LARTC - May 2002 - ip route src

in LARTC at 4.2.1 Split access

we have: ip route add $net dev $if src $ip

i didn''t understand what does the "src", if someone can
explaint to me.

thanks

C

On Wed, 29 May 2002, Ciprian Niculescu wrote:
> in LARTC at 4.2.1 Split access
>
> we have: ip route add $net dev $if src $ip
>
> i didn''t understand what does the "src", if someone can
explaint to me.
The ''src'' specifies which source address to choose in case a
packet matching
that routing rule does not have a source address yet. This may not seem
useful, until you realise that all outgoing packets generated on the local
machine don''t have a source address when routing...

Doei, Arthur.

-- 
  /\    / |      arthurvl@sci.kun.nl      | Work like you don''t need
the money
 /__\  /  | A friend is someone with whom | Love like you have never been hurt
/    \/__ | you can dare to be yourself   | Dance like there''s nobody
watching

On Wed, May 29, 2002 at 08:54:43PM +0200, Arthur van Leeuwen
wrote:
> The ''src'' specifies which source address to choose in
case a packet matching
> that routing rule does not have a source address yet. This may not seem
Are you sure it is that general?
If I am correct, it only applies to local unbound
traffic.
> useful, until you realise that all outgoing packets generated on the local
> machine don''t have a source address when routing...
That is also to general.
If you generate outgoing traffic, you have the option to bind the
source to an IP address, instead of "give me something default".

So: the src option changes the default source ip address of
outbound traffic going to the specified route.

If you have a multi homed system (meaning more than one ip
address for the same system), you can do a:
wget -SHO /dev/null http://www.telegraaf.nl/
and linux will choose an apropriate source address.

But if you have certain arrangements with somebody that delivers
content only to specific ip addressess, you can tell wget to use
a specific ip address:
wget --bind-address={a local ip address} -SHO /dev/null http://www.telegraaf.nl/
which will overrule the default address.

If you want to know what the default address will be for a
certain destination you can do this:
ip route get {destination}
-- 
begin  ILOVEYOU.VBS 666
<ard@telegraafnet.nl> Telegraaf Elektronische Media
Real geeks don''t get viruses
end