Cisco Bug: CSCuq17045 - AnyConnect blocking DHCPv6 replies causes loss of IPv6 address
Nov 27, 2020
- Cisco AnyConnect Secure Mobility Client
Known Affected Releases
Symptom: AnyConnect reconnects periodically causing VPN traffic drops. Reconnect might take a couple of seconds or only one second. Windows 7 loses IPv6 address after AnyConnect VPN is connected because DHCPv6 renew / rebind replies are not getting to DHCPv6-Client Windows process. The packets are seen with Wireshark on Windows 7 interface, but DHCPv6-Client doesn't get them. Errors are seen in Windows event log: "DHCPv6-Client, error 1003, Your computer was not able to renew its address from the network". Conditions: Windows 7 having IPv4 and IPv6 address on its interface. IPv6 address assigned using DHCPv6 server, with short renew time. E.g.: Preferred lifetime: 30s Valid lifetime: 60s T1: 15s T2: 45s AnyConnect connecting to the VPN gateway using either IPv4 address or IPV6 address. For IPv6 reconnects are more frequent.
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