[VoIP] ENUM (Linux DNS) and Linksys WRT54GS

[Chad Perkins]

On 5 Jan 2008 at 12:47, Greg Blakely wrote:
> Even though others seem to disagree, I think that it has something to
> do with DHCP.
> 
> In a static IP situation, your entries in /etc/resolv.conf would
> always be there exactly as you entered them.  This would include your
> ISP's DNS server, and other optional information.

True.  Most consumer grade routers offer their own LAN IP address to DHCP clients 
as DNS server (in addition the DHCP server and default gateway) and perform 
"proxy" DNS, which generally is a good thing as you do not need to keep track of 
DNS server changes, infrequent as they may be (because the router is going to get 
that information as part of it's DHCP client lease from the ISP).

As a result many folks use the routers LAN IP address as the DNS server on 
statically configured machines to keep things clean and simple (clients will behave, 
DNS-wise, the same as DHCP clients as they are using same servers, and they 
don't have to worry about DNS server address changes, etc.).  I fall in this category.
 
> But, by using DHCP, the /etc/resolv.conf is overwritten by whatever
> information your DHCP server provides.  

Agreed.

> If I understand you correctly,
> it is your router that is acting as a DHCP server, and it is handing
> out its own IP address as being the DNS server.

Close.  In addition to running Asterisk, the linux box is the DHCP server (and tftp 
server, I have some Cisco phones that have advanced needs).  The DHCP server 
function is the only thing I took "off" the router.
 
> So, I zero in on the DHCP server.  Two thoughts occur to me.  Either
> (a) the DHCP server doesn't know how to deal with NAPTR DNS resource
> records, 

DHCP clients get their leases from the linux box (the DHCP server), it gives them the 
routers LAN IP address for default gateway and DNS server.  The linux box performs 
no DNS service except for itself.

DHCP servers per se don't do DNS, unless of course it is also a DNS server.  And 
given the way this box is now behaving, the problem seems to affect A records too.

> or, (b) it doesn't have an upstream DNS server that it queries
> that responds in a timely manner.
 
I would say yes to this one, except the Windows clients are configured with the same 
LAN IP address for the DNS server and still work fine.  

I'm about ready to fire up Sniffer Pro and see what the linux box is actually doing on 
the wire and compare that to a working machine!!

Chad
1-955-9924

 
> > -----Original Message-----
> > From: voip-bounces at ckts.info [mailto:voip-bounces at ckts.info] 
> > On Behalf Of Chad Perkins
> > Sent: Saturday, January 05, 2008 10:57 AM
> > To: Voice Over IP Tandem for Analog Switches
> > Subject: Re: [VoIP] ENUM (Linux DNS) and Linksys WRT54GS
> > 
> > The problem seems to be in Linux.  I think what's happening 
> > is that Enumlookup (a DNS query) is timing out before getting 
> > an answer (Asterisk does hang for a minute on the EnumLookup).
> > 
> > The larger problem I think is even pinging is very slow by name
> > (i.e. std.ckts.info).  Connections made by IP address are just as
> > fast as before, even to the same site(s).  This problem seems to be
> > effect all applications that use DNS, except nslookup!!?
> > 
> > Chad
> > 
> > On 5 Jan 2008 at 1:02, Greg Blakely wrote:
> > > Chad,
> > > I can email you a copy of my "dc" macro.  It works on those 
> > versions 
> > > of Asterisk 1.4 that don't have a broken ENUM function.  
> > Let me know.
> > > Greg
> > 
> > > > -----Original Message-----
> > > > From: voip-bounces at ckts.info [mailto:voip-bounces at ckts.info] On
> > > > Behalf Of Chad Perkins Sent: Friday, January 04, 2008 10:54 PM
> > > > 
> > > > I'm in day 3 of not being able to make calls on CNET due to a
> > > > failure of Linux DNS after a reboot of the box and replacing the
> > > > VeriZon DSL router with a WRT54GS...
> > > > 
> > > > Tonight I flashed the firmware on the Linksys from 1.50.6 to
> > > > 1.52.2 (the latest?) to no avail.
> > > > 
> > > > I'm off to bed now, but if any you Linux "gurus" think you can
> > > > figure how how to fix this I'd love to hear from you tomorrow
> > > > (1-955-9924)! Chad