Understanding my network

[Arthur Dent]

On Wed, 2012-08-29 at 19:47 -0500, Dale Dellutri wrote:
> On Wed, Aug 29, 2012 at 2:40 PM, Arthur Dent
> <misc.lists at blueyonder.co.uk> wrote:
> >...
> > So here's the thing - and I don't remember having this problem with F15
> > (or previous):
> > I can access my mail using a client on another machine in my network if
> > I configure it to use 192.168.2.2, but for my mobile devices I configure
> > the email client to point to example.org. If I am outside of my network
> > they can access mail fine, but if I am at home and they are connecting
> > via my own wi-fi... no joy...
> 
> It looks like it has something to do with your home router.  It seems to
> be having trouble routing packets which are meant for itself but coming
> from inside the lan.
> 
> Do you have a SOHO router on your lan (separate from your server), or
> is your home server also doing the NAT/NPT routing for your lan?
> 
> When your mobile is at home, it has an IP addr on your lan: 192.168.2.6
> for example.  When it sends something to example.org:993, it first uses
> DNS to change it to an IP addr: 123.456.789.123 in your example.  Then
> it sends the request to the router to get to the internet.  But that's the
> router's own IP addr (because it IS example.org).  So the router ought to
> just use the request internally and deal with it correctly.
> 
> If you have a separate SOHO router did it change lately?
> 
> If your home server is the router, then, of course, it has changed, and
> something isn't working properly.  However, I can't help you any further
> because I've never used a server as a router for a lan.
> 
> (But note that your iptables output shows rules in the FORWARD chain,
> but no packet traffic (those zeroes at the beginning of each line).)

Hmmm....

I am still somewhat mystified. I have a Belkin F5D8233-4v3 wireless
router which has not (as far as I know) been altered since I set it up
3-4 years ago.

With all previous versions of Fedora it "just worked". Poking around in
the settings I can see no option specifically to turn on or off NAT.
However, whilst in there I decided to "reboot" the router. That *seems*
to have done the trick.

I am not wholly satisfied yet however. My main mobile device is an Apple
iPhone 3GS. I find that now that I have rebooted the router I can
sometimes access my mail from within my network (and the iPhone
configuration obviously points to "example.org"), but with the standard
Apple email client I often get a "checking for mail" message with the
network activity icon rotating furiously, but no update of mail. Then
sometimes it will work. I did NOT have this problem before.

However, on the same phone I happen to have another email client
(ibisMail) which (with exactly the same settings) works just fine...

Since rebooting the router my wife's iPad also now seems to work fine.

So I guess it was the router that was the problem and rebooting it seems
to have fixed it. I need to look at my iPhone a bit more closely, but
for the moment I think we have have solved this.

Thank you to everyone who helped. I am not a newbie, but in many areas
(networking especially!) my level of expertise is woefully inadequate
and I really appreciate the helpful support I get from this mailing
list.

Mark
 
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