Connectivity
Connectivity and managing Your Comcast Business network
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Occasional Visitor

IPv6 working but not IPv4

Our service stopped working yesterday at about 3:30pm EDT. When I do a tracert it dies 4 hops out. So I went into the computer room and connected a laptop up directly to our DPC3939B. When I am connected directly I can browse some websites but most don't work. On further inspection I noticed that only IPv6 sites work. IPv4 only sites are failing.

 

When I do a tracert with IPv6 to saw www.comcast.net it works. But a tracert with IPv4 fails on the same hop that it fails when running though our own in house router.

 

Here are the traceroutes:

 

Using IPv6:

tracert -6 www.comcast.net

 

Tracing route to a1526.dscg.akamai.net [2600:1402:14::48f6:3873]
over a maximum of 30 hops:

1 3 ms 8 ms 9 ms 2601:346:404:9200:bcd1:65ff:fe8e:3b6b
2 15 ms 16 ms 14 ms 2001:558:5008:3f::1
3 25 ms 18 ms 27 ms Te0-2-0-14-sur04.southside.fl.jacksvil.comcast.net [2001:558:192:ff81::1]
4 27 ms 25 ms 19 ms te-0-14-0-5-ar02.westside.fl.jacksvil.comcast.net [2001:558:190:115::1]
5 46 ms 33 ms 28 ms be-33489-cr02.56marietta.ga.ibone.comcast.net [2001:558:0:f7cc::1]
6 37 ms 42 ms 37 ms he-0-12-0-1-pe04.56marietta.ga.ibone.comcast.net [2001:558:0:f62d::2]
7 23 ms 33 ms 38 ms 2001:559::af2
8 25 ms 37 ms 31 ms 2600:1402:14::48f6:3873

 

And again using IPv4:

tracert -4 www.comcast.net

Tracing route to a1526.dscg.akamai.net [184.26.136.64]
over a maximum of 30 hops:

1 7 ms 10 ms 7 ms 10.192.10.1
2 12 ms 10 ms 20 ms 96.120.21.129
3 17 ms 17 ms 17 ms Te0-2-0-14-sur04.southside.fl.jacksvil.comcast.net [68.86.171.249]
4 * * * Request timed out.
5 * * * Request timed out.
6 * * * Request timed out.
7 * * * Request timed out.
8 * * * Request timed out.

 

What is really odd is the DPC3939B web interface has some trouble shotting tools. One of them is a traceroute which can run IPv6 or IPv4. Here is an IPv4 tracert using the DPC3939B web interface:

 

Status: Complete !
1: 10,10,10 96.120.21.129 96.120.21.129
2: 20,20,20 Te0-2-0-15-sur04.southside.fl.jacksvil.comcast.net 68.86.171.253
3: 70,10 te-0-11-0-9-ar02.westside.fl.jacksvil.comcast.net 69.139.222.169
4: 20,30,20 be-33489-cr02.56marietta.ga.ibone.comcast.net 68.86.95.49
5: 30,20,30 he-0-11-0-0-pe04.56marietta.ga.ibone.comcast.net 68.86.89.90
6: 30,40,20 50-248-118-218-static.hfc.comcastbusiness.net 50.248.118.218
7: 20,20,30 a184-26-136-112.deploy.static.akamaitechnologies.com 184.26.136.112

 

It completes the trace with no problem. But you can see it takes a different route early on in the trace. When connected directly to the CG my laptop dies at Te0-2-0-14-sur04.southside.fl.jacksvil.comcast.net but when I do an IPv4 trace from the web interface it passes through Te0-2-0-15-sur04.southside.fl.jacksvil.comcast.net.

 

Any ideas? ComCast hasn't been able to help us yet and who knows when they will show up to help. Our EDI orders aren't comming in or out, our emails are not coming or going, our VPN to one of our warehouses is down so they are unable to deal with orders. This is a big deal for us. Our customers are fining us for not handling the EDIs so this is going to get expensive fast.

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2 ACCEPTED SOLUTIONS

Accepted Solutions
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Community Manager
Community Manager

Re: IPv6 working but not IPv4

Hi Noel.  I checked the IPv4 IP address assigned to the device associated with this account.   That IP scope had a dual assignment on the network. That issue has been corrected.  Please verify that you are now able to connect to the Internet. 

 

Thank You

View solution in original post

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New Member

Re: IPv6 working but not IPv4

I had this same problem, i solved it by calling tech support and having them assign me a new static IP. Solved in less than 20 mins including hold time. Might not be an option for everyone, but it works.

View solution in original post

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6 REPLIES 6
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Community Manager
Community Manager

Re: IPv6 working but not IPv4

Hi Noel.  I checked the IPv4 IP address assigned to the device associated with this account.   That IP scope had a dual assignment on the network. That issue has been corrected.  Please verify that you are now able to connect to the Internet. 

 

Thank You

View solution in original post

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Occasional Visitor

Re: IPv6 working but not IPv4

You are the man John!!! I've been getting the run around for 2 days!! We finally got two upper level guys (one was the Technical Operations Supervisor) out to our site to look at our problem. First I demotrated with my laptop connected to the CG that a trace to www.comcast.net via IPv6 worked perfect and that IPv4 failed. Then I showed him that I could do a sucsesful trace to 8.8.8.8 via the CG web interface. Then they said, "well have you tired a trace to 8.8.8.8 with your laptop". I said yeah and then went to demostrate and to my suprise it worked. Hahaha. So then I did a trace to www.comcast.net and it worked too. We were all confused about why it magically started working. I just looked at some timestamps and it started working about the time you posted this. So it turns out you are our hero! Smiley Happy

 

 

So a big thanks goes to you John! We've got 100 people at our office and they were all chearing when they started seeing emails coming in.

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Community Manager
Community Manager

Re: IPv6 working but not IPv4

Hi Noel.  Thanks for the follow up.  I apologize the delay in resolving this issue.  Please let me know if additional assistance is needed.

 

Thank You 

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New Member

Re: IPv6 working but not IPv4

One of our customers are seeing a similar problem - Could you see if it is the same problem? CR-491-593-732

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New Member

Re: IPv6 working but not IPv4

Hello there--one of my clients is also seeing this beginning Monday. Rebooting the comcast router seems to stop it for a while. It seems to be that IPv6 addresses are being handed out but not IPv4. Static IPv4 addresses with static DNS entries are fully functional. Expanded the DHCP range as well. 

I've seen this at another client and was only able to permanently stop this behavior by putting in a third-party router and getting the comcast router put in passthrough mode. I'm hoping we won't have to do this here as well. 

 

An added wrinkle--the client is having their cable modem replaced tomorrow as they switch to a higher speed, so all this might be resolved with new hardware. But perhaps you can check the iPv4 pool as you did with the above poster. 

 

This is a SMC Networks device

Hardware Version1.01
  
Firmware Version3.1.6.56

 

customer # 8778104017099360

 

 

thanks!

 

 

 

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Highlighted
New Member

Re: IPv6 working but not IPv4

I had this same problem, i solved it by calling tech support and having them assign me a new static IP. Solved in less than 20 mins including hold time. Might not be an option for everyone, but it works.

View solution in original post

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