I have 2801 ISR devices on several sites, I faced an issue with this device that tha maximum bandwidth between the sites using IPSec VPN is near 600Kbit/s whereas the Internet line capacity is 5-10 Mbit/s. One node is near San Francisco (5Mbit/s burstable to 100Mbit/s) and the other is Chicago (10Mbit/s), between the nodes 600Kbit/s the maximum speed over the IPSec tunnel (the line utilization doesn't reach the 500Kbit/s when I started the test) the CPU usage of the 2801 device is maximum 18% was during the test. If I donwload something from the Internet (from Microsoft) I can see that the provided service reach 10 and 5 Mbit/s what has been ordered. (IOS is c2801-advsecurityk9-mz.124-13d.bin)
What can be the root cause?