3 ms·

Is there any risks of nodes assigning same IP if there's no central DHCP?

screamingninja 4y ago
Unlike in IPv4, in IPv6 there is a lower risk of nodes assigning the same IPv6 address if there's no central DHCP. This is because IPv6 uses a unique interface identifier (IID) that is automatically generated by the node based on its MAC address and a random value. This makes it highly unlikely that two nodes on the same network would generate the same IID and therefore, the same IPv6 address.
- CaliforniaKarl 4y ago
  For some time now, it's not unusual for systems to have multiple, publicly-routable IPv6 IPs. Right now my macOS system has four randomly-generated IPv6 IPs, which are being used for internet traffic. New IPs are generated regularly, and old ones eventually get removed. And thanks to Duplicate Address Detection, before a new randomly-generated IP is used, a check is made to ensure it is not in use by someone else.
ilyt 4y ago
Not if you don't have same MAC in the network . SLAAC reserves bottom 64 bits for autoconfiguration, and while incredibly wasteful it does ensure every MAC can have its own IP address
riobard 4y ago
Don't worry coz DAD (Duplicate Address Detection) will come to your rescue :p
teddyh 4y ago
Firstly, normally nodes base their automatic IPv6 address on their MAC address, so there will be no conflict between these, since MAC addresses are supposed to be unique to the hardware. Otherwise, it’s a random 64-bit number (actually a few less bits, but not many). It’s very unlikely a collision will happen. And even if it does, there is a protocol (Duplicate Address Detection) to detect it, and avoid it.
- CaliforniaKarl 4y ago
  The current state has those two items flipped: Randomly-generated IPs is normal, and MAC-based IPs is the exception. https://www.internetsociety.org/resources/deploy360/2014/privacy-extensions-for-ipv6-slaac/ https://www.internetsociety.org/resources/deploy360/2014/pri...
  - teddyh 4y ago
    Right, thank you for the update. Personally, I don’t feel the need for privacy at this level of the protocol stack, and if I did, I would not consider IPv6 Privacy Extensions to be adequate. Also, I might like to keep TCP connections alive for more than a day. Therefore, I personally prefer regular MAC-based SLAAC, or even hard-coded addresses, over randomized and rotating addresses.
p1mrx 4y ago
You can generate sqrt(2^64) random suffixes before the probability of collision becomes significant. That number is in the billions for a single /64 network. In other words, no.

Unlike in IPv4, in IPv6 there is a lower risk of nodes assigning the same IPv6 address if there's no central DHCP. This is because IPv6 uses a unique interface identifier (IID) that is automatically generated by the node based on its MAC address and a random value. This makes it highly unlikely that two nodes on the same network would generate the same IID and therefore, the same IPv6 address.

CaliforniaKarl 4y ago
For some time now, it's not unusual for systems to have multiple, publicly-routable IPv6 IPs. Right now my macOS system has four randomly-generated IPv6 IPs, which are being used for internet traffic. New IPs are generated regularly, and old ones eventually get removed. And thanks to Duplicate Address Detection, before a new randomly-generated IP is used, a check is made to ensure it is not in use by someone else.

ilyt 4y ago

Not if you don't have same MAC in the network . SLAAC reserves bottom 64 bits for autoconfiguration, and while incredibly wasteful it does ensure every MAC can have its own IP address

riobard 4y ago

Don't worry coz DAD (Duplicate Address Detection) will come to your rescue :p

teddyh 4y ago

Firstly, normally nodes base their automatic IPv6 address on their MAC address, so there will be no conflict between these, since MAC addresses are supposed to be unique to the hardware. Otherwise, it’s a random 64-bit number (actually a few less bits, but not many). It’s very unlikely a collision will happen. And even if it does, there is a protocol (Duplicate Address Detection) to detect it, and avoid it.

CaliforniaKarl 4y ago
The current state has those two items flipped: Randomly-generated IPs is normal, and MAC-based IPs is the exception. https://www.internetsociety.org/resources/deploy360/2014/privacy-extensions-for-ipv6-slaac/ https://www.internetsociety.org/resources/deploy360/2014/pri...
- teddyh 4y ago
  Right, thank you for the update. Personally, I don’t feel the need for privacy at this level of the protocol stack, and if I did, I would not consider IPv6 Privacy Extensions to be adequate. Also, I might like to keep TCP connections alive for more than a day. Therefore, I personally prefer regular MAC-based SLAAC, or even hard-coded addresses, over randomized and rotating addresses.

p1mrx 4y ago

You can generate sqrt(2^64) random suffixes before the probability of collision becomes significant. That number is in the billions for a single /64 network. In other words, no.