Router configuration guidance for specific manufacturers may be found in the IP Transport section of the IPv6 Knowledge Base. For commercial products, the manufacturer’s web site provides guidance.
In 2022, the National Security Agency (NSA) published Network Infrastructure Security Guidance providing comprehensive general guidance for several aspects of network security, including router configuration. In 2020, the NSA also published guidance for Hardening Network Devices to reduce the risk of unauthorized access into a network’s infrastructure.
The next two publications are earlier general references on things to do (and to avoid) when configuring routers. While dated, they are still useful references. The NSA Systems and Network Attack Center (SNAC) published a supplement to an earlier NSA Router Security Configuration Guide offering security principles and guidance for configuration of IPv6 routers, with detailed instructions for Cisco Systems routers.
Other NSA Security Configuration Guides are available here (hover over the word "LIBRARY" in the row of keywords at the top of the screen to see other subject areas). Older NSA Security Configuration Guides are archived here.