network query; route command

[Rick Stevens]

Shelagh Manton wrote:
> Paul Howarth wrote:
> 
> 
>>Shelagh Manton wrote:
>>
>>>Hello,
>>>I've been reading up on networks and comparing what the NAG from TDLP has
>>>to say and what my computer settings look like. Um... I did find a few
>>>differences (problems?). I will be upgrading to ADSL sometime soon and
>>>wanted to be more prepared as my ISP don't know nothing about Linux.
>>>
>>>One thing which worries me is when I ask the route command to add or del
>>>a network or IP address I get this message.
>>>
>>>SIOCADDRT: Invalid argument
>>>
>>>or SIOCDELRT: No such process
>>>
>>>When I ask it for information "route -e" I get back a table which
>>>includes an IP address I did not give it, and is not from My ISP. And of
>>>course I can't delete it using the "route del 163.254.0.0" command
>>
>>Are you sure it's not "169.254.0.0" rather than "163.254.0.0"?
>>
>>What's the output of "netstat -rn" and what are the routes you want to
>>add/remove?
>>
>>Paul.
>>
> 
> Yes, when I look more carefully, that is the very IP address. I wanted to
> follow the instructions of the NAG where it says to add the 127.0.0.1 lo
> address with the route add command. The address it shows at present is
> 127.0.0.0 which is the lo network, and does not have 127.0.0.1 at all. Is
> this a problem? 
> 
> [shelagh at pandorasbox shelagh]$ netstat -rn
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags   MSS Window  irtt
> Iface
> 220.244.163.3   0.0.0.0         255.255.255.255 UH        0 0          0
> ppp0
> 192.168.32.0    192.168.32.3    255.255.255.0   UG        0 0          0
> eth0
> 192.168.32.0    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         220.244.163.3   0.0.0.0         UG        0 0          0
> ppp0
> 
> What I'm eventually hoping to achieve is understanding of NAT so that my 2
> sons machines can access the internet through my internet connected
> computer. But, just one slow step at a time, otherwise my brain might
> explode.

127.0.0.1 is always tied to lo--which isn't a real interface.  It's a
pseudo interface, implemented completely in software, that allows a
machine to talk to itself using network protocols.  The 127.0.0.0/8
network is not routable over the internet and (technically) doesn't
need an entry in a route table since there is no external connection.
A route is present, so ALL network-related stuff appears to work.

169.254.0.0 is a Microsoft-invented thing for APIPA.  This allows a
machine to configure an IP address for itself in lieu of an available 
DHCP server giving it one.  The machine polls the 169.254/16 network to 
find an unused address.  If it finds one, it grabs it and uses it until
a DHCP server becomes available and gives it a dynamic address.
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-    "Hello. My PID is Inigo Montoya.  You `kill -9'-ed my parent    -
-                     process.  Prepare to vi."                      -
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