IPv6 Native with Telstra, Australia

[randomaustralian]

Could this have to do with why there are weirdsettings about allowing local only communication?

pfSense reports that my wan_dhcp6 is a local IPv6 address even though i have internet rout-able addresses on my interfaces and my local network.

maybe Telstra are using local local link addresses on their internal network to distribute internet addresses? would that not be a thing?

[JKnott]

@randomaustralian said in IPv6 Native with Telstra, Australia:

maybe Telstra are using local local link addresses on their internal network to distribute internet addresses? would that not be a thing?

That's entirely normal with IPv6. Routing is usually done with link local addresses. If there's a routeable address on an interface, it's only there for testing, management, etc. It plays no part in routing.

Here's what mine shows:

Internet6:
Destination Gateway Flags Netif Expire
default fe80::217:10ff:fe9 UG re0

[Bigmaccius]

@randomaustralian as @JKnott has already stated it is normal to have a gateway that is a link-local address (i.e. fe80::). Thought it might be worth explaining this a little more in-depth. Also, what did you mean by "weird settings about allowing local only communication"?

Every IPv6 interface must have a link-local address (it is a stated requirement in RFC4291), and it is usually derived from the MAC address of the interface (as per RFC4862). For example, a MAC of 11:22:33:44:55:66 will have a link-local address of fe80::1122:33ff:fe44:5566 - here's a nice site that explains it. Also these addresses can be randomised (but must be unique within the same segment/broadcast domain), and you might see this in pfSense on the LAN interface when it gets an address fe80::1:1 being assigned as a link-local address; this is a nice way of being able to refer to the main router/gateway on the LAN and is easy to remember!

Having fe80::1:1 for your router on a LAN is useful also because what if you needed to replace your pfSense hardware? The new hardware would have a different MAC and hence a different default link-local address (i.e. imagine restoring your config to a new firewall). Just makes it easier and less disruptive to a network that might contain a lot of active hosts trying to route their traffic out through a link-local that has disappeared.

Back to your gateway example screenshots. What's happening here is that your gateway points to the fe80:: (link-local) address of your ISP's router and pfSense will be forwarding outbound IPv6 packets to that address - those packets will contain the source and dest IPv6 addresses that are publicly routable.

If you flip this around and think about what your ISP is doing to send IPv6 packets to your pfSense firewall - they will either be forwarding them to your WAN's fe80:: (link-local) address or may be sending them to the pfSense WAN's publicly routable (i.e. 2001:8003:f00...) address - it could be either, I'm not exactly sure which is more common - if your WAN doesn't have a public IPv6 address (which is possible if it never requested an IA_NA and only an IA_PD) then your ISP would be routing to your WAN's fe80:: (link-local) address since it would have no other choice.

If you want further reading on this I did find an RFC7404 that discusses using link-local addresses inside IPv6 networks for links between routers and the advantages and disadvantages. From what I have seen so far in IPv6 networks there's no single answer that is right, and network engineers will often have very strong opinions about how one approach is right and vice-versa. I like to subscribe to the simple rule: if it's working don't touch it!

[JKnott]

@bigmaccius said in IPv6 Native with Telstra, Australia:

they will either be forwarding them to your WAN's fe80:: (link-local) address or may be sending them to the pfSense WAN's publicly routable (i.e. 2001:8003:f00...) address - it could be either, I'm not exactly sure which is more common

Both resolve to the same MAC address, which is what is used to send frames over Ethernet or other layer 2. All a router needs to know is which interface to use. In fact, on point to point links there's not even a need for any IP address. Using either IPv6 address can be used to obtain the MAC address for forwarding, but my understanding is that it's usually the link local. As you mentioned, it's always going to be available.

Incidentally, I've been through this sort of thing, trying to explain a problem to my ISP. While I get a prefix on my LAN, it's not usable, as there is no correct route back to my network. If I, for example ping www.yahoo.com, I can see the pings go out, but nothing comes back. However, pinging from the firewall, rather than a computer behind it works. One guy Iwas speaking to insisted that proved IPv6 was working properly, although in fact it wasn't. It's real "fun" trying to explain to the support people how IPv6 actually works.

[biggsy]

Just wanted to say thanks to all involved with finding a solution to this. Excellent work.

It looks like I'll be getting NBN/HFC some time between April and June (this year, they say).

Having this IPv6 configuration information in advance will be a huge help. Unless Telstra change their end, of course.

[Larrikin]

@biggsy said in IPv6 Native with Telstra, Australia:

Having this IPv6 configuration information in advance will be a huge help. Unless Telstra change their end, of course.

We will keep up with them, so no need to worry. I've already been in contact with my Telstra contact this morning. All good.

[Larrikin]

@bigmaccius @Derelict

Check out how much traffic is flowing on IPv6 since I switched it on:

[randomaustralian]

@larrikin

not so much here. but i am only a single user

[randomaustralian]

@jknott and @Bigmaccius

"Telstra are using local local link addresses....."

Thanks for the clarification. this is my first successful experience with IPv6 so its been an interesting learning curve. Always more stuff to learn.

and by "weird settings about allowing local only communication"....

i must have gotten confused with one of the other forums i was reading. something about forcing ipv6 to allow local only communication to work on telstra.

[Larrikin]

@randomaustralian @Bigmaccius @Derelict

I notice that with IPv6 enabled, that my download and upload speeds on IPv4 reduce by about 1.5Mb/s (megabits). When I disable IPv6, my IPv4 speeds are fully restored. Any idea why that would occur? @randomaustralian @Bigmaccius have either of you noticed this?

I checked my CPU (which is absolutely massive for my firewall - intel i7 4660K) and it runs at 1% CPU at the best of times :), so its not a CPU issue.

I don't get this issue with the Telstra router - just with PFSense.

[Gertjan]

IPv6 Packet "Background noise" ?

[Larrikin]

@gertjan said in IPv6 Native with Telstra, Australia:

IPv6 Packet "Background noise" ?

I monitor my WAN interface using SNMP and there is no background traffic going on.

[Larrikin]

This post is deleted!

[Gertjan]

@larrikin said in IPv6 Native with Telstra, Australia:

I monitor my WAN interface using SNMP and there is no background traffic going on.

On my very small company network (30 devices) I can't follow the pace of this one :

tcpdump -i eth0 -vv ip6

where eth0 is my IPv6 WAN interface.
A 1 KB / sec flux.

try also

systat -ifstat

I've got a solution for you !

(ok, silly joke)

[Larrikin]

@gertjan Have you got a mac computer? download peakhourapp.com and point that to your firewall :). Much easier than the above. It tells you exactly the speeds of your interfaces in real time.

[Larrikin]

@Derelict I am certain I have come across some sort of bug in pfsense that when IPv6 is enabled, IPv4 performance decreases by about 2mb/s both up and down.

I have done lots of testing tonight and Telstra's router does not suffer this issue, only pfsense.

The moment I turn off IPv6, I get my full speeds back. The moment I turn on IPv6, I lose 2mb/s down and up on IPv4. I cannot replicate that on Telstra's router. I maintain full speeds on IPv4 with IPv6 enabled on Telstra's router.

What additional information would you need to help isolate what this bug would be?