Failback causes lost lease

Sean McMurray sean at mvtel.com
Thu Jun 25 21:22:32 UTC 2015


On 06/25/2015 01:39 PM, Gregory Sloop wrote:
> Re: Failback causes lost lease
>
> 	Gregory,
>
> Thanks for your reply.
>
> On 06/25/2015 12:47 PM, Gregory Sloop wrote:
> Re: Failback causes lost lease *SM> In testing my dhcp failover, I 
> pulled the ethernet cable on the primary
> SM> server.
>
> SM> The secondary server acknowleged renewal requests as expected.
>
> SM> Then I plugged the cable back in. After both the primary and secondary
> SM> had moved from communications-interrupted to normal, the secondary 
> logs
> SM> multiple dhcp requests from a client whose lease is owned by the 
> primary
> SM> server. The primary server does not log any of these but the last
> SM> request, reporting that "lease in transition state expired".
>
> SM> Then the secondary server logs a DHCPDISCOVER from that client and
> SM> records it load balancing to the primary server.
>
> SM> The primary server also sees the DHCPDISCOVER and offers a new lease
> SM> that is not the same number as the previous lease. This despite 
> the old
> SM> number not having been reassigned.
>
> SM> The end result is that failback causes my clients to change their ip
> SM> address.
>
> SM> Why does this happen and how can I prevent it?
>
> SM> _______________________________________________
> SM> dhcp-users mailing list
> *SM> dhcp-users at lists.isc.org <mailto:dhcp-users at lists.isc.org>
> SM> https://lists.isc.org/mailman/listinfo/dhcp-users 
> <https://lists.isc.org/mailman/listinfo/dhcp-users>
>
> 1) Logs would be good.
>
Primary Server:
=========

Jun 25 11:33:00 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:33:00 dhcpd: DHCPACK on 10.112.1.1 to 00:19:d1:4d:03:f8 via 
em2.112
Jun 25 11:36:23 dhcpd: timeout waiting for failover peer partner
Jun 25 11:36:23 dhcpd: peer partner: disconnected
Jun 25 11:36:23 dhcpd: failover peer partner: I move from normal to 
communications-interrupted
Jun 25 11:42:38 dhcpd: failover peer partner: peer moves from normal to 
communications-interrupted
Jun 25 11:42:38 dhcpd: failover peer partner: I move from 
communications-interrupted to normal
Jun 25 11:42:38 dhcpd: balancing pool 7f4c9a14cb80 10.112.0.0/13 total 
1024  free 511  backup 512  lts 0  max-own (+/-)102
Jun 25 11:42:38 dhcpd: balanced pool 7f4c9a14cb80 10.112.0.0/13 total 
1024  free 511  backup 512  lts 0  max-misbal 153
Jun 25 11:42:38 dhcpd: balancing pool 7f4c9a143260 10.104.0.0/13 total 
1024  free 512  backup 512  lts 0  max-own (+/-)102
Jun 25 11:42:38 dhcpd: balanced pool 7f4c9a143260 10.104.0.0/13 total 
1024  free 512  backup 512  lts 0  max-misbal 154
Jun 25 11:42:38 dhcpd: balancing pool 7f4c9a13a930 10.96.0.0/13 total 
1024  free 512  backup 512  lts 0  max-own (+/-)102
Jun 25 11:42:38 dhcpd: balanced pool 7f4c9a13a930 10.96.0.0/13 total 
1024  free 512  backup 512  lts 0  max-misbal 154
Jun 25 11:42:38 dhcpd: failover peer partner: peer moves from 
communications-interrupted to normal
Jun 25 11:43:38 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112: lease in transition state expired
Jun 25 11:43:39 dhcpd: DHCPDISCOVER from 00:19:d1:4d:03:f8 via em2.112
Jun 25 11:43:40 dhcpd: DHCPOFFER on 10.112.2.201 to 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:43:40 dhcpd: uid lease 10.112.1.1 for client 00:19:d1:4d:03:f8 
is duplicate on 10.112.0.0/13
Jun 25 11:43:40 dhcpd: DHCPREQUEST for 10.112.2.201 (10.112.0.104) from 
00:19:d1:4d:03:f8 via em2.112
Jun 25 11:43:40 dhcpd: DHCPACK on 10.112.2.201 to 00:19:d1:4d:03:f8 via 
em2.112

Secondary Server:
===========
Jun 25 11:36:21 dhcpd: timeout waiting for failover peer partner
Jun 25 11:36:21 dhcpd: peer partner: disconnected
Jun 25 11:36:21 dhcpd: failover peer partner: I move from normal to 
communications-interrupted
Jun 25 11:37:34 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:37:34 dhcpd: DHCPACK on 10.112.1.1 to 00:19:d1:4d:03:f8 via 
em2.112
Jun 25 11:39:10 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:39:10 dhcpd: DHCPACK on 10.112.1.1 to 00:19:d1:4d:03:f8 via 
em2.112
Jun 25 11:40:11 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:40:11 dhcpd: DHCPACK on 10.112.1.1 to 00:19:d1:4d:03:f8 via 
em2.112
Jun 25 11:40:44 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:40:44 dhcpd: DHCPACK on 10.112.1.1 to 00:19:d1:4d:03:f8 via 
em2.112
Jun 25 11:41:16 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:41:16 dhcpd: DHCPACK on 10.112.1.1 to 00:19:d1:4d:03:f8 via 
em2.112
Jun 25 11:41:47 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:41:47 dhcpd: DHCPACK on 10.112.1.1 to 00:19:d1:4d:03:f8 via 
em2.112
Jun 25 11:42:12 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:42:12 dhcpd: DHCPACK on 10.112.1.1 to 00:19:d1:4d:03:f8 via 
em2.112
Jun 25 11:42:37 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112
Jun 25 11:42:37 dhcpd: DHCPACK on 10.112.1.1 to 00:19:d1:4d:03:f8 via 
em2.112
Jun 25 11:42:38 dhcpd: failover peer partner: peer moves from normal to 
communications-interrupted
Jun 25 11:42:38 dhcpd: failover peer partner: I move from 
communications-interrupted to normal
Jun 25 11:42:38 dhcpd: balancing pool 7f325dbfdb30 10.112.0.0/13 total 
1024  free 511  backup 512  lts 0  max-own (+/-)102
Jun 25 11:42:38 dhcpd: balanced pool 7f325dbfdb30 10.112.0.0/13 total 
1024  free 511  backup 512  lts 0  max-misbal 153
Jun 25 11:42:38 dhcpd: balancing pool 7f325dbf4210 10.104.0.0/13 total 
1024  free 512  backup 512  lts 0  max-own (+/-)102
Jun 25 11:42:38 dhcpd: balanced pool 7f325dbf4210 10.104.0.0/13 total 
1024  free 512  backup 512  lts 0  max-misbal 154
Jun 25 11:42:38 dhcpd: balancing pool 7f325dbeb8e0 10.96.0.0/13 total 
1024  free 512  backup 512  lts 0  max-own (+/-)102
Jun 25 11:42:38 dhcpd: balanced pool 7f325dbeb8e0 10.96.0.0/13 total 
1024  free 512  backup 512  lts 0  max-misbal 154
Jun 25 11:42:38 dhcpd: failover peer partner: peer moves from 
communications-interrupted to normal
Jun 25 11:43:06 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112: lease owned by peer
Jun 25 11:43:13 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112: lease owned by peer
Jun 25 11:43:24 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112: lease owned by peer
Jun 25 11:43:38 dhcpd: DHCPREQUEST for 10.112.1.1 from 00:19:d1:4d:03:f8 
via em2.112: lease owned by peer
Jun 25 11:43:39 dhcpd: DHCPDISCOVER from 00:19:d1:4d:03:f8 via em2.112: 
load balance to peer partner
Jun 25 11:43:40 dhcpd: DHCPREQUEST for 10.112.2.201 (10.112.0.104) from 
00:19:d1:4d:03:f8 via em2.112: lease owned by peer

> 2) I think something with your config is broken. If I were to [wildly] 
> guess, it's a physical/network layer issue.
> 3) I have a very small setup with 100+ clients, and it certainly 
> doesn't work this way for me.
>
> There are some issues when a single server is up and in 
> "communications interrupted" mode and you've got a tight IP pool and 
> the leases were fairly evenly balanced against both servers. [I've 
> posted, in the past, about an event that was kinda ugly for this 
> client while running a 4.1 version [IIRC]. *However* those problems 
> should be vastly less of a problem with 4.2+ - and you're not having 
> an issue with communications interrupted anyway.
>

> I am having an issue with communications interrupted. When I pull the 
> ethernet cable, both the primary and secondary servers move from 
> normal to  communications-interrupted.
>
> But in your initial post on this thread you said:
>
> > "*After both the primary and secondary
> > had moved from communications-interrupted to normal"
>
> *It can't be both ways. Either they are CI, or in a Normal state. It 
> can't be both.
> Like I said, logs would probably be helpful. [Unless someone else has 
> a lightening bolt moment and can tell you exactly what's wrong without 
> them - but I doubt that.
I hope the logs above help.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.isc.org/pipermail/dhcp-users/attachments/20150625/09e36cb1/attachment-0001.html>


More information about the dhcp-users mailing list