Resolved, sort of: [PLUG] Network is unreachable

Don Buchholz buchholz at easystreet.com
Tue Dec 28 20:20:55 UTC 2004


techmage at aracnet.com wrote:

> Richard C. Steffens wrote:
>
>> Kernel IP routing table
>> Destination     Gateway         Genmask         Flags Metric Ref    
>> Use Iface
>> 192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        
>> 0 eth0
>> 169.254.0.0     0.0.0.0         255.255.0.0     U     0      0        
>> 0 eth0
>> 127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        
>> 0 lo
>> 0.0.0.0         192.168.0.1     0.0.0.0         UG    0      0        
>> 0 eth0
>>
>> I understand the 192.168 and the 127 IP addresses, above, but I don't 
>> recognize
>
>> 169.245.0.0. Is that likely to be Comcast, my ISP?
>>
> I had this same question last week when running down a Fedora core issue.
> The 169 is a built in place holder(yeah, don't ask me why))
> even flushing the tables doesn't remove it.
> Or at least this was the explanation from my Boss when I asked. 

The 169.254.0.0/16 network has been allocated by the IANA for link-local
usage for a number of years now.  The idea being to allow systems to connect
to an IP network with "zero-configuration".

    http://www.zeroconf.org/

On RedHat (FC-2, FC-3, and I think RHEL-3) systems, you can disable the
169.254/16 nonsense by putting "NOZEROCONF=yes" in /etc/sysconfig/network.

When TCP/IP was only installed/maintained on large, multi-user systems
the need to manually configure an IP address and network mask (and possibly
a default gateway or run some program to find a route off the local network)
was not considered a problem.  However, as the number of IP devices began
to grow, this started to become a chore.  BOOTP and DHCP were developed
(among other reasons) to give network admins the ability to reconfigure
IP nodes without having to physically visit the machine.

LAN administrators noted (quite correctly) that Novel IPX and the Appletalk
networks didn't need all this per-host maintainence and tweaking.  (Small)
Mac networks were great -- you plug it in, and it worked!  This is the
genesis of the "zero configuration" project in the TCP/IP world. 






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