89
votes
Do you need separate IPv4 and IPv6 listen directives in nginx?
If you host multiple vhost domains with a single Nginx instance, you can't use the single combined listen directive
listen [::]:80 ipv6only=off;
for each of them. Nginx has a weird quirk where you ...
- 2,395
76
votes
Accepted
56
votes
Why does IPv6 use AAAA to represent its DNS records?
I take it this is a question specifically about the name of the RR type?
It obviously could have had a different name, the name AAAA for IPv6 address records is in reference to an IPv6 address (128 ...
- 34.4k
41
votes
sendmail can not deliver to gmail - IPv6 sending guidelines regarding PTR records not met
Check the current protocols:
postconf inet_protocols
net_protocols = all
Edit cf File if it returns all
grep 'inet_protocols' /etc/postfix/main.cf
inet_protocols = ipv4
Restart
service postfix ...
- 614
38
votes
Accepted
IPv6 subnetting a /64 - what will break, and how to work around it?
If the ISP won't give you more than a /64, then that ISP sucks. If it is any relief I can tell you that I have to deal with ISPs that suck even more than that. Around here it is perfectly normal to ...
- 30.2k
38
votes
Should my website have an IPv6 address?
Lack of IPv6 support on your site will hurt some of your users.
According to stats published by Google 20-25% of users currently have IPv6. A large fraction of those users will need to go through ...
- 30.2k
37
votes
Multiple devices with one IPv6 to the Internet?
IPv6 is designed to not do that. Trying IPv4 style NAT with IPv6 will break things. That said, I'm pretty sure you can do NAT IPv6 with Linux iptables, so it's not impossible. But I would strongly ...
- 7,672
34
votes
Accepted
How discoverable are IPv6 addresses and AAAA names by potential attackers?
Malicious bots don't guess IPv4 addresses anymore. They simply try them all. On modern systems this can take as little as a few hours.
With IPv6, this is not really possible any longer, as you've ...
- 241k
32
votes
Accepted
Why is IPv6 adoption higher at weekends?
tl;dr: Because Comcast.
Comcast has, by any measure, the largest IPv6 deployment in the world, with the greatest number of users. Commercial/business networks are lagging behind with regards to IPv6. ...
- 109k
30
votes
Accepted
Difference between 0.0.0.0/0 and ::/0 in access control lists
0.0.0.0/0 is the IPv4 everything - all possible IPv4 addresses.
::/0 is the IPv6 equivalent of that.
You can, for example, allow IPv4 and disallow IPv6 or vice versa.
@kasperd mentions:
It should ...
- 822
29
votes
Accepted
Are people really going to use public IPv6 addresses on their private networks?
Is that how IPv6 is intended to work?
In short, yes. One of the primary reasons for increasing the address space so drastically with IPv6 is to get rid of band-aid technologies like NAT and make ...
- 16.7k
27
votes
Accepted
Is an IPv6-only MTA possible yet?
Short answer: it will work, technically, but you will have lots of undeliverable mail.
Long answer: Take your SMTP logs. Sed out all the domain names you send mail to. Check if they have IPv6 DNS and ...
- 3,527
25
votes
Do Araknis switches support IPv6?
A switch doesn't know about IP.
Switches forward Ethernet frames. They don't need to know anything about the protocols at higher layers.
If it is a managed switch it may have a web interface used to ...
- 30.2k
23
votes
Prefer IPv4 incoming connections over IPv6
IPv6/IPv4 preference is determined by the initiator of a connection, i.e. the web browser. The address selection rules are defined in RFC 6724. While these can be overridden, it is only by the user ...
- 241k
23
votes
How to check IPv6 address via command line?
to show the localy listed ipv6 address one can use
ip -6 addr
This will show all locally configured ipv6 address including the link-local address. to show just global reachable addresses you can use
...
- 361
22
votes
Is an IPv6-only MTA possible yet?
The answer depends on your success criteria. But most likely will be no.
If you are running a business where any undelivered mail means a measurable cost. Then the answer is no, IPv6-only is not ...
- 30.2k
22
votes
Accepted
Is it safe to disable IPv6 on my Debian server?
No, do not disable IPv6. It breaks things, turns users without v4 away, and makes more work for your future project to use IPv6.
A host with only IPv4 addresses and routes will serve web sites just ...
- 31k
21
votes
IPv6: differences between "routed prefix" and "link prefix"?
The easiest way to understand the difference between the two is via an example showing the hierarchical nature of the prefixes.
An example hierarchy
An ISP has been allocated a prefix from a RIR (...
- 30.2k
21
votes
Accepted
sendmail can not deliver to gmail - IPv6 sending guidelines regarding PTR records not met
From Google's point of view, they are trying to verify the identity of the IP address connecting to them, so they will attempt to look up the PTR record for 2a01:4f8:212:27c8::2.
When they resolve ...
- 9,475
21
votes
Accepted
HTTPD listening in IPv6, according netstat, but reacheable in IPv4
I believe that on Linux, binding to [::] (IPv6) results in receiving both IPv6 and IPv4 traffic (by default). I believe these are referred to as IPv4-mapped IPv6 addresses. netstat simply shows the ...
- 9,271
21
votes
Are people really going to use public IPv6 addresses on their private networks?
We use public IPv6 addresses in our company network for all devices.
We use a stateful firewall on our gateway, that:
allows all icmpv6
allows new connections from internal network out
allows ...
- 1,573
21
votes
Multiple devices with one IPv6 to the Internet?
IPv6 doesn't have a NAT standard the way IPv4 does. There is an EXPERIMENMTAL RFC for one-to-one NAT (one outside address for each inside address) on IPv6, but explicitly forbids what you want to do (...
- 3,213
20
votes
Accepted
Why do you need IPv6 Neighbor Solicitation to get the MAC address?
Every node automatically generates a link-local address, but:
That address might not be generated with the EUI-64 format specified in RFC 2464. IPv6 addresses may also be cryptographically generated ...
- 241k
19
votes
Accepted
Can clients learn their time zone on a network configured using RA?
Stateless address autoconfiguration doesn't provide any way to transmit time zone information, but DHCPv6 does. The DHCPv4 options 100 and 101 correspond to the DHCPv6 options 41 and 42 respectively. ...
- 241k
19
votes
Accepted
NGINX SSL does not respond over IPv6
You have an MTU problem.
I tested wget -O /dev/null https://www.ekasparova.eu while observing the traffic with tcpdump. This is what I saw:
19:56:57.048361 IP6 2001:db8::1.47386 > 2a04:f310:100:3:...
- 30.2k
18
votes
What is the ipv6 equivalent of 0.0.0.0/0
::/0 is the short-form, but you could also write out all the zeros if you want.
0000:0000:0000:0000:0000:0000:0000:0000/0
- 34.4k
17
votes
Accepted
IPv4 To IPv6 Migration Advice
This seemed like overkill to me, we already wont come close to filling
the single /64 but this might be my IPv4 mindset confusing me.
Stop counting hosts, that's IPv4 thinking. Subnets come in one ...
- 31k
16
votes
(network unreachable) error in my server logs
It may be worth noting that in Debian Jessie with systemd, the -4 option in /etc/default/bind9 may be ignored. See bug #767798.
In that case, you need to modify the systemd bind9.service file:
Move ...
- 3,727
16
votes
Accepted
IPv6 support or alternative for aws vpc instances
Unfortunately AWS has been severely neglecting meaningful IPv6 support. Their "solution", if you can call it that, is to throw a non-VPC ELB in front of your application. For many reasons that is a ...
- 109k
15
votes
Prefer IPv4 incoming connections over IPv6
Such preferences can be expressed using SRV records. Unfortunately those are not supported for HTTP. So you are left with a situation where the client alone is making the choice between IPv4 and IPv6.
...
- 30.2k
Only top scored, non community-wiki answers of a minimum length are eligible