HP 2424M - Manual (Page 17)

HP ProCurve Switch 4000M / 8000M / 2424M / 1600M Reviewer’s Guide
The HP ProCurve Switch 4000M/8000M/2424M/1600M can also be configured through a single check
box to automatically promote multicast streams that are part of an IGMP group to the high priority
queue, moving these packets through the switch with as little latency as possible. This feature does not
depend on 802.1Q packet tagging, so will work with existing IGMP environments.
More details on IGMP can be found in the paper “HP Switches - Controlling Network Traffic” in the
technical library on HP’s networking web site at
http://www.hp.com/rnd/products/solutions/techlib/techlib.htm .
2.9 IEEE 802.1Q VLAN Support
A Virtual LAN is a logical collection of ports or nodes that belong to a single broadcast/multicast
domain. VLANs were originally devised as a solution to limit the size of any one broadcast domain to
allow scaling of switched environments. With the advent of routing switch solutions, however, use of
VLANs in end user environments is now largely done for network policy or security reasons. In any one
VLAN, network traffic is completely independent of any other VLAN. A local router is required to
interconnect multiple VLANs if traffic is to move between them. Automatic Broadcast Control and
IGMP are compatible with, and work within, the context of each individual VLAN.
The HP ProCurve Switches 4000M/8000M/2424M/1600M support the IEEE 802.1Q standard for VLAN
definition. Until the advent of the 802.1Q standard, identifying which network packets belonged to
which VLANs was done differently by the different vendors, leading to interoperability concerns. The
packet tagging in 802.1Q solves this problem by providing an identification field for VLANs. Now any
device that supports 802.1Q can tell which VLAN a packet belongs to if that packet has been tagged.
This allows packets from different VLANs to travel over the same link interconnecting switches.
Switches from different vendors that adhere to 802.1Q can inter-operate at this level. In addition, since
multiple VLANs can be identified within a single port, multiple VLANs can use the same server on a
single port, as long as that server supports the 802.1Q tagging. As a final benefit, a router that supports
802.1Q can provide routing services between different VLANs through a single link to a switch (also
known as a “one-armed router”).
The HP ProCurve Switch 8000M and HP ProCurve Switch 1600M support up to thirty (30)
10 VLANs per
switch. VLANs are defined by port. A port-based VLAN is one where all packets that are untagged
coming into a particular port are identified with the designated VLAN for untagged packets associated
with that port, providing backwards compatibility to environments that do not support 802.1Q tags.
Each port supports at most one untagged VLAN with the remainder for that port being tagged.
2.10 Port Trunking (Link Aggregation)
Link Aggregation is the industry term for the ability to combine multiple coterminous links (links that
begin at the same point and end at the same point) as one logical link. There are two types supported
by the HP ProCurve Switch 4000M/8000M/2424M/1600M, Cisco's Fast EtherChannel 11 (FEC) and HP
Trunking. Cisco’s Fast EtherChannel defines an automation protocol called PAgP while HP trunking is
manually configured.
Link aggregation allows two HP ProCurve Switch 4000M/8000M/2424M/1600M switches to be
interconnected by 2-to-4 of the same type of links, with all links acting as one higher-speed link. Since
the number of links in a trunk is configurable, the bandwidth is scaleable to the needs of a particular
network. For example, (4) 100Mbps links can be trunked to provide the equivalent of a 400 Mbps
(800 Mbps full-duplex) link between two switches or (4) Gigabit links can be trunked for the equivalent
of a 4 Gigabit (8 Gigabit full-duplex) link. Fiber-optic links can be trunked to interconnect switches
across large campuses.
10 Switch firmware revision C.06.01 or later.
11 EtherChannel ® is a registered trademark of Cisco Systems, Inc.
©1998, 1999, 2000 Hewlett-Packard Co Revision 3.2b – 1/15/2000 Page 17 of 36