[Gllug] Routing table - help

[- Tethys]

On 5/17/06, TM <tm at tm.uklinux.net> wrote:

> Could anyone help me understand the output of '/sbin/route' (below) please?
>
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
> 192.168.0.0     *               255.255.255.0   U     0      0        0 eth0
> 169.254.0.0     *               255.255.0.0     U     0      0        0 eth0
> default         192.168.0.1     0.0.0.0         UG    0      0        0 eth0

All a routing table just tells you is how a given packet will be sent
in order to reach a particular destination. Thus packets destined for
192.168.0.0/24 will go out on eth0, as will packets destined for
169.254.0.0/16. Everything else will also go out on eth0, but will be
sent to the gateway 192.168.0.1, rather than trying to go directly to
the destination (because the destination won't be on the subnet
connected to eth0).

> I'm very green in the matters of network admin and I don't really understand the
> line with the 169.254.0.0 address(es). Does it mean that someone got into the
> router? Or am I sharing the desktop with some hacker as I type this message?

No, 169.254.0.0/16 is a reserved block for link local addresses (see
rfc3330). You can basically ignore the fact that it's there. The only
time you're likely to see it used is when a rogue Windows server
decides to set itself up as a DHCP server, and start issuing IPs in
that range to all and sundry and generally screwing up your network.

Tet
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