A trunk is a logical group of interfaces on BIG-IP System. Through link aggregation we can use a trunk for traffic distribution over multiple links. We can combine multiple links and can increase the bandwidth of trunk which will include the addition of bandwidth of individual links.

Below Figure shows the trunk configuration between two devices and two member links on each device:-

Benefits of Trunk :-

Ø  Increase of bandwidth through link aggregation

Ø  Link failover if any of the member links is not available.

Creating a trunk in BIG-IP System:-

 We will follow below steps to create a trunk in BIG-IP system:-

1.     From the BIG-IP configuration utility, Go to Network > Trunks. 

2.     Click Create.

3.     Give the name of the trunk.

4.     We can only Select the interfaces from “Available” field to become part of the trunk and only those interfaces are available which are untagged and do not belong to any other trunk.

5.     Choose the option for Link Selection Policy. The media speed and Duplex mode of member links must be same  on both Peer systems between which we want to establish link aggregation. In the situations where the media properties of the links are not matching, the BIG-IP system has to find the eligibility for the links which can be aggregated. BIG-IP finds out the eligibility of the links for link aggregation on the basis of link selection Policy. Below are the options under this:-

Ø  Automatic Link Selection

With this option, the BIG-IP system will use the lowest-numbered interface of the trunk as a reference link, the system will them aggregate those links which have same media properties and which are connected to the same peer at which reference link is connected. Lets take an example, suppose we have interfaces 1.1 and 1.2 with media speed of 100 Mbps and interface 1.3 has a different media speed of 1 Gbps. BIG-ip system will use interface 1.1 (lowest numbered) as a reference link and it will aggregate interface 1.2 with similar media speed of 100 Mbps with reference link. Interface 1.3 will not form part of link aggregation due to different media speed.

Ø  Maximum Bandwidth Link Selection