I have a Cisco 2621XM router setup running IOS 12.4(21a), which provides internet connectivity via an ADSL line. The router also has several site to site VPN's and GRE/IPSec tunnels. Connectivity to the sites via the GRE/IPSEC tunnels work without a problem as does internet connectivity.
The site to site IPsec tunnels (non-GRE) to other client sites currently display th following: the VPN tunnels come up and pass traffic, however, there seems to be pqacket loss. If I open a ping to a remote host I get reply, request timed out, reply etc. Also, RDP failes to work altogether and SSH is extremely slow.
A constant ping to http://www.google.com or to a host over the GRE/IPsec tunnel is constant and works fine. I have tried a different router in it's place and get the same issue.
Thanks for the reply. Strangely the VPN tunnels that terminate off the Tunnel interfaces don't have a problem, it's just the non-GRE IPSEC tunnels. I've tried adjusting the mtu sizes on the physical outside interface using the above commands, however, I still have the same problem.
I've also tried using the 'mtu 1400' command on the physical interface, however I get:
% Interface FastEthernet0/0 does not support user settable mtu.
Just an update on this, as a test I've setup an additional IPsec tunnel to an ASA5505 (my home ASA). Connectivity over this VPN works without any problems.
I find it quite strange that 3 customer VPN's should display the same problems (dropped packets), yet an IPSec VPN to my home firewall works without any problems. Is there anything I can get the customer to do at their end? Is the problem that their MTU values are considerably lower than my outside interface's MTU?
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We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...