Vrrp/CARP/ucarp Problems

[Andrea Venturoli]

Jordan Gordeev wrote:
> The only load balancing that CARP supports, to my knowledge, is ARP 
> level load balancing. From carp(4):
> The ARP load balancing has some limitations.  First, ARP balancing only
>     works on the local network segment.  It cannot balance traffic that
>     crosses a router, because the router itself will always be balanced to
>     the same virtual host.

Forgive me for stepping in, but I had read the above statement over and 
over trying to figure what it meant; perhaps it's not so clear...

If I understood it correctly it's not saying you should not use CARP on 
routers. Instead it's meaning that load-balancing won't cross a third 
router which is on cascade of the two CARP routers.
An image might help to clarify:

+------+ +------+ +------+ .... +------+
|host I| |host J| |host K| .... |host Z|
+------+ +------+ +------+ .... +------+
    |        |        |              |
    \--------+--------+-------------+---------\
                                              |
+------+ +------+ +------+ .... +------+ +--------+
|host A| |host B| |host C| .... |host H| |Router 3|
+------+ +------+ +------+ .... +------+ +--------+
    |        |        |             |         |
    \--------+-----+--+-------+-----+---------/
                   |          |
              +--------+ +--------+
              |Router 1| |Router 2|
              +--------+ +--------+


Suppose you are arp-balancing with CARP on Router 1 & 2, hosts A-H will 
get balanced, but hosts I-Z will all go to the same router (wether 
Router 1 or Router 2). This is because all their incoming packets will 
bear Router 3's MAC address.


Is this interpretation correct?


  bye & Thanks
	av.