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Barracuda Link Balancer

How does bandwidth management work with my Barracuda Link Balancer on firmware version 2.1 and above?

  • Type: Knowledgebase
  • Date changed: 2 years ago

Solution #00004866



Applies to Barracuda Link Balancers, firmware version 2.1 and above.



You can configure your bandwidth management from the admin GUI of your Barracuda Link Balancer in Policy > Bandwidth Mgmt. Here you will find two sections: Quality of Service and Quality of Service Rules.


Quality of Service
Use this section to create or edit bandwidth rules that specify the priority that the Barracuda Link Balancer gives to outbound traffic. Bandwidth rules are executed after it has been determined which WAN link the traffic will use. These rules apply to all traffic, including VPN traffic, regardless of whether the Barracuda Link Balancer firewall is enabled or not.

If the amount of traffic on the network is more than what can be sent, traffic from high priority applications is allocated a greater share of the bandwidth. You may want to create a rule that reduces the priority of ftp traffic so that uploading and downloading of files does not impact other applications. You may also want to create a rule to increase the priority of SIP traffic so that calls will not be dropped.

Each rule describes a set of traffic based on one or more parameters: source IP address or range, destination IP address or range, application or applications, time, day of the week, and WAN link. If the conditions are met, the rule assigns a bandwidth priority and contention priority.

The priority and contention levels are compliant with the DiffServ specification. The Barracuda Link Balancer inserts DiffServ bits if the traffic matches the Quality of Service rules on this page. It applies bandwidth priority and contention levels based on those bits, even if they are set by another device. Traffic that does not have any Diffserv bits set will be assigned the Default class.

To create or change a Quality of Service rule:


  1. Complete the following fields:
    • Rule Name - Required field. May include spaces.
    • Source IP Address/Range - Leave blank to match all or specify the IP address of the originating system or network. Alternatively, enter an IP address range (e.g. where the two IP addresses that define the range are separated by a hyphen "-"
    • Source Netmask - Leave blank or enter a netmask (e.g.
    • Destination IP Address/Range - Leave blank to match all or specify the IP address of the destination system or network. Alternatively, enter an IP address range (e.g. where the two IP addresses that define the range are separated by a hyphen "-".
    • Destination Netmask - Leave blank or enter a netmask (e.g.
    • Services - Select * for any protocol or port combination or select an application from the list. Click the plus sign.
    • Start Time and End Time - Leave blank or enter the start and end time in hh:mm format.
    • Days - Select the day check box or boxes.
    • Link - Select whether this rule applies if this traffic is going to use any link or only one. If a specific link is selected, the Min. and Max. Bandwidth boxes will show the values for the Bandwidth Priority level.
    • Bandwidth Priority - Select the level to be used. The values for the level and the display unit shown in the Min. and Max. Bandwidth boxes are configured on the Policy > Configuration page.
    • Contention Priority - Select the priority for this traffic within the bandwidth priority level if some traffic must be delayed. Per the DiffServ specification, if the bandwidth priority level is 1, no contention priority value is allowed.
  2. Click Add New Rule to create a new rule or click Save Changes if you are editing a rule.

Quality of Service Rules
Once the rules have been created the table under Quality of Service Rules shows those rules. The rules are arranged in the table from top to bottom in order of precedence. Only the first rule that matches the profile of the traffic is executed. Change the order of the execution of the rules that you have created by selecting a row and clicking the up or down button.

To edit a rule, click the edit icon in that row. The values for the rule will appear in the Quality of Service section. Update the values and click Save Changes.

To delete a firewall rule, click the trash can icon in that row.


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