HP 2424M - Manual (Page 13)

HP ProCurve Switch 4000M / 8000M / 2424M / 1600M Reviewer’s Guide
Gigabit connections are available. See the white paper on the Gigabit Ethernet Alliance web site for
more wiring details. www.gigabit-ethernet.org
2.2.5 HP ProCurve Switch 2424M Gigabit Stacking Module
The HP ProCurve Switch 2424M Gigabit Stacking Module contains two full-duplex Gigabit ports that
are transceiver based. Both Gigabit-SX and Gigabit-LX transceivers are available for high speed fiber-
optic connections to the backbone or aggregator switches.
The HP ProCurve Gigabit Stacking Kit is also available. The kit contains two specialized full-duplex
Gigabit transceivers and a .5m proprietary cable. This provides a 2 Gbps connection (1 Gbps in each
direction) between switches. The Stacking Kit, used in conjunction with two Stacking Modules
installed in two HP ProCurve Switch 2424Ms provides an inexpensive stacking mechanism. Up to 7
HP ProCurve Switch 2424Ms can be daisy-chained together this way to provide up to 168 ports in the
stack. In any stack there will always be two open transceiver slots for use with Gigabit transceivers to
provide standardized uplink connectivity.
The HP ProCurve Switch 2424M Gigabit Stacking Module does not fit or work in the HP ProCurve
Switch 8000M/4000M/1600M. Modules available for the Switch 8000M/4000M/1600M will, however work
in the switch module slot on the HP ProCurve Switch 2424M.
Pricing for the stacking components is given in the pricing section.
2.3 IEEE 802.3x Flow Control
The HP ProCurve Switches 4000M/8000M/2424M/1600M adhere to the IEEE 802.3x Flow Control
specification. This provides industry standard support for managing heavy port traffic and helps the
switches avoid memory buffer overflows. Flow control is enabled on a port-by-port basis.
2.4 Automatic Broadcast Control
As local LAN environments have grown larger there has been a need to segment the environment to
control and isolate the broadcast domains. Broadcast traffic in particular needs to be controlled
because every node that receives a broadcast packet must interrupt its CPU to determine what to do
with the packet. Traditionally routers have been used to provide this broadcast isolation.
The HP ProCurve Switches 4000M/8000M/2424M/1600M have built it into the switch one of the primary
services routers perform to isolate broadcasts in the form of Automatic Broadcast Control. This
provides separation of broadcast domains to each individual port on the switch. ABC, which has
obvious value in a router-less environment also has value in an environment with routers because the
broadcasts propagate no farther than the individual switch ports, keeping these broadcasts off other
segments between the switch and router.
ABC suppresses broadcasts by participating in the IP & IPX broadcast protocols for path/route
discovery:
• For IP traffic, most broadcasts are generated as ARP requests. The HP ProCurve Switch builds
an ARP cache and can proxy ARP reply back to end nodes directly, keeping the initial ARP
broadcast confined to the segment it went out on.
• For IPX traffic, the switch builds a RIP/SAP table, proxy answering end node NSQs directly,
keeping this type of broadcast traffic on the segment it was generated on. Since IPX uses
broadcast traffic extensively at this level, ABC functionality can substantially reduce overall
broadcast traffic in this environment.
• RIP (IP) and RIP/SAP (IPX) broadcasts are only forwarded to those segments where RIP and
RIP/SAP broadcasts have been heard previously.
©1998, 1999, 2000 Hewlett-Packard Co Revision 3.2b – 1/15/2000 Page 13 of 36