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Cisco Systems IntelligentGigabit Ethernet Switch Modules for the IBMBladeCenter, Software Configuration Guide
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Chapter7 Configuring Interface Characteristics
Understanding Interface Types
Note The physical switch ports can be 10/100/1000 Ethernet ports, 10 0BASE-FX ports, 1000BASE-SX ports,
or small form-factor pluggable (SFP)-module ports. For more information, see the switch hardware
installation guide.
These sections describes these types of interfaces:
•Access Ports, page 7-2
•Trunk Ports, page 7-2
•Port-Based VLANs, page 7-3
•EtherChannel Port Groups, page 7-3
•Connecting Interfaces, page 7-4
Access Ports
An access port belongs to and carries the traffic of only one VLAN (unless it is configured as a voice
VLAN port). Traffic is received and sent in native formats with no VLAN tagging. Traffic arriving on
an access port is assumed to belong to the VLAN assigned to the port. If an access port receives an
IEEE 802.1p- or 802.1Q-tagged packet for the VLAN assigned to the port, the packet is for warded. If
the port receives an IEEE 802.1p- or IEEE 802.1Q-tagged packet for another VLAN, the packet is
dropped, the source address is not learned, and the frame is counted in the No destination statistic.
The switch does not support ISL-tagged packets. If the switch receives an ISL-tagged packet, t he packet
is flooded in the native VLAN of the port on which it was received because the MAC destination address
in the ISL-tagged packet is a multicast address.
Two types of access ports are supported:
•Static access ports are manually assigned to a VLAN.
•VLAN membership of dynamic access ports is learned through i ncoming packets. By default, a
dynamic access port is a member of no VLAN, and forwarding to and from the port is enabled only
when the VLAN membership of the port is discovered. Dynamic access ports on the switch are
assigned to a VLAN by a VLAN Membership Policy Server (VMPS). The VMPS can be a
Catalyst 6000 series switch; the switch does not support the function of a VMPS.
Trunk Ports
A trunk port carries the traffic of multiple VLANs and by default is a member of all VLANs in the VLAN
database. Only IEEE 802.1Q trunk ports are supported. An I EEE 802.1Q trunk port supports
simultaneous tagged and untagged traffic. An IEEE 802.1Q trunk port is assigned a default Port VLAN
ID (PVID), and all untagged traffic travels on the port default PVID. All untagged traffic and tagged
traffic with a NULL VLAN ID are assumed to belong to the port default PVID. A packet with a VLAN
ID equal to the outgoing port default PVID is sent untagged. All o ther traffic is sent with a VLAN tag.
Although by default, a trunk port is a member of every VLAN known to the VTP, you can limit VLAN
membership by configuring an allowed list of VLANs for each trunk port. The list of allowed VLANs
does not affect any other port but the associated trunk port.