This lab walks you through GCP Cloud Router.
Duration: 45 minutes
Cloud Router can't be used by itself but it is required for Cloud NAT or Interconnect or VPN.
From Fig1: Let's understand the concept with the help of the below architecture. Consider you have a VPC Network on Google Cloud and an On-premise office network that was connected using VPN Gateway. After a few days, a new network is added to the on-premise network with a name server network. Now you have to add static routes to the routing table in Google Cloud manually and also you need to re-configure your VPN. This is still fine but considers a case when a new network is added quite frequently or the network is destroyed. Same you have to do manually.
From Fig2: Now, Cloud Router helps you overcome the above problem by automatically adding dynamic routes. Cloud Router peers with on-premise VPN Gateway or Router. The routers exchange topology information through BGP(Border Gateway Protocol). The Cloud Router advertises subnets from its VPC Network to the on-premise gateway via BGP. By doing this, any topology changes will be propagated automatically between your VPC and on-premise network. The Cloud Router learns on-premise routes through BGP.
From Fig3: Users don't sense disruptions, as you see if a link fails to VM1, Cloud Router can automatically re-route traffic if a path is available.
Creating a GCP Cloud Router.