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Comcast DNS timeouts 75.75.75.75

Posted on 2012-08-23
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Last Modified: 2012-08-30
Comcast recently had an outage in my area. I never tested this prior to the outage. I am pinging comcast dns  75.75.75.75 and notice timeouts after 5-6 icmp request.

Comcast is telling me this is "normal behavior since it could be saturated" The Tech's told me they also see the packet loss..but no one in the area is complaining..I've called them three times and I can get any better response.

Ever since the initial outage less than a week ago we switched over to our AT&T pipe. But we are reluctant to switch back to our Comcast pipe until we know exactly why we receive time outs to 75.75.75.75 & 75.75.76.76

What do you guys think could be going on?
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Question by:tobe1424
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7 Comments
 
LVL 12

Expert Comment

by:TomRScott
ID: 38325813
Have you tested other IP addresses both inside and outside your local area?

Trace route would give you a few key routers to try.  The problem may be more than just their DNS servers.

If it is just the DNS servers, you could use other DNS servers until the issue is addressed.

 - Tom
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Assisted Solution

by:TomRScott
TomRScott earned 1000 total points
ID: 38325833
I just compared the first Comcast DNS against an AT&T DNS server using continuous pinging (-t).  I had no timeouts with Comcast and only one with AT&T.
I notice that the the Comcast DNS had a little over twice the lag time as AT&T and I'm on a Comcast connection.

If you are having a lot of time-outs, it may be your local connection.  My test is not conclusive, however.

 - Tom
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Expert Comment

by:Dave Baldwin
ID: 38326065
They could be refusing to respond after the first few ICMPs.  The continuous ICMP is not of value to them.  I have Comcast here and the first two ICMPs to 75.75.75.75 timed out on me.  75.75.76.76 responded ok though.
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Author Comment

by:tobe1424
ID: 38326127
yes i have tested other ip addresses. I have a 2600 in back of my Comcast modem...and we are relying on our ISP dns.

i am trying to report the problem to comcast but they simply tell me nothing is wrong. I wish I could contact an individual with a higher rank so he/she can do something about it or relay the issue.
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Author Comment

by:tobe1424
ID: 38326229
aside from the little lag..i don't get plenty of timeouts...here is an example:

>ping 75.75.75.75 -t

Pinging 75.75.75.75 with 32 bytes of data:
Reply from 75.75.75.75: bytes=32 time=28ms TTL=55
Reply from 75.75.75.75: bytes=32 time=18ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=18ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=17ms TTL=55
Reply from 75.75.75.75: bytes=32 time=16ms TTL=55
Reply from 75.75.75.75: bytes=32 time=19ms TTL=55
Reply from 75.75.75.75: bytes=32 time=14ms TTL=55
Reply from 75.75.75.75: bytes=32 time=18ms TTL=55
Reply from 75.75.75.75: bytes=32 time=14ms TTL=55
Reply from 75.75.75.75: bytes=32 time=16ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=40ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=14ms TTL=55
Request timed out.
Reply from 75.75.75.75: bytes=32 time=17ms TTL=55
Reply from 75.75.75.75: bytes=32 time=14ms TTL=55
Reply from 75.75.75.75: bytes=32 time=31ms TTL=55
Reply from 75.75.75.75: bytes=32 time=70ms TTL=55
Reply from 75.75.75.75: bytes=32 time=14ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=19ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=16ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=16ms TTL=55
Request timed out.
Request timed out.
Reply from 75.75.75.75: bytes=32 time=17ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=14ms TTL=55
Reply from 75.75.75.75: bytes=32 time=18ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55
Reply from 75.75.75.75: bytes=32 time=15ms TTL=55

Ping statistics for 75.75.75.75:
    Packets: Sent = 40, Received = 37, Lost = 3 (7% loss),
Approximate round trip times in milli-seconds:
    Minimum = 14ms, Maximum = 70ms, Average = 18ms
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Accepted Solution

by:
Dave Baldwin earned 1000 total points
ID: 38326260
I don't think they will do anything about it because ICMP is not the service they are providing there.  It is probably a very low priority service like it is most places.  If they are full up with DNS requests, they probably just drop ICMP requests.
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Expert Comment

by:TomRScott
ID: 38326359
I concur, ICMP is a low priority.  Some networks disable it entirely except for their own IT folks when they need it.

Unless you have some other issue, the number of time-outs you show is not a big deal.

And, the lag look great!

 - Tom
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