ifconfig up inserts unwanted route

When I do

ifconfig eth1 10.184.79.103 up

I get the following routing table:

Destination Gateway Genmask Flags Metric Ref Use Iface
10.184.79.0 * 255.255.255.224 U 0 0 0 eth1
10.184.79.96 * 255.255.255.224 U 0 0 0 eth1
192.168.20.0 * 255.255.255.0 U 0 0 0 eth0
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
default 192.168.20.252 0.0.0.0 UG 0 0 0 eth0

Where is the 10.184.79.96 coming from?

I've grepped everything in /etc /etc/sysconfig /etc/sysconf/network-scripts
/etc/rc.d and can find no reference to 10.184.79.96.

This does not happen if I give the interface another IP address
(e.g. 10.184.79.104). Any ideas?

-------------------------------
[root@baz /root]# uname -a
Linux baz 2.4.2-2 #1 Sun Apr 8 20:41:30 EDT 2001 i686 unknown
--------------------------------

Baz

> Where is the 10.184.79.96 coming from?
>

This is the network address for 10.184.79.103 with netmask 255.255.255.224.
Here's a breakdown of the IP networks starting with 10.184.79. using that
netmask:

Network Address Host range
Broadcast
0 1-30
31
32 33-62
63
64 65-94
95
96* 97-126*
127*
128 129-158
159
160 161-190
191
192 193-222
223
224 225-254
255


The mystery is actually why you have a local route to 10.184.79.0 when you
are not on that network.


> This does not happen if I give the interface another IP address
> (e.g. 10.184.79.104). Any ideas?

None. That address is in the same network based on a 255.255.255.224 netmask
and should generate the same route. If you use an address with the last byte
falling in the range of 1-30, then the 10.184.79.0 route would make sense
and not the 10.184.79.96 route. Whether you use 103 or 104 should not make
any difference.


--

wcardwell at nc dot rr dot com

In article <dUu1b.11034$(E-Mail Removed) >,
W Cardwell wrote:
>> This does not happen if I give the interface another IP address
>> (e.g. 10.184.79.104). Any ideas?
>
> None. That address is in the same network based on a 255.255.255.224 netmask
> and should generate the same route. If you use an address with the last byte
> falling in the range of 1-30, then the 10.184.79.0 route would make sense
> and not the 10.184.79.96 route. Whether you use 103 or 104 should not make
> any difference.

My guess is that we're not seeing the whole picture. ifconfig will by
default use the approriate netmask and broadcast for the Class (A,B,C)
of the IP address. 10.x.y.z is Class A: broadcast 10.255.255.255,
netmask 255.0.0.0 (8 bits).

If you assign 10.184.79.103 to an interface with no other ifconfig
parameters given, you'll get the default ... unless it had been
previously given the 255.255.255.224 (27-bit) netmask. In that case the
former netmask value would be remembered and used.

Please see my earlier post in the PPP script thread: when an interface
is taken down (ifconfig $IF down) the IP address and other settings are
saved and will be displayed in "ifconfig -a" or "ifconfig $IF" output.
--
/dev/rob0 - preferred_email=i$((28*28+28))@softhome.net
or put "not-spam" or "/dev/rob0" in Subject header to reply