Re: 3 nics in linux box (iptables)
From: Moe Trin (ibuprofin_at_painkiller.example.tld)
Date: 04/29/05
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Date: Thu, 28 Apr 2005 18:48:01 -0500
In article <d4ptrc$aqh$1@news-int.gatech.edu>, Jeremy wrote:
>> On Tue, 26 Apr 2005, Jeremy wrote:
>>>I have a Fedora core 3 (2.6.11-1.14_FC3)
>Here's the output of netstat -rn
>--------------------------------
>Kernel IP routing table
>Destination Gateway Genmask Flags MSS W irtt Iface
>192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
>192.168.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth2
>128.61.me.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
>169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth2
>0.0.0.0 128.61.me.1 0.0.0.0 UG 0 0 0 eth0
>
>I'm not sure where the 4th entry (169.254.0.0) is from--that's the only
>wierd looking thing to me.
This is a "feature" that microsoft has been trying to get standardized since
1998. The idea is that when the MCSE has so screwed up the configuration of
the DHCP server that even a windoze box can't get an address, it will reach
up between it's legs and grab an IP address randomly out of the 169.254/16
range and use that. Several Linux distributions have been adding a route
to the network - perhaps to avoid the 'Martian Packet' error messages when
this happens. I've not seen a Linux box actually assign such an address to
any interface.
If you look inside /etc/sysconfig/network-scripts/ifup you'll probably find:
-----8<-------
# Add Zeroconf route.
if [ -z "${NOZEROCONF}" -a "${ISALIAS}" = "no" ]; then
ip route replace 169.254.0.0/16 dev ${REALDEVICE}
fi
-----8<-------
So if you set NOZEROCONF=yes in the /etc/sysconfig/network configuration
file, this "feature" will be disabled.
>Do I need to remove it?
http://www.ietf.org/internet-drafts/draft-ietf-zeroconf-ipv4-linklocal-17.txt
(8 July 2004 which expired 2 Jan 2005) para 1.9 says "should not" have
zero-conf address if the interface ALSO has a routable (meaning anything
other than 169.254.0.0/16) address. However, this is just a routing table
entry, not an address assignment (check this with /sbin/ifconfig). It's up
to you if you want or don't want the routing table entry (I don't), as any
properly configured router should silently discard packets with these
addresses.
Old guy
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