High Availability - Draytek Vigor3900 Series User Manual

Enabling firewall applications on your PC may cause the UPnP function not working
properly. This is because these applications will block the accessing ability of some
network ports.
Security Considerations
Activating the UPnP function on your network may incur some security threats. You
should consider carefully these risks before activating the UPnP function.
Some Microsoft operating systems have found out the UPnP weaknesses and hence
you need to ensure that you have applied the latest service packs and patches.
Non-privileged users can control some router functions, including removing and
adding port mappings.
The UPnP function dynamically adds port mappings on behalf of some UPnP-aware
applications. When the applications terminate abnormally, these mappings may not be
removed.
4 . 7 . 4 H i g h A v a
4 . 7 . 4 H i g h A v a
The High Availability (HA) feature refers to the awareness of component failure and the
availability of backup resources. The complexity of HA is determined by the availability
needs and the tolerance of system interruptions. Systems, provides nearly full-time
availability, typically have redundant hardware and software that make the system available
despite failures.
The high availability of the V3900 Series is designed to avoid single points-of-failure. When
failures occur, the failover process moves processing performed by the failed component (the
"Master") to the backup component (the "Slave"). This process remains system-wide
resources, recovers partial of failed transactions, and restores the system to normal within a
matter of microseconds.
Take the following picture as an example. The left V3900 Series is regarded as Master
device, the right V3900 Series is regarded as Slave device. When Master V3900 Series is
broken down, the Slave (backup) device could replace the Master role to take over all jobs as
soon as possible. However, once the original Master is working again, the Slave would be
changed to original role to stand by.
Vigor3900 Series User's Guide
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