
  What would let a private IP address get routed across servers?


Let's define what a private IP address is first: It's an address that, by convention, is agreed to not be routed on the Internet. That means that we agree as a community to never advertise those routes over BGP. It also means that that an ISP will probably kill those routes at the borders to their network to prevent them from possibly propagating.

That doesn't mean, however, that a private IP can't cross routers. It is very possible and even highly likely that Comcast uses private IP address ranges for networking equipment that isn't ever supposed to communicate with the Internet as a whole. Those routes may be forwarded by interior routing protocols throughout the entire Comcast network.

All in all, I'm going to guess that it's the case that your router performs NAT translation and then default-routes all traffic that isn't local to the next hop router, including private IP space. It's not very likely, though, that there are many Comcast routers sporting default routes that accidentally go all the way to a responding host with a private IP. It's my strong assumption that this is something purposeful. It might be a temperature sensor with remote monitoring or some other equally innocuous device that never needs to be talked to by anybody outside of Comcast.


  Would the fact that it's all Comcast mean that they have their routers setup wrong?


Since your traceroute shows that all the packets remain within the Comcast network, it's actually not a very surprising circumstance that you've run into. It's staying within a single autonomous system and not violating any standards.

Private IP getting routed over Internet
We have a list of complicated things, which the user can click on to get a new view in which they can edit all the details stored for that thing.

The edit view already has a Cancel exit mechanism (default for all our edit forms) and it has a save button (which both saves and exits back to the list).

Should the Save button be disabled until changes are made to any of the details?
