Can't ping google.com - DNS only resolving on some sites

RouterOS General
1

I’m at a stage where I know enough about networking for it to be dangerous :stuck_out_tongue: As in I don’t know heaps but I know some. So just get that out at the start.

Now the problem is I can’t ping certain sites from within the router. It seems to be larger sites that I can’t ping and so far that is the only connection I’ve managed to make.

I’ve tried pinging google.com, microsoft.com, wordpress.org, google.co.nz, facebook.com and all of them come back with “while resolving ip-address: could not get answer from dns server”

But examples of sites that do work are this one… So mikrotik.com comes back as normal, xero.com, indelible.co.nz, trademe.co.nz (yes I’m in New Zealand). These as well as pretty much all the sites I own work… And weird that some of them work and some of them don’t. I can ping the IP addresses of all the sites fine, just not domain names. So I guess the problem is DNS specific…?

I’m using a Mikrotik routerboard 750GL for the router with a Draytek Vigor120 modem if that helps…

Thanks in advance for any help :slight_smile:

2

either your DNS server is error, or your ISP redirecting all DNS queries into their DNS server, and also got error

3

Hmmm how might I go about troubleshooting to the next step? Anything I can do on my side without asking the ISP?

4

Try to config the DNS as 8.8.8.8 or/and 8.8.4.4

Those are from google Public DNS

5

I already had 8.8.8.8 as my DNS server but not 8.8.4.4 so I’ve added 8.8.4.4 but still same error and its still not resolving…

6

Also I’ve noticed in the DNS cache when I ping one of the other sites (ie not the main ones that aren’t resolving) it pops it into the DNS cache on the router as it should… But with the other domains that aren’t resolving nothing gets put into the DNS Cache on the router… So i’m really confused… Is there some setting that I just have completely missed that may be causing this problem…

7

What’s your ROS version? There has been issues in the past with this sympton. Update to 5.8 that seems to be pretty stable for normal configs..

8

Oooh I got so excited just then but nah that doesn’t seem to have fixed it, still playing up :frowning: It was 5.5 but is now 5.8

9

it seems like they do redirect your dns queries to their server

10

Hmmm but if I manually change the dns servers on each computer then they can ping through fine… Just through the router it doesn’t work which is proving to be problematic for my Linux server

11

you can try to allow larger than older standard packets. By default it is 512 bytes limitation.

12

Wooo! Thankyou! That did it :smiley: Thanks heaps!!!

13

how does max packet size affect this? so what size is better?

14

My Max UDP Packet Size was at 50 after doing a factory restore… Changed it to 512 now and it’s working sweet…

15

Hi, i am facing the same issue, where can i change the packet size setting?

16

Your UDP packet size is already to 202x default: 4096
Do not resurrect old topics, are irrilevant for your bad config.

17

You are replying to a topic that is 12 years old and refers to a completely different RouterOS version.
You are likely NOT “facing the same issue”.