how to enable to use FIPS compliant algorithms in router

[MrBeginner]

I am beginner of FIPS compliant.

I would like to use FIPS compliant algorithams for encryption and authentication.

To use FIPS algorithams ,do we need to change devices to FIPS mode or do we need to enable FIPS feature  ?

let me know 

if we change mode or enable FIPS , it will impact to operation ?

will it impact on current VPN using certificate ? do we need to recreate certificate for vpn setup ?

will it impact current configuration ?

[marce1000]

 - Not all devices will support FIPS mode , what is the router model ?

 M.