Cisco Catalyst 2950 Command Reference

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Catalyst 2950 and Catalyst 2955 Switch Command Reference
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Chapter 2 Catalyst 2950 and 2955 Cisco IOS Commands
switchport trunk
• vlan-atom is either a single VLAN number from 1 to 4094, a list of nonconsecutive VLANs, or a
continuous range of VLANs described by two VLAN numbers, the lower one first, separated by a
hyphen.
For a list of nonconsecutive VLAN IDs, separate the VLAN IDs with a comma. Do not enter a space
after the comma.
For a continuous range of VLAN IDs, use a hyphen to designate the range. Do not enter a space
before or after the hyphen.
These are examples showing how to specify one or more VLANs:
– Single VLAN—101
– List of nonconsecutive VLANs—10,12,14,16,18
– Continuous range of VLANs—10-15
– List of VLAN continuous ranges—10-15,20-24
– List of nonconsecutive VLANs and VLAN continuous ranges—8,11,20-24,44
Defaults VLAN 1 is the default native VLAN ID on the port.
The default for all VLAN lists is to include all VLANs.
Command Modes Interface configuration
Command History
Usage Guidelines A trunk port cannot be a secure port or a monitor port. However, a static-access port can monitor a
VLAN on a trunk port. The VLAN monitored is the one associated with the static-access port.
Allowed VLAN:
• To reduce the risk of spanning-tree loops or storms, you can disable VLAN 1 on any individual
VLAN trunk port by removing VLAN 1 from the allowed list. This is known as VLAN 1
minimization. VLAN 1 minimization disables VLAN 1 (the default VLAN on all Cisco switch trunk
ports) on an individual VLAN trunk link. As a result, no user traffic, including spanning-tree
advertisements, is sent or received on VLAN 1.
When you remove VLAN 1 from a trunk port, the interface continues to send and receive
management traffic, for example, Cisco Discovery Protocol (CDP), Port Aggregation Protocol
(PAgP), Link Aggregation Control Protocol (LACP), Dynamic Trunking Protocol (DTP), and
VLAN Trunking Protocol (VTP) in VLAN 1.
• The no form of the allowed vlan command resets the list to the default list, which allows all VLANs.
Native VLANs:
• All untagged traffic received on an IEEE 802.1Q trunk port is forwarded with the native VLAN
configured for the port.
Release Modification
12.1(6)EA2 This command was introduced.
12.1(14)EA1 The allowed vlan vlan list add, remove, and except keywords were
modified to accept the VLAN 1 and VLANs 1002 to 1005 values.

Cisco Catalyst 2950 Specifications

General

Forwarding Bandwidth	8.8 Gbps
Switching Capacity	13.6 Gbps
Forwarding Rate	6.6 Mpps
Weight	3.6 kg
RAM	16 MB
Flash Memory	8 MB
Operating Humidity	10% to 85% non-condensing
Uplink Ports	2 x 10/100/1000Base-T
Dimensions	4.4 cm x 44.5 cm x 24.2 cm
Remote Management Protocol	SNMP, Telnet, HTTP
Features	Quality of Service (QoS), VLAN support
Compliant Standards	IEEE 802.3, IEEE 802.3u, IEEE 802.1D, IEEE 802.1Q, IEEE 802.1p
Status Indicators	system
Operating Temperature	0 to 45°C
Ports	24 x 10/100 Ethernet ports
MAC Address Table Size	8, 192 entries
Power Supply	Internal 100-240V AC, 50-60Hz