Failover Peer Issue with Polycom SoundStation IP 6000 Phone

[Simon Hobson]

willieb <will.bashlor at btctelcom.net> wrote:

> Thanks so much for the reply! I stop the service on the second server, then
> the first server stated: "dhcpd: failover peer failover-dhcp: I move from
> normal to communications-interrupted". I'm not sure if this is the same as
> partner down state?

No, they are two different states.

In partner-down state, one server will behave near enough the same as a single server - handling all the IPs in the pools.

communications-interrupted is very different. The server cannot know that the other server is actually down - there are a number of potential network topologies/fault conditions where a client could have communications to/from both servers, but the servers can't communicate between themselves. If a server assumed the other was down and took over the whole range(s), then that would cause some rather serious issues.

To get from communications-interrupted to partner-down requires operator intervention, OR configuring automatic transition (it's not the default) having decided that the risk is acceptable for the given network topology.

I don't actually use failover, but there's been plenty of threads about it over the years. In partner down state, the server will alter it's behaviour in terms of what leases it will service and what lease times it will use - and I think that differs depending on whether the address is currently managed by this server or it's peer. TBH I don't have that detail in my head.

> The lease times are both 7 days. I could easily change this but I don't
> think it will make a difference.

Probably not. But many years ago I had to give up configuring a particular printer (early days of the digital copiers) with DHCP - it would just never accept a lease. Some time later I found out that it only accepted leases that were over 2 years long - met with a "WTF ?" from me ! You have to wonder what's in the mindset of some developers.

> I compared the 2 case captures. Case 1 with 2 servers in a failover
> configuration when the issue is happening, and case 2 with the second
> server's service stopped and the issue is not happening (phone gets IP
> immediately). The only difference I can see between the 2 captures is the
> "DHCP Server Identifier" in the ACK.

Interesting. I would have expected to see differences in lease lengths as well - see above about peer states.

> In case 1 the "DHCP Server Identifier"
> in the ACK is the IP of the second server (which I find odd since split is
> set to 255). But this is also the case with captures using the other model
> phones (i.e. VVX411) that are working fine. Hmmm. In case 2, of course the
> "DHCP Server Identifier" is the IP of the first server, since there is only
> 1 server. For case 1 and case 2 I see the "DHCP Server Identifier" in the
> OFFER messages is that of server 1.

BTW - did you check which server "owns" that lease ?

Simon