[CentOS] Howto install Centos6/7 Comcast WA/OR

[Richer, Mark (CIV)]

David,

I can’t comment on Comcast’s IPv6 deployment in OR and WA, but I have set up IPv6 so I can address some general issues FWIW.

You don’t need to enable IPv6 just because it’s available. I don’t know why one would, on the other hand, consider disabling IPv4 unless you only want to communicate with other IPv6 systems which is very limiting.  However, you can configure IPv6 independently of IPv4 and do it any time you want without having to start from scratch. Generally you don’t need to reboot  even to change your network configuration so you can modify any existing system as far as I know. I mostly edit/write network-scripts to configure the interfaces. I use the GUI tools sometimes but often find they are limiting.

You don’t need to use DHCP6 with IPv6 to assign addresses — at least not generally speaking, though I can’t speak to the specifics of Comcast and the DCP3939 Router configuration. In general, IPv6 hosts can auto-configure without using a DHCP6 server. I couldn’t think of a good reason to use one because it’s not needed to assign addresses dynamically. I guess there must be reasons some folks use one. Regardless, you can assign manual IPv6 addresses and optionally add them to your zone files.

If you need to test IPv6 configurations when you are connected to an IPv4-only network, you can get a free IPv6 tunnel account from Hurricane Electric:

https://tunnelbroker.net

At home in Virginia, I have Comcast, and use the tunnel to test the IPv6 configuration at our office.

By default, IPv6 addresses route externally, but you can assign local private IPv6 addresses.  I have only configured addresses that do route externally and these don't need to do any forwarding to use port 22 (though you need to make sure your IPv6 firewall rules allow access.). For example I can ssh directly to an IPv6 address using my tunnel at home.

Hope that helps a bit.

Mark

MARK H RICHER, MS CS
NPS-NCR Digital Forensics Lab IT Manager
Computer Science Department
Naval Postgraduate School - National Capital Region (NCR)
900 N Glebe Rd, Rm 5-182, Arlington, VA 22203
571.858.3254 (o) 571.303.9498 (m) mhricher at nps.edu<mailto:mhricher at nps.edu>

On Dec 13, 2014, at 11:36 AM, david <david at daku.org<mailto:david at daku.org>> wrote:

Has anyone managed to install a Centos6 or Centos7 in Washington or Orgegon, or anywhere else that Comcast has deployed the IPV6to4 routers.  The router in question is a Xfinity DCP3939 Router with Wireless, and I'm trying to get a Centos system working behind that router (with a wired connection), and enable SSH access from outside.

Does one have to enable both IPV6 and IPV4?
Can I enable IPV6 after install, or do I have to restart the installation from scratch (it has Centos6 installed via an earlier IPV4 router).

How does one configure the router so that its DHCP system awards a known address to that machine, and how to forward port 22?

The extra problem is that I'm trying to advise the owner of this configuration remotely.  Behind that same router he has a working Windows 7 machine, and I can use Team Viewer to view the router's configuration from "inside".

Any assistance would be appreciated.  Comcast is of no help.

David



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