Tell me more ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.
up vote 0 down vote favorite

I have always noticed an IP something "169.254.x.x" attached even when I am not connected to any network in my Windows operating system.

In Linux, when I list my routing table. 

$ ip route show

I get an entry like

169.254.0.0/16 dev eth0  scope link  metric 1000

Can somebody explain me what is this ip actually. Whether its something like the 127.0.0.0/8 family.

Edit: In ec2, each instance can get meta-data regarding their own by making HTTP requests to this IP. 

$ curl -s http://169.254.169.254/user-data/

So can someone tell me to whom this ip is actually assigned ?

share|improve this question

3 Answers

up vote 9 down vote

These are dynamically configured link-local addresses. They are only valid on a single network segment and are not to be routed.

Of particular note, 169.254.169.254 is used in Amazon EC2 and other cloud computing platforms to distribute metadata to cloud instances.

share|improve this answer
So can u tell me that 169.254.169.154 is assigned to whom in ec2. – pradeepchhetri Sep 13 '12 at 10:04
The blue text means a link that you can click on for more information. Please do so. – Michael Hampton Sep 13 '12 at 10:06
But there is nothing mentioned to whom this ip is assigned to ..regarding the internals in terms of virtualization. – pradeepchhetri Sep 13 '12 at 10:13
That address is not a public address, it is in the same scope as 10.x.x.x, 192.168.x.x etc, many people around the world could have this address, it is private. – Alex Berry Sep 13 '12 at 10:14
1  
@pradeepchhetri It's not assigned to anyone. It's a special-use address. – Michael Hampton Sep 13 '12 at 10:18
up vote 4 down vote

In almost all circumstances that's a IP assigned automatically by an interface that's set to get its IP via DHCP but can't get one.

share|improve this answer
up vote 4 down vote

It's a IPv4 link local address, as defined in rfc3927. Usually ZeroConfig/Bonjour/mdns et al enabled boxes are setup to have IPv4 ll address to enable (home) networking without the presence of an DHCP or unicast DNS server.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.