From Fedora Project Wiki
< Networking | Ideas
Current status
Features
- Automatic link-local addresses
- Manual addresses
- Automatic global address
- Gateway/DNS for other hosts (IPv4 only)
Feature dependencies
- IPv6: Automatic global address needs link-local address
- Gateway needs a manual address (at least a default one), conflicts with dynamic address
IPv4/IPv6 methods
| Method | Protocol | Link-local | Manual | Automatic | Gateway |
|---|---|---|---|---|---|
| disabled | IPv4 | none | forbidden | none | none |
| ignore | IPv6 | kernel | forbidden | kernel | none |
| link-local | IPv4 | userspace | forbidden | none | none |
| link-local | IPv6 | kernel | forbidden | none | none |
| manual | IPv4 | none | required | none | none |
| manual | IPv6 | kernel | required | none | none |
| auto | IPv4 | none | allowed | dhcp | none |
| auto | IPv6 | kernel | allowed | ra+dhcp | none |
| dhcp | IPv6 | kernel | allowed | dhcp | none |
| shared | IPv4 | none | ? | none | dhcp+dns+NAT |
Notes
- Even when IPv4 is in the disabled state, the network interface communicates on the L2 level.
- There's no disable method for IPv6 and its semantics is unclear (whether disable means the same as link-local, or it also applies to the link-local address which is unaffected in all other methods).
- The usage of IPv4 and IPv6 link-local addresses substatially differs. While IPv6 uses link-local addresses for *all* methods, IPv4 only uses it for the special link-local method.
- The IPv4 disable and IPv4/manual methods only differ in the number of addresses (0 versus >=1), therefore one of them is redundant.
- The IPv6 link-local and IPv6/manual methods only differ in the number of addresses (0 versus >=1), therefore one of them is redundant.
- The IPv6 dhcp method is currently defunct.
- There's no IPv6 shared method, yet.
Feature combinations
| L | M | A | G | IPv4 | IPv6 | notes |
|---|---|---|---|---|---|---|
| no | no | no | no | disabled | unsupported | kernel's disable_ipv6 buggy |
| no | no | no | yes | invalid | invalid | missing manual address |
| no | no | yes | no | auto | invalid | missing IPv6 link-local address |
| no | no | yes | yes | invalid | invalid | missing manual address |
| no | yes | no | no | manual | unsupported | missing kernel feature |
| no | yes | no | yes | shared | unsupported | missing kernel feature |
| no | yes | yes | no | auto | unsupported | missing kernel feature |
| no | yes | yes | yes | invalid | invalid | both sides of dynamic configuration |
| yes | no | no | no | link-local | link-local | |
| yes | no | no | yes | invalid | invalid | missing manual address |
| yes | no | yes | no | unsupported | auto | |
| yes | no | yes | yes | invalid | invalid | missing manual address |
| yes | yes | no | no | unsupported | manual | |
| yes | yes | no | yes | shared | unsupported | |
| yes | yes | yes | no | unsupported | auto | |
| yes | yes | yes | yes | invalid | invalid | both sides of dynamic configuration |
- L: Automatic link-local addresses
- M: Manual addresses
- A: Automatic global address
- G: Gateway/DNS for other hosts
Notes
- There's a bug in the kernel (found by Dan Winship) that once setting IFF_UP with disable_ipv6=1 affects future state. But we shouldn't need disable_ipv6 just as we don't need disable_ipv4, see the next note.
- Kernel doesn't support turning link-local addressing on/off (without affecting other features).
Proposal
Use one configuration directives per feature whenever possible, use multiple configuration directives per feature where further tweaking is needed.
| name | value | meaning |
|---|---|---|
| link-local | enabled | configure LL address as soon as possible |
| fallback | configure a LL address when other configuration methods failed | |
| disabled | default for IPv4 | |
| undefined | default for IPv6, use system default | |
| ra | enabled | default, IPv6 only |
| disabled | skip directly to DHCP (if enabled) | |
| dhcp | enabled | default |
| disabled | never use DHCP, only useful for IPv6 | |
| sharing | enabled | provide sharing facilities |
| disabled | default |