10-6
Cisco ME 3800X and 3600X Switch Software Configuration Guide
OL-23400-01
Chapter 10 Configuring VLANs
Creating and Modifying VLANs
VLAN Configuration Guidelines
•
The switch supports 4094 VLANs.
•
Normal-range Ethernet VLANs are identified with a number between 1 and 1001. VLAN numbers
1002 through 1005 are reserved for Token Ring and FDDI VLANs.
•
The switch does not support Token Ring or FDDI media. The switch does not forward FDDI,
FDDI-Net, TrCRF, or TrBRF traffic.
•
VLAN configurations for VLANs 1 to 1005 are always saved in the VLAN database and in the
switch running configuration file.
•
Configuration options for VLAN IDs 1006 through 4094 (extended-range VLANs) are limited to
MTU. Extended-range VLANs are not saved in the VLAN database.
•
Spanning Tree Protocol (STP) is enabled by default for ports on all VLANs. The switch supports
128 spanning-tree instances. If a switch has more active VLANs than supported spanning-tree
instances, spanning tree can be enabled on 128 VLANs and is disabled on the remaining VLANs. If
you have already used all available spanning-tree instances on a switch, adding another VLAN
creates a VLAN on that switch that is not running spanning tree. If you have the default allowed list
on the trunk ports of that switch (which is to allow all VLANs), the new VLAN is carried on all trunk
ports. Depending on the topology of the network, this could create a loop in the new VLAN that
would not be broken, particularly if there are several adjacent switches that all have run out of
spanning-tree instances. You can prevent this possibility by setting allowed lists on the trunk ports
of switches that have used up their allocation of spanning-tree instances.
If the number of VLANs on the switch exceeds the number of supported spanning-tree instances,
we recommend that you configure the IEEE 802.1s Multiple STP (MSTP) on your switch to map
multiple VLANs to a single spanning-tree instance. For more information about MSTP, see
Chapter 14, “Configuring MSTP.”
•
Although the switch supports a total of 4094 (normal-range and extended-range) VLANs, the
number of routed ports, SVIs, and other configured features affects the use of the switch hardware.
If you try to create an extended-range VLAN and there are not enough hardware resources available,
an error message is generated, and the extended-range VLAN is rejected.
•
In Ethernet virtual connections (EVCs), a bridge domain is similar to a VLAN, except that
bridge-domain membership is determined by which service instances have joined (based on
encapsulation criteria), while VLAN membership is determined by the VLAN tag in the packet. For
more information about bridge domains, see
Chapter 11, “Configuring Ethernet Virtual Connections
(EVCs).”
IEEE 802.10 SAID
100001 (100000 plus the
VLAN ID)
1 to 4294967294
MTU size
1500
1500 to 9198
Translational bridge 1
0
0 to1005
Translational bridge 2
0
0 to1005
VLAN state
active
active, suspend
Table 10-2
Ethernet VLAN Defaults and Ranges (continued)
Parameter
Default
Range
