How to set secondary dns in a managed network?

Is there a way to set a second dns in a managed network? Would this be done through the ipsec rancher yml in the defaultNetwork? Are there also other ways to set this?

defaultNetwork:
defaultPolicyAction: allow
description: null
dns:
- 169.254.169.250
dnsSearch:
- rancher.internal
hostPorts: true
kind: null
name: ipsec
subnets:
- cidrSize: 24
networkAddress: 10.42.0.0/16

302 External DNS Lookups Fail