[SOLVED] iPhone push problems with Zimbra Mobile

[Dirk]

Push email is a wonderful thing when it works, and seemingly impossible to debug when it does not.

I'm using Zimbra 5.0.16 and iPhone 3GS & 3G with version 3 firmware. Zimbra mobile is enabled and the phones are configured to use exchange active sync.

Sometimes they work great, other times they dont. I can have the phone in my hand, connected to the wireless lan, in the same building as the zimbra server and a change made to the account on the web server does not reflect on the phone. They you try the same test another time and as soon as you delete a mail, it's instantly removed from the phone's screen.

I know the /opt/zimbra/sync.log will show the activity here but it I cant read it. Is there an easy way to diagnose these issues. Is there a way to ask zimbra what phones are connected to it?

[uxbod]

Dirk, was this happening when you were on iPhone O/S V2 ? I have upgraded to V3 on a 3G and have not experienced any issues thus far. Though no doubt that has just tempted fate How are you finding the 3GS ?

[Dirk]

Yes, it was also intermittant with the phones at version 2.

I'm liking the new 3GS a lot, the speed boost is quite noticable and video recording is a useful addition.

[Dirk]

I've done some more testing and I now know what is causing the problem, but not how to solve it.

We have a local Zimbra server, accessible on port 443 from the outside world, and from the lan for people in the same building. We also have wifi access points in the building and zimbra can be accessed from those also.

DHCP is configured to give an IP address to local computers and iphones and give our internal DNS server, which has a local ip entry for the Zimbra server.

When the phones are in the outside world, the DNS they see resolves the hostname of our mailserver to our external IP address.

It seems that, when on site and switching between wifi and celular networks, as the phone will go as it goes asleep; the IP it see's for mail.company.com is changing between our internal and external IP addresses.

I doubt I have a unique setup here, so I think I have something set wrong. Does anyone else run a Zimbra server, with iPhones using the exchange protocol and have reliable push while one the same lan as the server?

[uxbod]

Dirk, I have not seen the issues you are describing even though I have the same setup. Whether I am on my own LAN or on Cellular push events work just fine. Do you use a different FQDN on your internal LAN at all ? I use BIND with internal/external views so whether inside/outside of the LAN I am using the same naming.

[Dirk]

Now that I've really started looking for this, I'm quite sure that push is not working on the lan. Here's the config.

DNS A record entry for mail.domain.com to public IP at the domain registrar
MX record to mail.domain.com and the registrar
DNS A record on internal DNS for mail.domain.com to internal IP of zimbra server
MX record on internal DNS to mail.domain.com

Ping mail.domain.com from home and it resolves to the public IP, ping the same name from the computers in work, or the work wifi and it resolves to the internal IP, this is what I'd expect to happen.

A user here had wifi disabled on his phone (no wifi at home) and push worked fine for him. As a test, we enabled the wifi on it so it would connect the the local lan and push stopped working.

The DHCP server onsite sends out IP addresses for the two DNS servers we have onsite here, both windows active directory servers.

I have another installation exhibiting the same symptoms where the only infrastructure difference is a BIND server running on ubuntu instead of the windows DNS.

[MacGuyinNC]

We're facing a similar situation here, with the exception being that we have a flat network. The Zimbra server's IP address inside our LAN is the same as outside.

The specific issues that we are seeing is that some repeating meetings to which people have been invited are simply disappearing off of people's iPhones, while others stay. There doesn't seem to be any rhyme or reason behind it. However, if the meeting is updated via the web client, that usually "kicks it into gear."

Any way we can troubleshoot what's going on? What logs should I look through, and what should I look for?

TIA...

[Dirk]

I've done more testing on this and have established the following test case:

Test 1
iPhone with wifi off and cellular connection on.
Push works.
Uunplug sim card to kill cellular connection
Turn on wifi
Push works

Test 2
iPhone with wifi off and cellular connection on
Push works.
Turn on wifi
Push fails.


In case 1, the sync.log shows that the IP address of the handset changes from the public IP provided by the cellular carrier, to the internal IP provided by our own DHCP server. As a result of the server knowing where the phone is, push continues to work.

In case 2, the server log file shows the public IP address still for the phone, and does not change to the internal IP address.

Now, that would seem to be an issue with the iPhone, rather than the zimbra server, but there is a third case, that of the phone switching between wifi and cellular connecitons while on a lan other than the one local to the zimbra server, such as me being at home and using both my wifi and the cellular network as I walk in and out range; this works fine, push continues to work in this condition.

Could some other people investigate to see if you can replicate these results? This problem means that push does not work for the staff while they are on site.

[Dirk]

Fixed!

I've traced this to what I believe to be a problem with the iphone. When the phone moves between a public and private DNS server, which is what happens when it's on the LAN Wifi and getting local DNS from that, and public DNS from the cellular network; it all goes wrong. The phone, like OSX caches the DNS results and it seems to be this that causes the problem.

I've worked around this by changing the server entry on the phone from the DNS name of the Zimbra server to it's public IP address. Setting it to the address means it does not change. This works fine from outside of the lan of course, but you may need to change a setting on the firewall if applicable, to ensure that the port-forwarding, if used, is functional from inside the firewall.

This can be tested by trying to access your zimbra server from a browser using your external IP address, if it works, then you are good to go.

That's what I've done, and push now works perfectly.

[uxbod]

Glad its working Dirk, but very confused why mine seems to be okay using the FQDN. Hmmm