Can lagg0 failback be prevented?

[Barney Cordoba]

--- On Tue, 9/15/09, Peter Steele <psteele at maxiscale.com> wrote:

> From: Peter Steele <psteele at maxiscale.com>
> Subject: Can lagg0 failback be prevented?
> To: "freebsd-net at freebsd.org" <freebsd-net at freebsd.org>
> Date: Tuesday, September 15, 2009, 8:23 PM
> We're using the lag driver to provide
> automatic failover in case of a network outage. The default
> configuration looks like this:
> 
> lagg0:
> flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST>
> metric 0 mtu 1500
>        
> options=19b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4>
>         ether 00:a0:d1:e3:58:26
>         inet 192.168.17.40 netmask
> 0xfffff000 broadcast 192.168.31.255
>         inet 192.168.22.11 netmask
> 0xffffff00 broadcast 192.168.22.255
>         media: Ethernet autoselect
>         status: active
>         laggproto failover
>         laggport: nfe1 flags=0<>
>         laggport: nfe0
> flags=5<MASTER,ACTIVE>
> 
> If nfe0 was to fail, we get an (almost) automatic failover
> to nfe1:
> 
> lagg0:
> flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST>
> metric 0 mtu 1500
>        
> options=19b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4>
>         ether 00:a0:d1:e3:58:26
>         inet 192.168.17.40 netmask
> 0xfffff000 broadcast 192.168.31.255
>         inet 192.168.22.11 netmask
> 0xffffff00 broadcast 192.168.22.255
>         media: Ethernet autoselect
>         status: active
>         laggproto failover
>         laggport: nfe1
> flags=4<ACTIVE>
>         laggport: nfe0
> flags=1<MASTER>
> 
> The problem we're having is when nfe0 comes online again, a
> failback occurs making nfe0 active again. This causes a
> momentary network outage that we want to prevent. Is there a
> way to configure the lagg device to stay with the currently
> active interface, even if the MASTER interface comes back
> online?

Why don't you just load balance? Usually fallback implies that 
one link is preferred (such as a more favorable path, or higher 
speed). 

Barney