Assumptions

  • You have completed the Route Registrar stories

What

As you learned in the Route Registrar module, Route Registrar is used to create routes that make CF components available to off-platform users. You could use these routes for talking from one CF component to another, but you should not. Using Route Registrar in place of internal component routes (1) exposes CF components unnecessarily to the big bad internet and (2) adds extra hops through the load balancer and GoRouter, which cause latency.

So what do you do when one component wants to talk to another?

You use Bosh DNS!

In this Bosh DNS story series you are going to add a custom URL for an HTTP server and trace the DNS requests for Bosh DNS routes and non-Bosh DNS routes.

Vocab

DNS - stands for Domain Name System. DNS translates domain names (urls) to IP addresses. You can do a DNS request in the terminal by using the command line tool dig. With dig you can learn that neopets.com resolves to 23.96.35.235.

Bosh DNS - provides native DNS Support for deployments (in our case, Cloud Foundry). It gives the bosh release creator (Rahcel, that’s (probably) you!) an easy way to reference other VMs with load balancing. For example, you could set up Bosh DNS such that cc.cf.internal resolves to the IP for the VM where the Cloud Controller lives. This Bosh DNS server is typically deployed on every Bosh deployed machine in a deployment (that is, every Cloud Foundry VM) using a Bosh addon.

Bosh DNS Routes - routes available via Bosh DNS that route to Cloud Foundry components.

Alias - a custom Bosh DNS Route. For example you can make the alias meow.meow send traffic to the api VM. Fun!

External URLs - non-CF urls. Anything on the internet. Example: neopets.com.

Notes

  • This set of stories uses the instance group my-http-server that was created in the Route Registrar set of stories. It is handy to use this VM with nearly nothing on it so that there is much less traffic on it.
  • The networking program does not maintain Bosh DNS. However, DNS resolution is an important part of the networking traffic flow, so it is important to understand how it works.

Resource