Internet browsing issues Comcast Business.

pgm554
pgm554 used Ask the Experts™
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Internet browsing issues Comcast Business.
This AM users on three separate static IP network routers lost the ability to browse internet.
I can rdp into all 3 networks ,but can't browse the net from any of them.
Can ping the main Comcast router gateway,but can;t do a tracert.
I can connect to my Exchange server ,but can't send or receive.

Comcast can't get a tech here until Sunday with a new modem.

Any ideas?
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JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
Can you do a hard reset of one router, reset the modem, connect only one computer to the router. Does it work?

Connect the computer to the modem directly. You may need a static IP to do this

Follow up note:  Amongst other things, they may have changed Gateway or DNS or something like that, and the resets above should reset the parameters
>Can you do a hard reset of one router, reset the modem, connect only one computer to the router. Does it work?
i did all that.
No go.
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
If you have done that then for sure it is a Comcast issue (or possibly their modem needs to be replaced).
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WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
Go to http://intodns.com and report any errors back here.

From any computer open an elevated command prompt and type nslookup and put in google.com, amazon.com and share what the results are.

I'd call Comcast and ask what their DNS ip's are and confirm they haven't changed.

Try 8.8.8.8 hardcoded into a NIC DNS entry on a computer and see if you can resolve websites. Report back if you can.
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
This AM users on three separate static IP network routers lost the ability to browse internet.
the probability of these three routers going down at the same time is nearly zero. Although the routers are static I assume they are passing DHCP / DNS to each network. Please confirm. If one DHCP server is providing each static router to pass on then it may be a DHCP problem. Is your entire network hardcoded static IP's? Unlikely but have to ask. DHCP provides a scope which tells each computer what DNS to use. Could also be a DNS issues inside your network. If you configured DHCP on your LAN then you likely (or should be) using DNS along with it. Either of these could be causing the issue as well as they're one point of failure that would affect three different routers. Please share more where you get DNS and DHCP from on your LAN.
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
Most likely since a single computer does not work, it is something Comcast needs to fix
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
Agree it's a single device issue but if they have in-house DNS and DHCP which could be causing the issue then it's not on Comcast's side.
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
A single computer connected to the Comcast modem would work if Comcast would be working and it does not
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
Could be a internal root-hint or forwarding problem on their own DNS.
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
Does the single computer get DHCP info from the LAN and he just connected it directly to the Comcast modem? Can't have two DHCP servers on a network, so if they do have an internal DHCP server this means the DHCP server on the Comcast modem is off which means it wouldn't work. We need more info regarding the network setup. My guess is if you're running three routers it's likely you're running your own DHCP / DNS. My thinking you should be anyway, three separate routers is not the average plug into Comcast out of the box solution.
The Comcast Modem/router is not doing dhcp.
It has a range of static IP's  and their are separate routers for each subnet with a static IP on it's WAN port.

I have  3  separate routers ,each with it's own static IP that are plugged into the Comcast internal switch which has it's own static IP gateway.
Each has port forwarding back to the file servers which are acting as a dns forwarder(I used the SBS wizard to set this up).

I even set up a new router with a new static IP and a laptop to see if I can get out to the internet.
I can ping the Comcast gateway ,no issues.
We had a powerfail Thursday  AM  and it seems to be a delayed  issue.
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
It is possible that the power surge that may have resulted from the power failure may have damaged the modem.  Comcast will need to ascertain.
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
Does nslookup work from the SBS? Since this is managing DNS/DHCP if it's not working here it won't be working downstream. Have you run the fix my network wizard on the SBS?
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
FYI it's not a ping issue it's a DNS issue, instead of pinging IP's run nslookup to determine which device is not resolving the site name to IP.
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
On the SBS you may want to run ipconfig /flushdns and restart the DNS and DHCP servers.
The routers are doing dhcp.
I've tried changing nameservers on one of the routers from Comcast (75.75.75.75) to Google dns to see if there is a difference.
No change.
nsl.PNG
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
Looks like you're not resolving IP4 addresses
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
do ipconfig /all and share the results
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
It is Sunday night. Did Comcast come with a new Modem?  and then does the new Modem work correctly?
Yes ,they did and no,it did not.
Nslookup works sporadically
It's Comcast and it's their issue.
I can't even use a router to use their DHCP on the routers WAN port.
I bought two new routers just to see if it was one of my older routers.
They work fine on my Comcast home network ,but will not work correctly with their Comcast business modem.

I was getting a well ,we go as far as the equipment we own ,so you're on your own line of B$.

EVERYTHING  worked fine until Friday at 11:17 AM.
Now nothing!
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
The tech should have a computer that they can hook up to their ISP modem and show you the results. I suggest you call them and escalate.
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
SBS ideally should use it's own DHCP and DNS, just an FYI. I'm still not convinced why you think it's Comcast. I know it worked at one time but this is irrelevant at this point.
I just turned on ipv6 on one of the routers and things are working.
I've eliminated the sbs ,we're talking a router,their modem and a laptop and it wasn't working.

If that's not Comcast ,then what is?
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
It means that Comcast may only be able to deal with IPv4 although they should be able to deal with / ignore as needed IPv6
WORKS2011Managed IT Services, Cyber Security, Backup

Commented:
Looks like you're not resolving IP4 addresses
Not the exact answer but was definitely moving in the right direction from my previous post. Not resolving IP4 or need to resolve IP6. Either way too bad you didn't look into this earlier, kind of like when I asked you to post ipconfig /all.  

I've eliminated the sbs ,we're talking a router,their modem and a laptop and it wasn't working.
SBS actually works better with IP4 than IP6, allot of known issues with it. You may have issues in the future because although it's working I can't see routers handing off DNS/DHCP as a "best practice". You didn't eliminate the SBS you just got it to work by turning things on and off. Not trying to be harsh about it rather following best practices usually keeps networks running uninterrupted.

Comcast doesn't care, period. Neither does TIme Warner/Spectrum, etc. All they care about is overselling their services to saturate the network and bill out to as many people that will buy the same service from them. They don't care if it doesn't work and they don't care if they change something and it stops working.

Congrats on getting it resolved yourself, waiting on Comcast you still would be waiting (and paying).

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