Localhost route missing

[Charles Steinkuehler]

Jon Moss wrote:
> A couple of weeks ago, when I was having trouble with my web server, I
> noticed that I don't have a localhost route:
> 
> ]$ cat hosts
> # Do not remove the following line, or various programs
> # that require network functionality will fail.
> 127.0.0.1       lumcweb         localhost.localdomain   localhost
> 192.168.0.33    lumcweb.localdomain     lumcweb
> 192.168.0.25    MossLinux       MossLinux
> 24.94.162.101   smtpserver
> ]$ netstat -r
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags   MSS Window  irtt
> Iface
> 192.168.0.0     *               255.255.255.0   U         0 0          0 eth1
> 169.254.0.0     *               255.255.0.0     U         0 0          0 eth1
> default         192.168.0.1     0.0.0.0         UG        0 0          0 eth1
> 
> Yet my hosts files includes it.  This server is running Fedora Core 2.
> 
> I can also ping the localhost just fine:
> 
> PING lumcweb (127.0.0.1) 56(84) bytes of data.
> 64 bytes from lumcweb (127.0.0.1): icmp_seq=0 ttl=64 time=0.071 ms
> 64 bytes from lumcweb (127.0.0.1): icmp_seq=1 ttl=64 time=0.063 ms
> 64 bytes from lumcweb (127.0.0.1): icmp_seq=2 ttl=64 time=0.060 ms
> 64 bytes from lumcweb (127.0.0.1): icmp_seq=3 ttl=64 time=0.063 ms
> 
> Should I be concerned?

Probably not...the routes for local are kind of 'hidden'...for example
on my debain box (using the iproute command...your FC box will look
similar..."up2date iproute" (or however that works now) if you don't
have iproute installed):

<quote>

ada:~# ip rule list
0:      from all lookup local
32766:  from all lookup main
32767:  from all lookup default

ada:~# ip route list table local
broadcast 127.255.255.255 dev lo  proto kernel  scope link  src 127.0.0.1
broadcast 65.16.44.223 dev eth0  proto kernel  scope link  src 65.16.44.212
local 65.16.44.212 dev eth0  proto kernel  scope host  src 65.16.44.212
broadcast 65.16.44.208 dev eth0  proto kernel  scope link  src 65.16.44.212
broadcast 127.0.0.0 dev lo  proto kernel  scope link  src 127.0.0.1
local 127.0.0.1 dev lo  proto kernel  scope host  src 127.0.0.1
local 127.0.0.0/8 dev lo  proto kernel  scope host  src 127.0.0.1

ada:~# ip route list table main
65.16.44.208/28 dev eth0  proto kernel  scope link  src 65.16.44.212
default via 65.16.44.209 dev eth0

ada:~# ip route list
65.16.44.208/28 dev eth0  proto kernel  scope link  src 65.16.44.212
default via 65.16.44.209 dev eth0

ada:~# netstat -r
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
65.16.44.208    *               255.255.255.240 U        40 0          0 eth0
default         host44-209.disc 0.0.0.0         UG       40 0          0 eth0

</quote>

Note the local routes are in the local table, but the default table used by
routing tools is 'main'.  For a more detailed description of how this all works,
see the Linux Advanced Routing and Traffic Control HOWTO:

http://lartc.org/

Chapter four introduces you to the routing policy table (ip rule list), and
some of the things you can do with it...

-- 
Charles Steinkuehler
charles at steinkuehler.net