0 0 0 0 0 2/24 0 0 0 0 0 0 0 Last-Time-Cleared -------------------------- Mon May 6 1996, 16:04:07
VLANs can be extended across an FDDI network by multiplexing switched packets over a CDDI/FDDI interface using the 802.10 protocol. Using 802.10, Catalyst 5000 CDDI/FDDI interface links can operate as interswitch trunks that provide broadcast control between configured VLANs. The 802.10 protocol encapsulates a VLAN identifier and packet data according to the IEEE 802.10 specification. CDDI/FDDI interfaces that support 802.10 make selective forwarding decisions within a network domain based upon the VLAN identifier.
The VLAN identifier is a user-configurable 4-byte SAID. The SAID identifies traffic as belonging to a particular VLAN. It also determines which VLAN each packet is switched to the bus.
Refer to Figure 7-6 for an example of configuring FDDI trunks. In this example, the SAID ensures that packets destined for VLAN 1 only reach VLAN 1 after they are transmitted across the FDDI trunks. Refer to Figure 7-7 for an example of an FDDI 802.10 VLAN network configuration.
VTP provides CDDI/FDDI module configuration for 802.10-based VLANs. VTP requires a protocol type (Ethernet, FDDI, or Token Ring) to be configured for each VLAN. A VLAN can only have one type associated with it. Each VLAN type must have its own unique identifier, and translations between different identifiers must be mapped. VTP advertises VLAN translation mappings to all Catalyst 5000 series switches in a management domain.
Catalyst 5000 series switch FDDI/CDDI modules integrate switched Ethernet and Fast Ethernet LANs into the FDDI network. To map an 802.10 FDDI VLAN to an Ethernet VLAN, you must map the 802.10 VLAN SAID to an Ethernet VLAN by mapping an Ethernet VLAN to an FDDI VLAN and assigning a SAID value to the FDDI VLAN.
If a CDDI/FDDI module receives a packet containing a VLAN SAID that maps to a locally supported Ethernet VLAN on the Catalyst 5000 series switch, the CDDI/FDDI module translates the packet into Ethernet format and forwards it across the switch backplane to the Ethernet module. CDDI/FDDI modules filter the packets they receive from reaching the backplane if the VLAN SAIDs in the packets do not map to a locally supported VLAN.
Figure 7-8 illustrates the configuration for forwarding a packet from the Ethernet module port 1 in slot 2 to the FDDI module port 1 in slot 5. For this example, you would specify the translation of Ethernet VLAN 2 to FDDI VLAN 22. FDDI VLAN 22 is then automatically translated to Ethernet VLAN 2. The VLAN SAID must be identical on both FDDI modules. Since 802.10 CDDI/FDDI interface links can operate as interswitch trunks, you can configure multiple VLAN translations over a link.
CDDI/FDDI modules also support one native (nontrunk) VLAN, which handles all non-802.10 encapsulated FDDI traffic. A translation number does not need to be configured for the native VLAN since packets that are forwarded to the native VLAN do not contain VLAN identifiers. To map an Ethernet VLAN to an FDDI native VLAN, you must configure the FDDI port to be on the Ethernet VLAN. To do this, configure the Ethernet VLAN with the module number and port number of the FDDI-native VLAN.
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