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I have suffered through the last week trying to get my internet running correctly after trying to upgrade to GIGABLAST.
If you don't need the bandwidth, DON'T DO IT!
For the most part, COX is offering ahead of having it working correctly. My connection had always been rock solid until I upgraded. I never was able to get more than 500mps and my speeds were also all over the map once I went to DOCSI3.1. Sometimes under 100mps.
If you call for customer support, always ask for level 2 techs. The level 1 techs are worthless. Their level 2 techs are for the most part knowledgable and courteous. But I also found that they all have very differing opinions of the problems but they all agree that Gigablast is not happening.
If they have to send out outside tech, DON'T DO IT!!! unless they will send out direct employee. Their sub-contractors are worthless and cause more problems and no solutions. In most cases they have no knowledge of networking or equipment. They only can test lines. They are dangerous. COX should be ashamed of being represented by these people!