What is the value of ASN in BGP?

What is the range of ASN?

The range of ASN depends on the size of your network and the amount of traffic you have.

ASN are designed to be able to support thousands of hosts. ASN's can only be allocated to hosts in a single Autonomous System (a group of IP addresses).

The maximum range of an ASN is 10,000 hosts. There is no maximum limit on the number of ASN's that can be created. ASN ranges can be configured on the host when the IP address is created. There are some good questions here about using ASN ranges.

What is an AS number in BGP?

The answer: A BGP Route Target

The AS number is commonly known as the prefix number of a route in a BGP routing domain.

The prefix refers to the route's source network prefix and the AS number is commonly associated with an Autonomous System (AS) for each route. There are different ways to explain what an AS is, but I've simplified it for my readers by giving it an acronym: an Autonomous System is simply a group of routers where each router has its own internet address. Think of it as having a group of ISPs together under one management - that group of ISPs will have its own Network Address Space (NAS) which might be 10.0/24. Another example of a NAS is the subnet 172.16.0/12. These are addresses that would usually be given to specific customers on the network.

In Internet Protocol networks, many organisations own multiple IP addresses that they use for their own internal traffic. An organisation's AS might look like this: AS number AS Name 172.0 172.1 ASX Corp 172.2 172.3 ASX Corp 172.4 172.5 ASX Corp

Now, these are all individual ASs. As we talk about the AS numbers, you'll hear terms like "prefix" and "route target." What does that mean?

An AS number is a Route Target in BGP. In IP networking, a "route target" is a way to specify a forwarding path through a network. For example, if I have two network interfaces in my computer - NIC 1 and NIC 2. If I have a static route in my routing table which says "10.0/24 via 10.8.1" - then the route will go through the interface on the 10.0/24 subnet first, and the destination 10.1 will be the gateway for that traffic. This is the common approach - I'll have a direct link between 10.0/24 and the gateway on the 10.0/24 network. If I want to send traffic from 10.0/24 to 10.11.