NOTE
In bypass mode, ports X5/X7 and X6/X8 are connected to conduct
internal cross-over. The purpose is to facilitate use cases when these
ports are configured with fixed MDI (or fixed MDIX). To support such use
cases, the network design should ensure that cabling also conduct a cross-
over between these ports on adjacent Viper-TBNs. Then there would be
an odd number of cross-overs between adjacent Viper-TBNs, even during
power-loss of an intermediate Viper-TBN.
When bypassing a switch, approximately 5 m (16 ft) of the transmission
range (100 m, 300 ft) is consumed.
As an example, if a network is intended to cope with a single car blackout
scenario and that two Vipers in that case will be by-passed, the total cable
distance through the blackout car to adjacent switches on each side of the
blackout car, should not exceed 90 m (300 ft).
Normally, the Viper can handle longer distances, up to 150 m (500 ft), but
this can not be guaranteed and has to be investigated case by case. Cable
length data is valid for CAT5e cable.
Switch 1
Switch 2
Switch 3
X7
X5
X7
X5
X8
X6
X8
X6
Figure 4. Bypassing of Viper
14
Viper-208-TBN Series
