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Cisco Introduces Virtual Switching to Bond Chasses Together

Cisco Systems today announced new technology for two of its modular
switch families: the high-end Catalyst 6500 and mid-range Catalyst 4500.
The company is promoting them both as the next phase of the Campus
Communications Fabric
, a strategy it announced in April, but this is
just branding. The two have no real connection other that they're both
switches and both launched on the same day.

From a technical perspective, the most interesting is the VSS (Virtual
Switching System), an upgrade for the 6500. Enabled via a new Supervisor
Engine module, it enables two 6500 chasses to be bonded together via
10-Gig Ethernet so that they act as one, share a single IP address, MAC
address and virtual backplane. This can make management simpler (half as
many switches to deal with) and cut a routing hop out of a network.


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The two switches can even take advantage of each other's service modules
for features like routing, application acceleration and wireless
management, but there's a big catch here. Although the switches appear
to have a single backplane, they're still only physically connected by a
10-Gbps wire. Each individual 6500 chassis has a backplane of up to 256
Gbps (and at least 32 Gbps), so the 10-Gig Ethernet could easily be a
bottleneck if a lot of traffic from one switch needs to be processed by
a module on the other.

For this reason, the most immediate beneficiaries of VSS are likely to
be Cisco customers who already have two identically-configured 6500
chasses, one sitting idle as a backup. Cisco says that this can
effectively double switching capacity, allowing the spare switch to be
used in production, though as always there's a tradeoff: With no spares,
losing a switch will mean a real reduction in available bandwidth.

The 4500 series gets an across-the-board upgrade with four new chassis
options and three new line cards, collectively known as the 4500-E and
based on new "CenterFlex" ASICs. They boost total switching capacity to
24 Gbps per slot and are fully backward-compatible with previous 4500
modules and chasses, though the new gear is needed for the higher
bandwidth and the new features.


The most notable new feature is better PoE support, with all of the 48
ports on the new 10/100/1000 modules offering enough power (about
18 W)
to run Cisco's dual-radio 802.11n access points. Cisco also
offers a Premium PoE option that boosts power to 30 W, enough for an IP
video camera, though this will require a future software upgrade and
only work for half of the available ports.

RELATED LINKS

bulletCisco's 802.11n AP Announcement Confirms and Surprises
The most unexpected element of Cisco's news is that they will be able to power their dual-radio 802.11n access points using selected models from their Catalyst line of switches.