asterisk users - May 2015 - asterisk-users Digest, Vol 130, Issue 14

----- Original Message -----
> From: "Steve Davies" <davies147 at gmail.com>
> To: "Asterisk Users Mailing List - Non-Commercial Discussion" 
> <asterisk-users at lists.digium.com>
> Sent: Wednesday, May 13, 2015 11:39:29 AM
> Subject: Re: [asterisk-users] "Retransmission Timeout" results in
> dropped calls after 32 seconds
> 
> Hi,
> 
> In my experience, all Yealink phones work just fine with Asterisk, we 
> have hundreds (perhaps even low-thousands) out there with customers on 
> Asterisk 1.2, 1.6.2, 1.8 and 11.
> 
> If you are accurately representing the SIP trace on the phone and the 
> SIP trace on Asterisk, then I would strongly suggest a SIP ALG exists 
> in the network between the two devices and that SIP ALG does not 
> understand SIP properly. The two halves simply do not match, so 
> something must surely be interfering.
> 
> In my experience it is often an innocent looking Cisco router. Cisco's 
> SIP implementation is "SIP By Cisco" rather than "RFC
compliant SIP".
> If that is the case Cisco call it a "SIP fixup" and you just need
to
disable it.
> 
> Hope that helps,
> Steve
> 
>Steve,
>That is an interesting point - the server and the phone are both connected
to Netgear switches where I have enabled their "Auto-VoIP" feature,
which
remarks packets based on protocol (SIP, SCCP, etc) for better
QoS:
>http://kb.netgear.com/app/answers/detail/a_id/21758
>I wonder if this remarking process is modifying another part of the packet
too?
>Both devices are on the same subnet, so although these switches do route
traffic as well, that shouldn't be coming into play here.

We had a very specific issue at a client recently with Yealink phones and
Cisco routers. No Yealink we plugged in would pick up an IP from the DHCP
server so it could be configured.

To correct it we had to explicitly turn off LLDP (link layer discovery
protocol) on the Yealinks in order to get them to work on the Cisco'ed
network.

Did not fool around with the Cisco to try and solve the issue, and still
don't know exactly what was going wrong, but it seems defined that using
recent model Yealink phones on a network with a recent Cisco router, either
turn off LLDP on the phones or the router to prevent problems.

The above still did not solve the issues completely, still getting one or
two complaints from this customer every few days which also seem to be
related to the fact of using Yealink phones with a network where a Cisco
router is present... so your milage may vary.

Stefan