Extra 169.254.0.0 eth0 route entry

**kihbord** · 09-15-2003

I recently installed Redhat 8 on a machine. When I was going thru
the installed setup, I noticed something that I did not find in other
setups I previously did. When I execute the route command,
I get the following output:

Kernel IP routing table
Destination Gateway Genmask Flags Metric ........ Iface
172.16.7.0 * 255.255.255.0 eth0
169.254.0.0 * 255.255.0.0 eth0
127.0.0.0 * 255.0.0.0 lo
default 172.16.7.8 0.0.0.0 eth0

What is the 169.254.0.0 extra route that is displayed?

**Dolda2000** · 09-15-2003

That's a good question. What do you get if you run "ip addr ls"?

**kihbord** · 09-16-2003

Hi Dolda2000,

Here's the output for ip addr ls

1: lo: <LOOPBACK, UP> mtu ....
link/loop ....
inet 127.0.0.1/8 ....
2: eth0: ....
link/ether ....
inet 172.16.9.3/24 brd 172.16.9.255 scope global eth0

I did some search and the 169.254.0.0 seems to be a reserved
address that has something to do with zeroconf dhcp.... any idea?

**Dolda2000** · 09-16-2003

I don't know exactly how that address range is defined, but I think that it's commonly used when no DHCP servers are responding. whois.arin.net refers to RFC 3330, but I haven't read that one.
I find it strange that you have gotten a route to it even though no actual address has been set up to use any address within it. Can you check somehow if it is the DHCP client that sets it up, eg. by shutting down the interface, removing the route (if it's still there) and bring the interface back up. I assume that the interface actually is using DHCP?

**kihbord** · 09-16-2003

That's the strange part. I had the interface setup for static IP. If I do an
ipdown eth0 the route will go away. If I do an ipup eth0 it will come back.

**Dolda2000** · 09-16-2003

What happens if you try to set it up manually, ie. like this:

Code:

ip link set eth0 up
ip addr add 172.16.9.3/24 dev eth0 label eth0

What routes does that yield? Do you have anything strange in your ifcfg-eth0?

**e1guap0** · 09-23-2003

just to support what DOLDA had said. I know in windows 98 2000 and XP if there is no dhcp server available then your computer will automatically assing itself an ip address. Furthermore I believe that its a private ip address for home use.

**scientica** · 09-23-2003

Originally Posted by kihbord

I did some search and the 169.254.0.0 seems to be a reserved
address that has something to do with zeroconf dhcp.... any idea?

This might help, it's the RFC 3330: http://www.rfc-editor.org/rfc/rfc3330.txt
it mentions several address spaces, including 169.254.0.0/16

Code:

IANA                         Informational                      &#91;Page 2&#93;

RFC 3330               Special-Use IPv4 Addresses         September 2002


   169.254.0.0/16 - This is the "link local" block.  It is allocated for
   communication between hosts on a single link.  Hosts obtain these
   addresses by auto-configuration, such as when a DHCP server may not
   be found.

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