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Do you use uPnP? Do you do any port forwarding? If the answer to either of those questions is "Yes", then you should consider activating IPv6, if your ISP supp

Do you use uPnP? Do you do any port forwarding? If the answer to either of those questions is "Yes", then you should consider activating IPv6, if your ISP supports it.[0] The most tight-assed ISPs give you a /64 allocation. Because most machines use something called SLAAC, this means that this /64 is enough for a single subnet. The IETF strongly recommends that ISPs hand out at least a /56, but really wants to see /52s being handed out to each customer. In San Francisco, it seems that Comcast Residential connections get handed out at most a /60. Comcast uses DHCPv6-PD, so your DHCPv6 client needs to ask for the larger allocation. On routers that support IPv6, configuring your client to do this is typically very easy. As an aside, if you enable IPv6, please don't filter ICMP. ICMP was pretty important in IPv4, and has become absolutely critical in IPv6. [0] If you use uPnP, you're relying on firewalls on your endpoints for your security anyway -because any host can poke a hole in the NAT at any time-, so activating IPv6 doesn't substantially change your security situation.

zyx321 11y ago
>The IETF strongly recommends that ISPs hand out at least a /56 I never really understood that. IPv6 has 128 bit addresses, so even at /96 every single customer will have as many addresses as the entire IPv4 space. Why is /64 considered "tight-assed"?
- welterde 11y ago
  Right now SLAAC (Stateless address autoconfiguration) needs at least a /64 to work properly, thus only giving the customer a /64 means they can't run autoconfig on more than one broadcast segment.
hobarrera 11y ago
Why would they used DHCPv6 instead of SLAAC? It seems more complex, and I don't see any advantages. SLAAC is like the "default" for IPv6, while DHCP is something on top of it. Plus it's usually not enable out-of-the-box on all devices.
- simoncion 11y ago
  So, I'm speaking from a position of ignorance. My questions aren't rhetorical: they're me actually asking for more information. Also, some of my footnotes might contain information that you already know well. I apologize in advance. * How do you reliably send down DNS information with just router advertisements? [0] AIUI, and the last time I checked, Debian, Gentoo, and Ubuntu Linux, and Windows 7 and earlier versions of Windows all fail to add the contents of RDNSS advertisements to their list of DNS servers to be contacted. (You can configure Linux to put RDNSS info in /etc/resolv.conf, but -when I was testing-, none of the Linuxes I used were configured this way out of the box.) * I have my ISP-delegated /60 sliced up into a few subnets. If Comcast changes the prefix delegated to me, my subnet configuration is automatically maintained [1]. If an ISP uses only router advertisements to assign IPv6 prefixes, how can the ISP retain the ability to shuffle customer prefixes around while allowing the customer to automatically maintain his subnet layout in the face of such prefix changes? * Relatedly, is there routing software that you can configure to automatically slice -say- a /48 advertised from upstream via router advertisements into /64's that are then advertised on a LAN? To directly answer the question you posed: "I don't know why an ISP would pick DHCPv6-PD over SLAAC, but DHCPv6-PD does seem to solve some problems.". [0] I run my own DNS server, but others care about their ISP's DNS information. So, the answer to this question doesn't matter to the operation of my network, but the answer does interest me. [1] Assume that my ISP delegates to me 2001:1:1::/48. From that, I slice two networks: 2001:1:1:1::/64 and 2001:1:1:2::/64. I specify this by saying "Gimmy two networks from the /48 that I will be handed down to you. Number the first network $PREFIX:1::/64 and the second $PREFIX:2::/64." With my setup, my ISP can change the prefix it delegates to me to 2001:1:2::/48, and my network will automatically renumber itself. This is a bit of a pain for me, as I have to update DNS, but far less of a pain than having to update the configuration for the software that defines my subnets.

zyx321 11y ago

>The IETF strongly recommends that ISPs hand out at least a /56 I never really understood that. IPv6 has 128 bit addresses, so even at /96 every single customer will have as many addresses as the entire IPv4 space. Why is /64 considered "tight-assed"?

welterde 11y ago
Right now SLAAC (Stateless address autoconfiguration) needs at least a /64 to work properly, thus only giving the customer a /64 means they can't run autoconfig on more than one broadcast segment.

hobarrera 11y ago

Why would they used DHCPv6 instead of SLAAC? It seems more complex, and I don't see any advantages. SLAAC is like the "default" for IPv6, while DHCP is something on top of it. Plus it's usually not enable out-of-the-box on all devices.

simoncion 11y ago
So, I'm speaking from a position of ignorance. My questions aren't rhetorical: they're me actually asking for more information. Also, some of my footnotes might contain information that you already know well. I apologize in advance. * How do you reliably send down DNS information with just router advertisements? [0] AIUI, and the last time I checked, Debian, Gentoo, and Ubuntu Linux, and Windows 7 and earlier versions of Windows all fail to add the contents of RDNSS advertisements to their list of DNS servers to be contacted. (You can configure Linux to put RDNSS info in /etc/resolv.conf, but -when I was testing-, none of the Linuxes I used were configured this way out of the box.) * I have my ISP-delegated /60 sliced up into a few subnets. If Comcast changes the prefix delegated to me, my subnet configuration is automatically maintained [1]. If an ISP uses only router advertisements to assign IPv6 prefixes, how can the ISP retain the ability to shuffle customer prefixes around while allowing the customer to automatically maintain his subnet layout in the face of such prefix changes? * Relatedly, is there routing software that you can configure to automatically slice -say- a /48 advertised from upstream via router advertisements into /64's that are then advertised on a LAN? To directly answer the question you posed: "I don't know why an ISP would pick DHCPv6-PD over SLAAC, but DHCPv6-PD does seem to solve some problems.". [0] I run my own DNS server, but others care about their ISP's DNS information. So, the answer to this question doesn't matter to the operation of my network, but the answer does interest me. [1] Assume that my ISP delegates to me 2001:1:1::/48. From that, I slice two networks: 2001:1:1:1::/64 and 2001:1:1:2::/64. I specify this by saying "Gimmy two networks from the /48 that I will be handed down to you. Number the first network $PREFIX:1::/64 and the second $PREFIX:2::/64." With my setup, my ISP can change the prefix it delegates to me to 2001:1:2::/48, and my network will automatically renumber itself. This is a bit of a pain for me, as I have to update DNS, but far less of a pain than having to update the configuration for the software that defines my subnets.