I'm pretty sure this is a firewall issue, let me explain the issue I have.
We have 2 ASA 5520's in Active/standby mode. The 'outside' port it connected to a VLAN on a 3750 switch where our 50mb lease line is (ISP Cisco router). The 'inside' of the ASA goes into another VLAN on the 3750 switch where our internal LAN switches are. On this 3750 switch there are various other VLANs that are sub-interfaces on the ASA via the trunk from the 3750 to ASA.
I've been running some speed test for our Internet lease line out of hours. It is a 50mb line and download speeds are around the 47mb mark which is fine.
Now the issue, the upload speeds are only ever 8-11mb and I have tried it on variuos different location on the internal LAN and get the same results.
If I go onto a server in a VLAN on the 3750 switch again I get the same issue, as the servers travel via the trunk to the ASA and out to the 'outside' interface to the VLAN where the Internet router is.
Now if I put a laptop directly into this outside VLAN on the 3750 where our 'outside' interface of the ASA is and ISP router then I get an upload of 47mb! I had to give the laptop a public IP and the gateway of the ISP router.
It just seems anything that has to pass through the firewall it has an slow issue transmitting/uploading data outbound to the Internet.
Our ASA also have the IPS module, I turned this off and it made little difference. To turn the module off (only way I know) is to use Cisco IPS Manager Express > confgiuration > Event Action Rules > Rules0 > disable event action. Also on the ASA usign the ASDM I went to Service Policy Rules and unticked the interfaces to monitor.
Can you thing of any other steps I can do? Is it a NAT/PAT issue? I am lost for ideas.