Net Optics iBypass HD - Manual (Page 35)

31
iBypass HD
HA mode—Link failure
In Figure 19, the active router failed and its link to the iBypass Switch went down. The bypass switch reacted to the link
down condition by entering Bypass On mode on the primary link and routing the traffic on the backup link through the
IPS. This action occurred automatically, without any manual intervention by the system administrator. The iBypass Switch
continues to mointor the primary link, and if the down link comes back up (that is, then both sides of the primary link are
connected), the IPS is moved back to the primary link and the backup link goes into Bypass On mode again.
Passive link
Active link
Internet
X
IPS
Active link
Active link
Passive link
Internet
IPS
Backup IPS
Backup IPS
Normal Operation
Operation When Primary Link Fails
Backup IPS
IPS
X
Operation When Primary IPS Fails
Passive link
Internet
Passive link
Active link
Internet
X
Operation When Primary Link
and Primary IPS Fail
Backup IPS
IPS
X
Figure 19: HA mode with a link failure
In some cases, the primary link might fail in a way that doesn't actually lose link. For example, it could fall victim to
a Denial of Service attack, or it could experience a major slowdown for some reason. In usch a case, an administator
or a management tool could switch to using the backup link. In such circumstances, the bypass switch can be forced to
move to the backup link by setting the DBM HA mode force (ha_mode=force) and assigning the link you want as the
primary_link and the tool you want as the primary_tool.
HA mode—IPS failure
In Figure 20, the primary IPS stopped passing Heartbeat packets so the bypass switch rerouted the traffic through the
backup IPS. This action occurred automatically, without any manual intervention by the system administrator. The
bypass switch continues to send Heartbeat packets to the failed IPS, and when it comes back online, the bypass switch
automatically changes the traffic routing so it goes through the primary IPS again.
If both IPSs fail to respond to Heartbeat packets, both bypass switches go into Bypass On mode, opening both links to
traffic flow without going through either IPS.
Passive link
Active link
Internet
X
IPS
Active link
Active link
Passive link
Internet
IPS
Backup IPS
Backup IPS
Normal Operation
Operation When Primary Link Fails
Backup IPS
IPS
X
Operation When Primary IPS Fails
Passive link
Internet
Passive link
Active link
Internet
X
Operation When Primary Link
and Primary IPS Fail
Backup IPS
IPS
X
Figure 20: HA mode with an IPS failure