Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
New Member

RV180W intermitent DNS issues

Hello,

I have a simple setup with a RV180W router (5 users, no domain, no AD, 1 VPN site-to-site).

Everything was working fine during about 1 year. Suddently, last week, internet browsing is slow or giving 404 error on computers.

You can try to load google (or any page) it give 404 error, you try it again it takes 3 minutes to load, you try it 5 sec after, it works.

I'm connected with Remote Desktop externally when doing my tests, the connexion is NOT dropping (while I experience 404 error) which makes me think of a DNS issue.

The router setup hasn't changed before the problem happens (no new computers, no firmware upgrade).

I was on 1.0.1.9 firmware so I tried to update it to the latest 1.0.3.10. That didn't resolve the issue and now i'm having the "100% CPU bug" that is stated in numerous other post. (which I don't care for now)

If I reboot the router, everything works fine for a couple of hours before failing again.

The syslog is showing 0 error, 0 warning, 0 all.

Should I replace the unit ?

Thanks,

Benoit

Everyone's tags (2)
6 REPLIES
Gold

RV180W intermitent DNS issues

Benoit,

When the issue occurs, can you ping google.com? If the name does not resolve to an IP address, that would confirm a DNS issue.

Who is the ISP?

What type of connection is it? (DHCP, Static, PPPoE)

Did the ISP provide a modem/router or just a modem?

Has anyone tested with a PC connected directly to the modem?

Can you ping the WAN IP of the router from the outside when this happens?

If yes, what is the response time?

- Marty

New Member

RV180W intermitent DNS issues

Hi Marty,

Right now, everything is working fine so I can't make some test you're asking.

As soon as the problem comes back i'll answer both of these question :

When the issue occurs, can you ping google.com?

Can you ping the WAN IP of the router from the outside when this happens?

Who is the ISP?  : Cogego (Canada). I've called them and they told me that there's no problem on their side (classic)

What type of connection is it? DHCP

Did the ISP provide a modem/router or just a modem?  It's just a modem and it has been replaced on monday.

Has anyone tested with a PC connected directly to the modem?  No, but I could make the test.

I've done a tracert on google.com last time the issue occurs and it was resolving the name but the response was very slow.

I've also been able to connect to speedtest.net to make a speed test, the page was loading correctly but the speed test couldn't complete giving a timeout error each time.

As soon as the issues comes back, I'll provide more answers.

Thanks,

New Member

RV180W intermitent DNS issues

The problem occurs again this morning.

Here's the response to the 2 unawnsered questions :

When the issue occurs, can you ping google.com? Yes I can ping google.com but the response times are awfull (300ms+).

Can you ping the WAN IP of the router from the outside when this happens? Yes I can sucesfully ping the WAN IP

Thanks for your help

Gold

RV180W intermitent DNS issues

Benoit,

This is starting to look like an MTU issue. Perform an MTU test on a LAN PC:

1) Open the Command Prompt

2) ping 8.8.8.8 -f -l 1472 (You should get replies)

3) If you get good replies, the MTU of the WAN port is correct at 1500

4) If you see "Packet needs to be fragmented but DF set.", run the command again with MTU 1464 instead of 1472. If you get clean replies, try 1466, 1468, etc.

You are looking for the highest even number that gets replies instead of "Packet needs to be fragmented but DF set." Whatever that number is, add 28 to it and assign that number as the MTU on the WAN port.

Under Networking-> IPv6-> IP Mode, make sure it is set to IPv4-only unless you are using IPv6. I have seen Dual-Stack cause issues like you describe in some cases.

- Marty

Bronze

RV180W intermitent DNS issues

I have seen problems like this on my rv016 when teh ISP changed something on their end.

First, try setting your dns servers manually and see if this eliminates the problem.

Does rebooting the router automatically solve the problem?  How long before it starts up again?

Huntsville's Premiere Car and Bike e-magazine: www.huntsvillecarscene.com

Huntsville's Premiere Car and Bike e-magazine: www.huntsvillecarscene.com

Hi,I have the same problem

Hi,

I have the same problem but with another type of router (Cisco 851)

In my case (https://supportforums.cisco.com/discussion/12157351/cisco-dns-server-problem-it-stops-serving-clients) I've saw that Cisco DNS service simply stops resolving the domain queries.

 

Enable the domain debugging and have a look at the way your Cisco box solve the domain requests!

A reboot of the router fix the problem but sometimes a simple chear host * do the trick as well but not always.

 

Regarding the MTU: you can check the MTU for each segment between your router and the DNS server used by Cisco to solve the domain requests.

 

In my case the MTU is the same all the way between me and the external DNS server: I did a MTU discovery from my side to the DNS server and it is all 1492.

I used mturoute for that:

D:\>mturoute.exe -t 208.67.222.222
mturoute to 208.67.222.222, 30 hops max, variable sized packets
* ICMP Fragmentation is not permitted. *
* Speed optimization is enabled. *
* Maximum payload is 10000 bytes. *
 1  -++++++++-++-  host: 192.168.1.1  max: 1492 bytes
 2  ...-.-  host: 10.0.0.1 not responding
 3  +-  host: 10.30.0.225  max: 1492 bytes
 4  +-  host: 213.154.99.21  max: 1492 bytes
 5  +-  host: 213.154.124.7  max: 1492 bytes
 6  +-  host: 212.162.45.41  max: 1492 bytes
 7  +-  host: 4.69.141.30  max: 1492 bytes
 8  +-  host: 4.69.201.137  max: 1492 bytes
 9  +-  host: 4.69.201.114  max: 1492 bytes
10  +-  host: 4.69.163.6  max: 1492 bytes
11  +-  host: 4.69.154.73  max: 1492 bytes
12  +-  host: 195.16.160.78  max: 1492 bytes
13  +-  host: 208.67.222.222  max: 1492 bytes

 

My host uses MTU = 1492 (used DR. TCP to check that). My router uses MTU 1492 because it connects to the ISP via PPoE. So, in my case, the MTU should not be the problem.

PMTUD is also enabled so my host will adjust the MTU in order to pass the segments with lower MTU...

 

598
Views
0
Helpful
6
Replies
CreatePlease to create content