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Introduction
1-6 Compaq ProLiant BL p-Class GbE Interconnect Switch User Guide
COMPAQ CONFIDENTIAL Codename: Vanilla Part Number: 263680-001 Last Saved On: 4/23/02 9:55 AM
Layer 2 Based Packet Forwarding
The ProLiant BL p-Class GbE Interconnect Switch uses 10/100/1000 Gigabit Layer 2
switching technology. Layer 2 refers to the Data Link layer of the Open Systems
Interconnection (OSI) model, which is concerned with moving data packets across a network
by enforcing Carrier Sense Multiple Access with Collision Detection (CSMA/CD). This layer
performs the following tasks:
• Ethernet packet framing
• MAC addressing
• Physical medium transmission error detection
• Medium allocation (collision avoidance)
• Contention resolution (collision handling)
Layer 2 switching technology allows the GbE Interconnect Switch to look into data packets
and redirect them based on the destination MAC address. This reduces traffic congestion on
the network because packets, instead of being transmitted to all ports, are transmitted to the
destination port only.
IEEE 802.1Q Based Virtual Local Area Network
The ProLiant BL p-Class GbE Interconnect Switch provides support for up to sixty-four
802.1Q Virtual Local Area Networks (VLANs) for server grouping and isolation. A VLAN is
a network segment configured according to a logical scheme rather than a physical layout.
VLANs can be used to combine any collection of LAN segments into an autonomous user
group that appears as a single LAN. VLANs also logically segment the physical network into
different broadcast domains so that packets are forwarded only between ports within the
VLAN. This technology enhances performance by conserving bandwidth and improves
security by limiting traffic to specific domains.
Example 1-1: You may want to isolate the server blade iLO ports from the rest of the
NICs. The iLO ports on Interconnect Switch B can be assigned to their own VLAN and
go to a dedicated uplink or share an uplink using VLAN tagging. Refer to the
“Configuring VLANs” section in Chapter 3 or Chapter 4 for more information.
Spanning Tree Protocol
The GbE Interconnect Switch supports the Spanning Tree Protocol (STP), which allows the
blocking of links that form loops between switches in a network. When multiple links
between switches are detected, a primary link is established. Duplicated links are blocked
from use and become standby links. If the primary link fails, the standby link is activated.
Refer to Appendix D for more information.