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My Linksys WRT54GS router is losing its DNS configuration ..

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Anonymous
August 24, 2005 12:21:04 PM

Archived from groups: alt.internet.wireless (More info?)

Hi everybody,

I am using a Linksys WRT54GS Wifi router under Windows XP SP2 and have
the following problem :

My DSL provider modem works in DHCP => my IP address always stays the
same but my provider DNS addresses can change several time a day (I
suppose that my provider use a load balancing system which implies that
the DNS addresses changes)

My router is also configured in DHCP.
When I type "ipconfig /all", I can see that my IP address will be
automatically renewed in 24 hours.
Consequently, when my provider DNS addres changes, my router will not
automatically update so name resolution fails on my computer.

Then, I have to manually connect on the router and request it to
request the new DNS addresses in order to solve the problem.
But I would the router to do this automatically.

Is there something I miss in the router configuration ?
Otherwise, is there a way to push the new DNS entries from my DSL
modem to the router ?


Thanks in advance for your help.
Anonymous
August 24, 2005 1:09:47 PM

Archived from groups: alt.internet.wireless (More info?)

On 24 Aug 2005 08:21:04 -0700, for.fun@laposte.net wrote:

>Hi everybody,
>
>I am using a Linksys WRT54GS Wifi router under Windows XP SP2 and have
>the following problem :
>
>My DSL provider modem works in DHCP => my IP address always stays the
>same but my provider DNS addresses can change several time a day (I
>suppose that my provider use a load balancing system which implies that
>the DNS addresses changes)

Are you sure about that? Such a system might not work even with a
directly connected PC. The way DHCP works is that the client is
responsible for obtaining the IP/DNS/Gateway addresses. There's no
way for the DHCP server to "force" the client to change IP's.
(Exception: Methinks PPPoE and PPPoA can force a change by initiating
a disconnect, but I'm not sure). The key is the lease time. The
client and the router will issue a DHCP lease renewal in half the
lease time. The minimum lease time is 1 hour, so your ISP can
theoretically juggle DNS servers every 30 minutes.

>My router is also configured in DHCP.
>When I type "ipconfig /all", I can see that my IP address will be
>automatically renewed in 24 hours.
>Consequently, when my provider DNS addres changes, my router will not
>automatically update so name resolution fails on my computer.

Wrong. The lease time displayed by your Windoze machine is the lease
time of the DHCP server in the WRT54G router, not that of the ISP's
DHCP server. In addition, the WRT54G has a nifty DNS cacheing server
built in. The DNS server IP on your Windoze machine should be the IP
address of the router (192.168.1.1) and should not change. What's
important is the lease time on the status page of the WRT54G, not the
Windoze client.

>Then, I have to manually connect on the router and request it to
>request the new DNS addresses in order to solve the problem.
>But I would the router to do this automatically.

Questions:
1. Are you sure your ISP juggles DNS servers? I don't know of any
ISP that does this. The load on DNS servers is rarely high enough to
justify a load balancing scheme.
2. Who is your ISP? I wanna try nslookup on their servers and see
what they're really doing.
3. Are you sure that you're using DHCP and not PPPoE or PPPoA? These
handle IP updates differently from DHCP.

>Is there something I miss in the router configuration ?

The lease time on the status page of the WRT54G.

>Otherwise, is there a way to push the new DNS entries from my DSL
>modem to the router ?

I don't think so (not sure).

>Thanks in advance for your help.

--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
AE6KS 831-336-2558
Anonymous
August 24, 2005 6:34:36 PM

Archived from groups: alt.internet.wireless (More info?)

Thanks for all your explanations.
Here are my replies to your questions.


Jeff Liebermann a écrit :

> 1. Are you sure your ISP juggles DNS servers? I don't know of any
> ISP that does this. The load on DNS servers is rarely high enough to
> justify a load balancing scheme.

I am pretty sure they do it.
This morning, I looked at the router status page and saw the 2 DNS IP
entries. This afternoon, my computer was unable to resolve any host
name.
In order to solve the problem, I forced the router to get the
configuration again from the DSL modem and I noticed that the second
DNS entry changed (and I was able to resolve the host names)


> 2. Who is your ISP? I wanna try nslookup on their servers and see
> what they're really doing.

This is Free (a French ISP) and the Web site is "www.free.fr"


> 3. Are you sure that you're using DHCP and not PPPoE or PPPoA? These
> handle IP updates differently from DHCP.

I double-checked this and I am sure that I am using DHCP.


> The lease time on the status page of the WRT54G.

I did not find the lease information on the router status page. Perhaps
I should upgrade the BIOS ?
Related resources
Anonymous
August 25, 2005 7:43:17 AM

Archived from groups: alt.internet.wireless (More info?)

On 24 Aug 2005 14:34:36 -0700, for.fun@laposte.net wrote:

>> 1. Are you sure your ISP juggles DNS servers? I don't know of any
>> ISP that does this. The load on DNS servers is rarely high enough to
>> justify a load balancing scheme.

>I am pretty sure they do it.
>This morning, I looked at the router status page and saw the 2 DNS IP
>entries. This afternoon, my computer was unable to resolve any host
>name.
>In order to solve the problem, I forced the router to get the
>configuration again from the DSL modem and I noticed that the second
>DNS entry changed (and I was able to resolve the host names)

OK. I guess they really are juggling DNS addresses. That's a first
for me. I wonder if this is some kind of scheme to keep free users
from staying connected and idle for too long?

>> 2. Who is your ISP? I wanna try nslookup on their servers and see
>> what they're really doing.
>
>This is Free (a French ISP) and the Web site is "www.free.fr"

Nice mess. Their backup nameserver (freens1-l.free.fr) can't even
resolve their own domain (free.fr). At least the primary nameserver
works correctly.

NSLookup shows only two authoritative nameservers for free.fr:
freens1-a.free.fr A (Address) 213.228.0.82 (main)
freens1-l.free.fr A (Address) 213.228.0.198 (backup)
I've been pounding on these most of the last 4 hours and they are not
changing. However, free.fr may have other nameservers hidden behind
their firewall for their own customers. Lookups show a 7 day expire
so there's no way they are juggling the public nameservers with that
long a DNS cache.

>> 3. Are you sure that you're using DHCP and not PPPoE or PPPoA? These
>> handle IP updates differently from DHCP.
>
>I double-checked this and I am sure that I am using DHCP.

>> The lease time on the status page of the WRT54G.
>
>I did not find the lease information on the router status page. Perhaps
>I should upgrade the BIOS ?

I'm using Sveasoft Alchemy firmware which gives me a command line
interface for the unerlying Linux operating system. I can see the
file:
/tmp/udhcpd.leases
but it's cryptic garbage. I can't seem to figure out how to display
the current DCHP cache with lease times. Since I have a static IP on
the WAN side, I don't think dumping my file will show anything. I'll
do some digging to see if I can extract the values.

Meanwhile, methinks just using some other ISP's DNS server may be the
only way to work around the problem.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# http://802.11junk.com
# jeffl@comix.santa-cruz.ca.us
# jeffl@cruzio.com AE6KS
Anonymous
August 25, 2005 8:09:23 AM

Archived from groups: alt.internet.wireless (More info?)

On Thu, 25 Aug 2005 03:43:17 GMT, Jeff Liebermann
<jeffl@comix.santa-cruz.ca.us> wrote:

>I'm using Sveasoft Alchemy firmware which gives me a command line
>interface for the unerlying Linux operating system. I can see the
>file:
> /tmp/udhcpd.leases
>but it's cryptic garbage. I can't seem to figure out how to display
>the current DCHP cache with lease times. Since I have a static IP on
>the WAN side, I don't think dumping my file will show anything. I'll
>do some digging to see if I can extract the values.
>
>Meanwhile, methinks just using some other ISP's DNS server may be the
>only way to work around the problem.

Duh... Run:
ifconfig
on the WRT54G, which should show the lease times. Mine doesn't show
because of the static IP address on the WAN port.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# http://802.11junk.com
# jeffl@comix.santa-cruz.ca.us
# jeffl@cruzio.com AE6KS
Anonymous
August 26, 2005 4:56:33 AM

Archived from groups: alt.internet.wireless (More info?)

Thanks again for all your investigations.


> NSLookup shows only two authoritative nameservers for free.fr:
> freens1-a.free.fr A (Address) 213.228.0.82 (main)
> freens1-l.free.fr A (Address) 213.228.0.198 (backup)
> I've been pounding on these most of the last 4 hours and they are not
> changing. However, free.fr may have other nameservers hidden behind
> their firewall for their own customers. Lookups show a 7 day expire
> so there's no way they are juggling the public nameservers with that
> long a DNS cache.

Do you mean that I can statically define these 2 nameservers in my
router configuration.
If so, it would solve my problems !


> Meanwhile, methinks just using some other ISP's DNS server may be the
> only way to work around the problem.

Do you know any reliable DNS public server ?


> I'm using Sveasoft Alchemy firmware which gives me a command line
> interface for the unerlying Linux operating system.

I have heard of this firmware and it sounds good.
You say you are getting a command line interface in Linux.
I know that the firmware is supposed to be run by the router : since I
am running Windows XP SP2, can you just confirm that it will be OK for
me (I will get the command line interface as well under XP)


> Duh... Run:
> ifconfig

I will install Sveasoft and tell if it works.
Anonymous
August 26, 2005 12:49:27 PM

Archived from groups: alt.internet.wireless (More info?)

On 26 Aug 2005 00:56:33 -0700, for.fun@laposte.net wrote:

>> NSLookup shows only two authoritative nameservers for free.fr:
>> freens1-a.free.fr A (Address) 213.228.0.82 (main)
>> freens1-l.free.fr A (Address) 213.228.0.198 (backup)
>> I've been pounding on these most of the last 4 hours and they are not
>> changing. However, free.fr may have other nameservers hidden behind
>> their firewall for their own customers. Lookups show a 7 day expire
>> so there's no way they are juggling the public nameservers with that
>> long a DNS cache.

>Do you mean that I can statically define these 2 nameservers in my
>router configuration.
>If so, it would solve my problems !

No. That would be so nice, but the stock firmware for the WRT54G
can't do it. I just tried it.

2nd best is the Sveasoft firmware has provisions for adding a "Local
DNS" nameserver but that apparently has to be on the LAN side, not the
WAN. It's on the "Basic Setup" page. I just shoved another local
nameserver into the "Local DNS" field. The "Status" page set this
nameserver as the primary DNS server, leaving the other two DNS
servers to be set via DHCP. This will work if Linksys has the same
feature.

3rd best is to setup your Windoze machines for DHCP or static IP
addresses, and just set your DNS server to the two free.fr server
IP's. Unlike the WRT54G, Windoze allows you to use DHCP for the IP
address, but static (manually set) IP's for the DNS fields. This
bypasses the DNS cache in the router, but you probably won't notice
the difference.

>Do you know any reliable DNS public server ?

Do I have to do ALL the work? You should find a DNS server that is
physically close to your location. I'm not familiar with France or
French geography and therefore cannot offer a guaranteed solution.

Find another local French ISP. Then, to to:
http://www.dnsstuff.com
and plug their domain name into the "DNS Lookup" box on the upper
right. (Try it with free.fr first). Select "NS" for nameserver.
Then go down to the "Click here to check that all DNS servers are
reporting the same results" and look at the latency in msec. For
cable or DSL, it should be less than about 50msec to be considered
useful. I'm getting about 110msec from France to California which is
NOT fast.

>> I'm using Sveasoft Alchemy firmware which gives me a command line
>> interface for the unerlying Linux operating system.
>
>I have heard of this firmware and it sounds good.

Recommended:
http://www.sveasoft.com/content/view/3/1/
You may want to spend $20 and get Talisman, which I'm told is better.
I haven't had time to try it.

>You say you are getting a command line interface in Linux.

Yes, using Alchemy, not the stock Linksys firmware. You telnet or use
SSH2 to connect to the router from your Windoze box and you get the
Linux (Bash) shell prompt. If you're not familiar with running Linux
from the command line, this may be a learning experience.

>I know that the firmware is supposed to be run by the router : since I
>am running Windows XP SP2, can you just confirm that it will be OK for
>me (I will get the command line interface as well under XP)

Any computer or operating system that can run telnet or some SSH
client such as Putty will work. However, I can see that you need to
do some studying and get some experience with Linux before you try
Learning by Destroying(tm). I suggest you download or borrow one of
the Linux "Live CD" distributions. This lets you boot Linux on your
desktop without actually installing anything on the hard disk. There
are also versions that boot from a floppy disk such as Trinux. When
you're comfortable with the shell command line, then you can safely
destroy your router.

>I will install Sveasoft and tell if it works.

Good luck.

--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
AE6KS 831-336-2558
Anonymous
August 26, 2005 4:42:14 PM

Archived from groups: alt.internet.wireless (More info?)

Thanks a lot Jeff.
Thanks to you, I now hav all the usefull information I need to set my
Linksys router properly.

Have a nice Week-End.


Jeff Liebermann a écrit :

> On 26 Aug 2005 00:56:33 -0700, for.fun@laposte.net wrote:

> Good luck.
>
> --
> Jeff Liebermann jeffl@comix.santa-cruz.ca.us
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> AE6KS 831-336-2558
!