Hi,
What protocol of traffic is being sent? I assume it's TCP-based.
I'd first check to make sure the interfaces are set to full duplex, and then take a look at the virtual server type and TCP profile options.
You can view/set the interface settings in the GUI under Network >> Interfaces or from the CLI using 'b interface'. Run 'b interface help' for examples.
If you don't need to inspect layer 7, you could change from a standard TCP virtual server to a Performance (L4) VIP with a FastL4 profile. This uses the ASIC for processing the packets and should provide better performance compared with a standard TCP VIP.
You can also tune the TCP profile options for the environment you're testing in. In 9.4.x, F5 added new stock TCP profiles for LAN and WAN environments. You can manually configure these in pre-9.4 versions.
Here are some related AskF5 solutions:
SOL7612: Configuring the media speed and duplex settings for network interfaces
https://support.f5.com/kb/en-us/solutions/public/7000/600/sol7612.html
SOL5017: Overview of virtual server types
https://support.f5.com/kb/en-us/solutions/public/5000/000/sol5017.html
SOL8082: Overview of TCP connection set-up for BIG-IP LTM virtual server types
https://support.f5.com/kb/en-us/solutions/public/8000/000/sol8082.html
SOL7559: Overview of the TCP profile
https://support.f5.com/kb/en-us/solutions/public/7000/500/sol7559.html?sr=1
Advanced design/configuration codeshare LAN/WAN optimized profiles
http://devcentral.f5.com/wiki/default.aspx/AdvDesignConfig.CodeShare
SOL4812: Reasons why interactive traffic, such as Telnet and SSH, is slower when passed through BIG-IP
https://support.f5.com/kb/en-us/solutions/public/4000/800/sol4812.html
SOL7399: Configuring a LAN-optimized TCP profile
https://support.f5.com/kb/en-us/solutions/public/7000/300/sol7399.html
SOL7402: Configuring a WAN-optimized TCP profile
https://support.f5.com/kb/en-us/solutions/public/7000/400/sol7402.html
How's that for a reading list? :)
I'm sure others here have suggestions as well for making improving the performance through the BIG-IP.
Aaron