Re: Ipv6 and preferred_lft

On Mon, Jun 17, 2013 at 12:11:12PM +0000, Martinsson Patrik wrote:
> Hello,
> 
> I'm really trying to understand how keepalived handles ipv6 VIP's and what's the general idea and best practise is, however I seem to miss something.
> I don't understand why you wouldn't want to have keepalived to set the preferred_lft to zero when bringing up the VIP's, or actually what I don't understand is how to make various checks work with the source-address beeing the VIP and not the "iron-address".
> 
> So, here's the simple configuration,
> 
> # keepalived.conf,
> global_defs {
>    notification_email_from [email protected]
>    smtp_server bar.com
>    smtp_connect_timeout 30
>    lvs_id ER-TST-LD-MASTER
> }
> 
> vrrp_instance VI_1 {
>         state MASTER
>         interface eth0
>         lvs_sync_daemon_interface eth0
>         virtual_router_id 56
>         priority 150
>         advert_int 1
>         smtp_alert
>         authentication {
>                 auth_type PASS
>                 auth_pass example
>         }
>         virtual_ipaddress {
>            XXXX:XXX:XXX:XXXX::46
>         }
> }
> 
> virtual_server XXXX:XXX:XXX:XXXX::46  0 {
>     delay_loop 10
>     lb_algo rr
>     lb_kind DR
>     persistence_timeout 900
>     protocol TCP
>     real_server XXXX:XXX:XXX:XXXX::17 0 {
>         weight 1
>         inhibit_on_failure
>         MISC_CHECK {
>           misc_path "/etc/keepalived/check_tcp -H XXXX:XXX:XXX:XXXX::17 -p 21"
>           misc_timeout 30
>         }
>     }
> }
> # end keepalived.conf

What does /etc/keepalived/check_tcp do and where does it expect to get
a response? Does this same problem occur if you use one of the
built-in health checkers?

> So, this would mean that when keepalived performs the check to see if the realserver (XX:17 on port 21) is alive, the source-address of that packet is the VIP (XX:46), which of course also is up on the realserver, which in turns would mean that the packet never returns to keepalived. And thus making keepalived to mark the realserver as down (since it doesnt get any reply).
> 
> So, what I'm I missing here, how is this suppose to work ?
> 
> I've been trying to read the following discussions, they seem to have the same problem,
> http://www.ietf.org/mail-archive/web/v6ops/current/msg15266.html
> http://marc.info/?l=keepalived-devel&m=130200733315039 (there's a patch that would make sense to me, but never got accepted if I'm not mistaken)

I am interested in hearing other opinions on this patch. I have used
keepalived with IPv6 and not noticed this problem. Note that I was
using static IPv6 addresses and I'm under the impression that could
play a role in priority for src address. Thoughts?

Ryan


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