Adding global IPv6 addresses using SLAAC

fl0cke asked:

Stateless Adress Autoconfiguration allows a node on the link to automatically configure global IPv6 addresses by appending its interface identifier (64 bits) to the prefix (64 bits) advertised by the router.

Lets assume I have a server with the global IPv6 Adress

2001:0db8:85a3:08d3:1319:8a2e:0370:7347

Now i want to add another global IPv6 address to the same interface by changing just the interface identifier and keeping the prefix. e.g.

2001:0db8:85a3:08d3:3315:2b5e:a320:3254
-------same--------|-----different-----                                

How can i do that using SLAAC, where the interface identifier is automatically appended to the network prefix? I am currently using Ubuntu.

(This is similar to what the IPv6 Privacy Extension does, but i want to control adding and removing temporary IPv6 addresses myself.)

My answer:


At the moment, I’m not aware of any method for manually causing the system to switch to a new temporary address.

However, you can tune the time period in which a temporary address is used and cause the system to create them more frequently.

From the kernel documentation:

temp_valid_lft - INTEGER
    valid lifetime (in seconds) for temporary addresses.
    Default: 604800 (7 days)

temp_prefered_lft - INTEGER
    Preferred lifetime (in seconds) for temporary addresses.
    Default: 86400 (1 day)

(Yes, the misspelling is intentional…)

So, let us say you want the system to start using a new temporary address every 10 minutes. You will then set:

sysctl net.ipv6.conf.all.temp_prefered_lft=600
sysctl net.ipv6.conf.default.temp_prefered_lft=600

The other sysctl, temp_valid_lft, allows some extra time for existing connections using a temporary address to finish up. You can also reduce this, especially if you don’t anticipate long running connections. Here I reduce it to 1 hour:

sysctl net.ipv6.conf.all.temp_valid_lft=3600
sysctl net.ipv6.conf.default.temp_valid_lft=3600

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