How to change default source address?

[Julian Elischer]

Jamie Ostrowski wrote:
> On Thu, Jul 23, 2009 at 9:57 AM, Lucian at lastdot.org <lucian at lastdot.org>wrote:
> 
>> Hi guys,
>>
>> I need to change the default source address on a freebsd server.
>> My situation is somehow similar to this
>> (http://marc.info/?l=freebsd-questions&m=122535960804508&w=2).
>> In linux i can easily do it like:
>>
>> ip ro replace default via 10.10.10.1 src a.b.c.d (where a.b.c.d is em0
>> alias).
>>
>> Any ideas?
>>
> 
> 
>   There may technically be a way to do this. If you set your default route
> to the gateway of your secondary network assigned to your card, it will
> actually change the source ip of your packets to be coming from the machine.
> 
> 
>   For example, let's say I've got my nic configured like this:
> 
>    fxp1: 172.16.1.5 netmask 255.255.255.0
>    fxp1_alias0: 192.168.0.2 255.255.255.0
> 
>   If I do:
> 
>    route delete default
>    route add default 192.168.0.1
> 
>   The machine will send all the packets bound for any default address out
> the interface 192.168.0.2 to 192.168.0.1, and it will show up on the other
> end of the connection coming from that address, rather than 172.16.1.5.
> 
>   Of course, that will only work if, in your case, your secondary ip address
> you want to use is on a different subnet than your primary on the machine.
> Since you didn't specify, I'm making that assumption.
> 
>   Depending on your application, your mileage will vary.

you could set up 2 routing tables and assign different apps to use 
different tables.

> 
> 
>     - Jamie
> 
> 
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> 
> 
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