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2. Introduction
The 2U Auto Bypass Switch is a multiple port A/B switch that is designed to automatically switch between a normal
network path and a “bypass” or “failover” path for 10/100/1000/10G Ethernet network environments, or multimode
fiber based Ethernet environments. It consists of a 2U high, 19 inch rackmount card cage, a power supply card plus
external 100-240 VAC power supply module (with an option for a second external power supply module for
redundant power), and from 1 to 5 groups of Auto Bypass Switch module cards. Each group of Auto Bypass Switch
modules consists of (2) A/B switch cards and a controller card that provides remote access and control, as well as
automatic control for its pair of A/B switch cards. There are three types of A/B Switch cards. The CAT6 RJ45 A/B
Switch cards support copper based Ethernet environments ranging from 10Base-T up to 10GBase-T. The Fiber
Optic A/B Switch cards are designed for multimode fiber applications and come in two versions – an ST version and
an SC version. The Fiber Optic A/B Switch cards use precision optical mirror mechanisms to switch connections
and are thus completely transparent to rates, protocols, and wavelengths.
Each controller card provides access to user configurable parameters that control an auto-bypass switching function
and an auto-recovery switching function, as well as providing remote switching and monitoring capabilities for each
independent Auto Bypass Switch module group. These features allow the Auto Bypass Switch to be used in a
variety of applications. For example, the Auto Bypass Switch can be used with in-line network monitoring devices,
Intrusion Prevention Systems, etc. to automatically remove these devices from the network for maintenance or
should they fail, while simultaneously providing basic network connectivity via a “bypass” path through the switch.
Other applications include monitoring a “normal” network path and automatically switching to a redundant
“backup/failover” path when a problem in the normal network path occurs, thus providing minimal disruption in
service to the user(s). To prevent “flapping” when intermittent problems exist in the normal path, the auto recovery
function can be disabled to allow the intermittent problem to be corrected while the system continues to use the
backup path. Once the intermittent problem is fixed, the user can then send a command or use the front panel toggle
switch to cause the 2U Auto Bypass Switch to restore the normal network connections.
In order to be able to perform the auto bypass and auto recovery switching functions, the Auto Bypass Switch issues
ICMP echo request (PING) packets from an internal Ethernet node, thru the “normal” network path, to any user
specified external Ethernet node on the user’s network. If the normal path connections go down for any reason, the
Auto Bypass Switch will detect the failure and automatically switch to the bypass/failover path connections while
simultaneously disconnecting the normal path.
The Auto Bypass Switch can automatically switch connection states using its auto bypass and auto recovery
switching functions, or the user can remotely issue switching commands via the switch’s remote control Ethernet
interface or remote control RS232 serial interface. Manual control of the switch is also provided via momentary
contact toggle switches on the front of the unit. These manual toggle switches can be disabled via a front panel
keylock switch.
High reliability non-latching telecommunications relays and non-latching optical switching mechanisms are used in
the A/B Switch Cards that form the switching elements within the Auto Bypass Switch. When powered OFF, these
non-latching relays make a connection between the “A” and the “C” ports on each A/B Switch Card installed in the
Auto Bypass Switch chassis. Thus for most applications, the bypass path will use the “A” ports, and the normal path
will use the “B” ports. With this configuration, should power to the Auto Bypass Switch fail, the bypass path will
automatically be connected (the Auto Bypass Switch connects the A ports to their corresponding C ports) and
remain connected until power is restored. Once power is restored, the Auto Bypass Switch can automatically
reconnect the normal path (switch back to the B-C connection state) if auto recovery mode is enabled. Or the user
can issue a switch command via the RS232 or Ethernet remote control interface. The front panel toggle switch can
also be used to restore the normal connection path.
