EtherChannel Issue

Hi,

I am having an issue with a four port ether-channel between a Big IP 2000 and a Cisco 3750. Looking at the interface stats on the F5, outbound traffic from F5 back to the clients is well balanced across the four links. However, the inbound traffic from the switch only uses two of the available four.

Load balancing method on the Cisco is src-IP, and src-dest-IP on the F5. we have tried various permutations of LB method, but still only receiving traffic on the two ports. Could this be due to other settings on the ether-channel setup? And if so, can anybody point me in the right direction please? We are currently only getting 2Gbps up and 2Gbps down. All four gig ports are up and set to full duplex.

Thanks

Nick