I do not recall exactly when I bought my first AirPort Extreme base station. It was probably sometime around late 2009 or early 2010, when I moved into my house. I upgraded from the 5th generation and added a 6th generation model in 2014. Within the last week, with no change in configuration what-so-ever, I began receiving the follow error message when I tried to access usps.com.
You don’t have permission to access “http://www.xfinity.com/” on this server.
Let me go through my Network Setup. I have a 5th Generation AirPort Extreme that is directly connected to my cable modem. Connected to this is a 5 port switch in my second bedroom/office. Connected to this is a 6th Generation AirPort Extreme. The two AirPort Extremes are connected via Bridge Mode, where the 6th Generation AirPort does not do any DHCP serving, but still provides services. I have three networks total, my standard 2.4GHz network, a 5GHz network and my Guest Network. To have bridged mode work as well as possible, you need to setup the same network on both AirPort Extremes, so that is what I setup.
At first I figured it might have been a temporary Comcast issue. I hardly ever need to go to the usps.com website, but there were a couple of packages that I wanted to track, and having to turn off wifi to do any tracking, while not the end of the world, was quite inconvenient.
I did the first set of maintenance that one does, I rebooted the cable modem as well as the 5th Generation AirPort Extreme. This did not fix anything, So the next step was to contact Comcast.
I contacted Comcast, and since it worked when directly connected via cable modem, there was not much else that they were able to do. As with most of their other things to test, they asked me to directly connect to the cable modem. When I connected directly to the cable modem, everything worked, so that clinched that it was something on my network.
I began doing some google searching, as one does, and I came across this thread on the Apple Discussion Forums.
I tried a couple of the things that they suggested in the thread. One of the suggestions was to make sure that “Enable NAT Port Mapping Protocol” was enabled. That was already checked, so that was not the issue. Another suggestion was to disable the Guest Network. When I did this, it fixed the issue. While this worked, something told me that this was not the issue.
I did some more testing. I remembered that I had not yet rebooted my 6th Generation AirPort Extreme, so I rebooted this and there was no change. I switched the network names on the 6th Generation AirPort Extreme. When I did this everything worked fine. Yet, this is not how it is supposed to work. When I switched the names back to the original names, the original behavior returned.
Since I was back to square one, this is when I decided to use an suggestion from the Apple Discussion thread and decided to disable the Guest Network on the 6th Generation AirPort Extreme. After I disabled everything worked. I left the guest network disabled for 30 minutes, and re-enabled it again. When I double-checked everything, it continued to work.
I cannot explain what caused the contention between the two guest networks, but leaving one of them disabled seemed to fix the issue. I do not know if this is due to clearing out some cache, or some other issue. If that had not worked, my next step would have been to downgrade the firmware to the previous version and see if that fixed the issue.
I will admit that my network configuration is a non-standard one, but it seems to me that the two AirPort Extremes should be able to handle the communications without any issues. However, given the number of wireless networks in my area, it could easily be that they all got confused and needed to be reset. One of the suggestions from the Apple Discussions thread was that it could be an issue with ISP caching. Ultimately, this may still be the case, and it could just be that it is temporarily working and may stop working again in the future.
One of the things I also opted to do was to enable IPv6. When I did this, I noticed a horrendous slowdown in internet connectivity. After having it enabled for a couple of days, I ended up turning it off. The speed decreases were just too much to handle.
The thing to keep in mind is that no matter how good technology gets, it is still bound to have problems every once in a while.