On 12/09/2014 02:42 PM, Zachary McGibbon wrote:
I'm looking for some input on a situation that has been plaguing our new AnyConnect VPN setup. Any input would be valuable, we are at a loss for what the problem is.
We recently upgraded our VPN from our old Cisco 3000 VPN concentrators running PPTP and we are now running a pair of Cisco 5545x ASAs in an HA active/standby pair.
The big issue we are having is that many of our users are complaining of low speed when connected to the VPN. We have done tons of troubleshooting with Cisco TAC and we still haven't found the root of our problem.
Some tests we have done:
- We have tested changing MTU values - We have tried all combinations of encryption methods (SSL, TLS, IPSec, L2TP) with similar results - We have switched our active/standby boxes - We have tested on our spare 5545x box - We connected our spare box directly to our ISP with another IP address - We have whitelisted our VPN IP on our shaper (Cisco SCE8000) and our IPS (HP Tipping Point) - We have bypassed our Shaper and our IPS - We made sure that traffic from the routers talking to our ASAs is synchronous, OSPF was configured to load balance but this has been changed by changing the costs on the links to the ASAs - We have verified with our two ISPs that they are not doing any kind of filtering or shaping - We have noticed that in some instances that if a user is on a low speed connection that their VPN speed gets cut by about 1/3. This doesn't seem normal that the VPN would use this much overhead - We do not have the issue when connecting to VPN directly on our own network, only connections from the Internet
If you have any ideas on what we could try net, please let me know!
- Zachary
What OS builds? At one point the code had an 8 packet hard coded window per tcp flow, which capped ssl over tcp window size to about 5mbps depending on RTT. Recent 8 branches raised this to something more reasonable that capped around 20 mbps. DTLS over udp and IPSEC tunnels did not have this issue. -- -James