Information
By default, perfect forward secrecy (PFS) is enabled on IPsec tunnels, to ensure that past sessions are not affected if future keys are compromised. PFS forces a new Diffie-Hellman key exchange, by default using the 4096-bit Diffie-Hellman prime module group.
See https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/security/vedge-20-x/security-book/config-sec-param.html for more information.
Solution
You can change the PFS setting:
vEdge(config-interface-ipsecnumber)# ipsec
vEdge(config-ipsec)# perfect-forward-secrecy pfs-setting
pfs-setting can be one of the following:
- group-2-Use the 1024-bit Diffie-Hellman prime modulus group.
- group-14-Use the 2048-bit Diffie-Hellman prime modulus group.
- group-15-Use the 3072-bit Diffie-Hellman prime modulus group.
- group-16-Use the 4096-bit Diffie-Hellman prime modulus group. This is the default.
- none-Disable PFS.