Specifications

24 Barracuda Link Balancer Administrator’s Guide
Creating Custom Applications
Use the Policy > Applications page to view and define applications that can be used in firewall and
Quality of Service rules. An application is a combination of a protocol and one or more ports. You
can create new applications or use the predefined ones, such as DNS, email, and HTTP.
Managing Bandwidth
The Barracuda Link Balancer allows you to prioritize and control incoming and outgoing traffic and
link usage in a variety of ways.
This section covers the following topics:
Link Usage for Inbound and Outbound Traffic ................................. 24
Creating Bandwidth or Quality of Service (QoS) Rules.................... 25
Link Usage for Inbound and Outbound Traffic
Outbound Link Balancing
By default, when outbound traffic from a client IP address going to a new destination IP address is
detected, the weights of the links are compared and the link with the highest weight is used. The
weight of a link is the available capacity based on configured link speed and current usage. The weight
for each primary and backup WAN link is calculated on an ongoing and frequent basis.
Inbound Link Balancing
Inbound link balancing and failover are available only if the Barracuda Link Balancer acts as an
authoritative DNS server for domains behind it.
When the Barracuda Link Balancer receives a DNS query for a hosted domain, it returns the IP
address of a WAN link which the client then uses to reach the hosted domain. The algorithm used to
select the returned WAN link is the same as the algorithm used for outbound link balancing.
Grouping WAN Links for Inbound and Outbound Traffic
You can change how frequently WAN links are used by assigning each link to one of three groups for
both inbound and outbound traffic. This feature allows you to reserve links for certain types of traffic
or to use higher cost links only if the lower cost links fail or become saturated.
The supported usage groups are:
• Primary links — used first for link balancing.
• Backup links — used only if the primary links are down or if they become saturated. If all
primary links are down or saturated, then traffic is distributed across all available backup links
until the primary links become available.
Private links — used only for traffic that matches IP/Application routing rules or if specified
explicitly in the configuration of a VPN. Private links are not used at all for default outbound or
inbound link balancing. They are used only if explicitly referenced.