When you deploy an SD-WAN 4100/5100 appliance in inline mode, pairs of Ethernet ports on the appliance function as accelerated bridges. Traffic flows into one bridge port and out the other. When two sites with appliances communicate, TCP connections between the sites can be accelerated. Traffic that cannot be accelerated is passed through transparently, as if the appliance were not there.
For maximum reliability, the bridge pairs are equipped with a bypass feature that causes the two ports to be connected to each other should the appliance fail or lose power, allowing traffic to continue flowing even during such an outage.
Inline mode is recommended only for sites where WCCP is not practical, and which have a single WAN link, or have fully independent WAN links that do not use dynamic routing, load-balancing, or fail-over.
For 4000 and 5000 WANOP appliances in release 7.1, the inline mode depends on the NetScaler “add interface Pair” command to isolate bridge traffic, ensuring that traffic from one bridge pair stays on that pair. In previous releases, this was done with VLAN definitions. Appliances that were provisioned with release 7.1 have this feature enabled by default. Appliances that were upgraded to release 7.1 without reprovisioning retain their old configuration. For more information about 4000 and 5000 WANOP appliances, see the Cloud Bridge 7.4 documentation.