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New Member

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8 Messages

Friday, March 8th, 2024 2:02 PM

DNS lookup returning wrong ip's

We're getting incorrect DNS responses.  I have 5 static ips.  My systems all use Google (8.8.8.8 and 8.8.4.4)  for DNS resolution.  However, the gateway router uses Comcast DNS (75.75.75.75, and 75.75.76.76)  There seems to be no way to change the DNS used on the router.  We also run FIOS.  My guess is that the gateway is using Comcast DNS for resolution, as no matter how we change which servers are used by NSLookup the answers all come out wrong, while the same queries on FIOS for all the same servers return correct answers.  (We can't check the Comcast DNS servers from FIOS as they refuse to answer.)

 The correct addresses for googlegroups.com are:

googlegroups.com        internet address = 142.251.167.103
googlegroups.com        internet address = 142.251.167.104
googlegroups.com        internet address = 142.251.167.147
googlegroups.com        internet address = 142.251.167.105
googlegroups.com        internet address = 142.251.167.106
googlegroups.com        internet address = 142.251.167.99
googlegroups.com        AAAA IPv6 address = 2607:f8b0:4004:c1d::63
googlegroups.com        AAAA IPv6 address = 2607:f8b0:4004:c1d::6a
googlegroups.com        AAAA IPv6 address = 2607:f8b0:4004:c1d::67
googlegroups.com        AAAA IPv6 address = 2607:f8b0:4004:c1d::68
googlegroups.com        MX preference = 10, mail exchanger = alt1.gmr-smtp-in.l.google.com

However, no matter which DNS server I point to on any of my Comcast IPs, the addresses returned are: 

googlegroups.com        AAAA IPv6 address = 2607:fc50:3000:2::1b
googlegroups.com        AAAA IPv6 address = 2607:fc50:3000:2::55
googlegroups.com        internet address = 104.225.8.29
googlegroups.com        internet address = 104.225.8.28

Note that not only are the ip addresses wrong, but no MX records are returned at all, which means that mail servers on those systems cannot send mail to googlegroups.com.  

Please tell me how to change the DNS servers on the gateway, or what else to do to resolve this issue. Thank you.

Official Solution

Official Employee

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294 Messages

4 months ago

 

wharr, Thanks for clarifying. May I ask so kindly what it is you are trying to do? As internal networks vary so drastically from business to business, we can only provide our expertise and basic troubleshooting for our equipment or wiring and reverse DNS requests. Please note, the DNS for your Comcast modem does not have the capability of being modified. If you would like that type of control, you may need to purchase your own modem/router device. 

 

(edited)

New Member

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8 Messages

Sorry, odd interface, didn't see this response.  Please tell me what you see if you set your DNS server to 75.75.75.75 and request the ip address for googlegroups.com.  Specifically, if you use NSLOOKUP and SET TYPE=any so you get all the records.  I believe that that DNS Server is returning incorrect information.  Thank you.  (I cannot test this, as that server does not accept connections from other networks.)

New Member

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8 Messages

What I'm trying to do is to send email to googlegroups.com from our mail servers.  It fails because no MX record is found (MX records exist for googlegroups.com as I previously provided), and the A records returned are incorrect.  This happens no matter what DNS servers are set in our systems and in the client side of the Comcast router.  Those same DNS servers on a different provider return the correct entries.  On the Comcast network they do not.  The only common element of the failures is the DNS specification in the router (75.75.75.75 and 75.75.74.74) which I cannot test from other networks.

Official Employee

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42 Messages

Thank you for clarifying are you using Office 365? As to update any information for your domain name would need to go through Cloud Solutions support.

New Member

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8 Messages

No we are not using Office 365.  We are a small ISP and run multiple servers around the world.  We run our own mail servers on many machines. It is only on the Comcast network that the ip address for googlegroups.com is returned incorrectly.  Can you do the test I requested?

Official Employee

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42 Messages

Thank you,

My team is here to help and to best assist you with further investigating/troubleshooting this, please send us a private Direct Message. To send a "Peer to peer" / "Private Direct message" message to "Comcast Business":

 

 

• Click "Sign In" if necessary

• Click the "Peer to peer chat" icon or https://forums.businesshelp.comcast.com/peer-to-peer-chat

• Click the "New message" (pencil and paper) icon

• The "To:" line prompts you to "Type the name of a person". Instead, type "Comcast Business" there

• - As you are typing a drop-down list appears. Select "Comcast Business" from that list

• - An "Comcast Business" graphic replaces the "To:" line

• Type your message in the text area near the bottom of the window

• Press Enter to send it

Official Employee

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294 Messages

4 months ago

 

@wharr , Thanks for visiting Comcast Business over our forums page for help changing the DNS server on the gateway modem. I understand the concern with getting those wrong IPs returned on those DNS responses and appreciate you for sharing these details. We are the right place to go for assistance. Can you tell us if you're noticing any internet service issues? Just in case you aren't already aware, we can create a reverse DNS for your static IPs on our end. Is this what you're referring to with wanting to know how to change the DNS servers on the leased gateway? 

 

(edited)

New Member

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8 Messages

No, there are no internet service issues, and no, reverse dns is not what the issue is.  Please read the question carefully.  The DNS response is incorrect for _one_ address: googlegroups.com.  As far as we can tell, the DNS response is correct for all other domain names.

Because the only common factor in all the tests so far are the DNS servers specified in the gateway, those appear to be the problem.

Contributor

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27 Messages

This sounds like SecurityEdge doing its DNS hijacking. Turn it off (you probably aren't using it on purpose, I've never encountered anyone yet who has.)

(edited)

New Member

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8 Messages

Thanks for the idea, I don't see how to turn SecurityEdge off.  Firewall security in the router is set to minimum.

Official Employee

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16 Messages

If you subscribe to SecurityEdge, you can visit our 'Manage Comcast Business SecurityEdge™ Extended Coverage Settings' support page on how to manage the service. 

New Member

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8 Messages

Thanks, doesn't seem to help.