I have a corner-case where I need to leave the
family inet6 configuration under IFL present while hosts in that network should not use IPv6. This means, that the logical interface of a router will contain a family inet6 and a link-local address:
root@r1> show interfaces ge-0/0/0.10 Logical interface ge-0/0/0.10 (Index 332) (SNMP ifIndex 534) Flags: Up SNMP-Traps 0x4000 VLAN-Tag [ 0x8100.10 ] Encapsulation: ENET2 Input packets : 0 Output packets: 146 Protocol inet6, MTU: 1500 Max nh cache: 75000, New hold nh limit: 75000, Curr nh cnt: 0, Curr new hold cnt: 0, NH drop cnt: 0 Addresses, Flags: Is-Preferred Destination: fe80::/64, Local: fe80::206:a00:a0e:fff0 Protocol multiservice, MTU: Unlimited root@r1>
This should mean, that when hosts manually configure global unicast address, then in theory, they can reach the destination, but the packet is not routed back to them. However, this is not even viable because of RPF check. Also, hosts can reach the router over IPv6, but I don't see this as a problem. Are there any other risks/disadvantages with this setup?