Removing an alias can remove routes ?

[Rodney W. Grimes]

> All
>  I ran into a peculiar over the weekend on two FreeBSD 10-STABLE
> servers that has me at a loss. Both servers have the same setup  lacp
> lagg wtih vlans using the lagg as a parent dev.
> On the vlans I have some alias along with the primary ip.  When a
> alias was added or deleted routes that sourced out of the primary ip
> on that vlan were dropped from the routing table.
> 
> 
> So for example. I have lagg0.vlan1044 . (both servers are similarly
> configured as routers / firewalls )
> 
>   [root at pineapple01 ~]# ifconfig lagg0.vlan1044
>   lagg0.vlan1044: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST>
> metric 0 mtu 1500
>           options=300<TSO4,TSO6>
>           ether 00:0f:53:20:9b:d0
>           inet6 fe80::20f:53ff:fe20:9bd0%lagg0.vlan1044 prefixlen 64
> scopeid 0x80
>           inet 10.24.213.84 netmask 0xffffffe0 broadcast 10.24.213.95
>           inet 10.24.212.129 netmask 0xffffffff broadcast 10.24.212.129
>           inet 10.24.213.163 netmask 0xfffffff0 broadcast 10.24.213.175
>           inet 10.24.213.76 netmask 0xffffffe0 broadcast 10.24.213.95
>           inet 10.24.213.94 netmask 0xffffffe0 broadcast 10.24.213.95
>           inet 10.24.213.89 netmask 0xffffffe0 broadcast 10.24.213.95
>           inet 10.24.213.75 netmask 0xffffffe0 broadcast 10.24.213.95
>           nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
>           media: Ethernet autoselect
>           status: active
>           vlan: 1044 parent interface: lagg0
> 
> [root at pineapple01 ~]# netstat -nr4Wl
> ...
>   192.168.144.32/27   10.24.213.65     UGS           0   1500 lagg0.vlan1044
>   192.168.144.96/27   10.24.213.65     UGS           0   1500 lagg0.vlan1044
>   192.168.23.0/24     10.24.213.65     UGS           0   1500 lagg0.vlan1044
>   192.168.120.0/21   10.24.213.65     UGS           0   1500 lagg0.vlan1044
> 
> 
> So I wanted to remove the alias ended in 163 and fix its netmask back to /32
> 
> I ran this
> 
> ifconfig lagg0.vlan1044 inet 10.24.213.163/24 -alias && ifconfig
                                                      ^ delete?

> lagg0.vlan1044 inet 10.24.213.163/32 -alias
> 
> and shortly there after all of the routes that went out lagg0.vlan1044
> were gone . I quickly undid my change and put the routes back but I am
> not sure what caused this ? Anyone have any ideas  I have done this in
> the past with out issue and I am unsure whats changed other then the
> box have a long up time of 463 days .

I believe what happened here is that 10.24.213.163/24 when reduced
to a network address is 10.24.213.0/24, which probably got sent to
the route removal code, which since the route to that covers the
gateway at 10.24.213.65 that gateway was no longer accessable
so all routes via it got removed.

-- 
Rod Grimes                                                 rgrimes at freebsd.org