Why is giving multiple addresses a problem?

No control over which source address is used. I'm assigning a lot of clients DHCP reservations so I can use static addresses for monitoring and firewall rules. With multiple addresses on the same network, clients may use their SLAAC address which won't match the firewall rule.

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db48x a day ago | parent | next [-]

That still doesn’t really make sense. Why not run SLAAC on one subnet and have a single firewall rule for the whole thing? You’re not running any major servers on an Android phone, so it won’t be anything complex.

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tsimionescu a day ago | parent [-]

SLAAC can only run on a subnet that's larger than /64, which they might not have access to.

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db48x a day ago | parent [-]

Strictly speaking it can and does run on subnets that are exactly /64. Does anyone actually hand out smaller delegations today?

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tsimionescu a day ago | parent [-]

My point is that they might only be getting 1 /64 from their ISP; or getting a /62 or something small, and needing more subnets anyway. In these situations, you may not have an extra /64 to dedicate to SLAAC for certain devices.

	▲	db48x a day ago \| parent [-]
		Right. I was merely correcting your statement that SLAAC needs more than 64 bits to work with. But my question remains; do any ISPs hand out smaller delegations than a /64?

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justincormack 21 hours ago | parent | prev | next [-]

There are APIs in Linux to control source address selection but might be fiddly https://www.davidc.net/networking/ipv6-source-address-select...

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franklyworks a day ago | parent | prev [-]

Ah, this makes sense.