Building a robust out of band management network is a critical part of any service provider or large enterprise backbone. Although failures may not occur frequently but believe me if you are not prepared when they happen you will know how OoB management is important and critical.
Network failures do happen for reasons ranging from human errors to power or hardware failures. One of your main objectives as a network designer is to keep your network available and achieve the highest possible up-time. There are a lot of things you can do to achieve these objectives in terms of redundancy and design best practices.
Out of band management network should be in your priorities; specially when it is your last resort in case of big failures that need to be handled as fast as possible.
What is an out of band management network?
Out of band means having a separate dedicated channel or network that you use to reach your network equipment that is different from the path of normal data flows.
The management network must be operational when your network or one of your devices fail. This means the OoB network needs dedicated communication channels, dedicated devices, dedicated power and should not be affected by any kind of failure in any part of your network.
The trade here is between how critical failures are in your network and the cost of building and maintaining an out of band management network. Considering all your requirements for OoB network there are a lot of options to choose from, ranging from simple designs to very complex ones (dial-up, dedicated routers, GSM, etc.) . One of the options I want to highlight in this post is using dial-up access console servers.
what is a dial-up access console server ?
Almost all network equipment available today provide some sort of serial console access that can be used when normal IP communication is not available to reach the box. Some devices also provide a dedicated Ethernet port for OoB management of the device (Topic or another post).
Console servers provide a simple and reliable access to multiple devices collocated in the same site from a single box. The console server connects multiple serial console ports and provide a centralized access to the connected devices. The console server itself can be accessed using secure and dedicated IP communication, dial-up or GSM connectivity.
Using dial-up or GSM provides backup by using a third party network (PSTN or mobile carrier) which is one of our design goals for an OoB management network. Another important consideration is security features of the console servers as you will not be happy if some attacker gained unauthorized access to your network via this backdoor.
Below is a typical out of band management network topology:
If you have not done it yet, go and review your OoB management network design and make sure it will serve you when needed.