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Thanks, that helps a lot. This got me reading about IPv6 again. I'm trying to figure out how we'd set up an IPv6 network in the case where we have 1) Two upst

Thanks, that helps a lot. This got me reading about IPv6 again. I'm trying to figure out how we'd set up an IPv6 network in the case where we have 1) Two upstream ISPs, mostly for failover, but could be loadbalanced too. 2) Internal servers with assigned DNS My initial thoughts were that for each of the two ISPs, each host (e.g. personal desktop or laptop) would use the IPv6 prefix and end up with two addresses. But in the interest of having an internal address for internal servers, we'd need yet another IPv6 prefix for internal use. That makes 3 IPv6 addresses per host. Does that make sense? I read about getting Provider Independent (PI) address prefixes, which would allow use to consolidate to a single IPv6 prefix, but from what I read, that costs money and should generally be used for large organizations. Ugh.

Arnavion 4y ago
If you want failover-independent IPs you can keep using NAT, ie NPTv6, at the gateway level and not bother with giving public IPs to your LAN machines.
- GICodeWarrior 4y ago
  Have you implemented NPTv6 before? What routing product(s) have you implemented this with? Do you happen to have some documentation links handy? In my experience, this capability is missing from most off-the-shelf solutions, and in the cases where it is available, the documentation of this feature is missing or incomplete.
- justin_oaks 4y ago
  That's possible, but my understanding is that NPTv6 is strongly discouraged. Part of the point of IPv6 is do away with NAT and the problems caused by it. I was hoping there was a better way.
  - Arnavion 4y ago
    Yes, that is correct. But not having NAT is the same as having addresses that depend on the subnet prefix.
  - GICodeWarrior 4y ago
    NPTv6 is different from IPv4 NAT and doesn't really have the same issues. A different solution I've seen proposed for networks with multiple ISPs is to advertise both public prefixes to the network and let each client endpoint figure out which egress to use. This seems like a worse idea though. The most official approach is to get your own public IPv6 prefix and work with your ISPs to BGP route that to you on both links. However, home and small business ISPs generally don't offer this.
  - Dagger2 4y ago
    Use the GUA prefix from the main ISP. During failover, retract it and switch to the GUA prefix from the second ISP. Prefix translate any stragglers that don't switch to the new prefix for whatever reason. For active/active you can distribute both prefixes, but you don't get much control over which network clients pick. You can do the same thing here though: NAT only the outbound connections that you specifically want to steer onto the other ISP. This way you avoid most of the problems of NAT.
Bluecobra 4y ago
You don’t have to be a large corporation to have your own IP space. Getting your own IP space assigned by an authority like ARIN and getting a BGP AS number is the way to go here. I think ARIN allocates out IPv6 space out for free or low cost. There are yearly maintenance fees involved but should still be affordable for a small business. If this is for home use, then yeah that would be overkill.

Arnavion 4y ago

If you want failover-independent IPs you can keep using NAT, ie NPTv6, at the gateway level and not bother with giving public IPs to your LAN machines.

GICodeWarrior 4y ago
Have you implemented NPTv6 before? What routing product(s) have you implemented this with? Do you happen to have some documentation links handy? In my experience, this capability is missing from most off-the-shelf solutions, and in the cases where it is available, the documentation of this feature is missing or incomplete.
justin_oaks 4y ago
That's possible, but my understanding is that NPTv6 is strongly discouraged. Part of the point of IPv6 is do away with NAT and the problems caused by it. I was hoping there was a better way.
- Arnavion 4y ago
  Yes, that is correct. But not having NAT is the same as having addresses that depend on the subnet prefix.
- GICodeWarrior 4y ago
  NPTv6 is different from IPv4 NAT and doesn't really have the same issues. A different solution I've seen proposed for networks with multiple ISPs is to advertise both public prefixes to the network and let each client endpoint figure out which egress to use. This seems like a worse idea though. The most official approach is to get your own public IPv6 prefix and work with your ISPs to BGP route that to you on both links. However, home and small business ISPs generally don't offer this.
- Dagger2 4y ago
  Use the GUA prefix from the main ISP. During failover, retract it and switch to the GUA prefix from the second ISP. Prefix translate any stragglers that don't switch to the new prefix for whatever reason. For active/active you can distribute both prefixes, but you don't get much control over which network clients pick. You can do the same thing here though: NAT only the outbound connections that you specifically want to steer onto the other ISP. This way you avoid most of the problems of NAT.

Bluecobra 4y ago

You don’t have to be a large corporation to have your own IP space. Getting your own IP space assigned by an authority like ARIN and getting a BGP AS number is the way to go here. I think ARIN allocates out IPv6 space out for free or low cost. There are yearly maintenance fees involved but should still be affordable for a small business. If this is for home use, then yeah that would be overkill.