Carp and port trunking

[Max Laier]

On Saturday 11 December 2004 21:02, Mathieu Arnold wrote:
> +-Le 11/12/2004 20:47 +0100, Max Laier a dit :
> | On Saturday 11 December 2004 20:26, Mathieu Arnold wrote:
> |> Hi,
> |>
> |> I've been wondering, would it be possible to use Carp on two routers in
> |> load balancing mode, connected to 2 trunked ports a switch ?
> |
> | Not entirely sure what you mean. Could you try to draw an ascii "art" of
> | what  you have in mind?
>
> Oh, hum, will that get you in what I have in mind
>
>        outside
>
>   +----+          +----+
>   | R1 |--pfsync--| R2 |
>   +----+          +----+
>       \ Carp here  /
>        \          /
>         \        /
>          \      /
>           \    /   trunk on those 2 ports
>    +-------------------+
>    |   switch          |
>    +-------------------+
>
>        customers here
>
>
> In that case, both routers always work, the switch is sending packets to
> one or the other as the ports leading to them are trunked.
>
> Is that clear enough ?

Yes. But I am afraid that this will not work. The CARP loadbalancing works 
based on client MAC address. On receive we calculate a hash and determine if 
we or the other server is responsible and answer accordingly. With trunking 
it might happen that a request is send to the wrong server, which will not 
reply as it thinks the other one is responsible.

Depending on the routing situation "above" your picture it might be possible 
to do it with pfsync alone - i.e. no CARP required, just let the trunking do 
the load balance. Failover is not easily possible with trunking anyhow.

-- 
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