isc-dhcpd6 is stop responding after restart. root@client:~ # cat /etc/rc.conf hostname="client" keymap="pl.kbd" dumpdev="AUTO" sendmail_enable="NONE" sshd_enable="YES" ifconfig_em0_ipv6="inet6 fe80::2 prefixlen 64" ifconfig_em0_alias0="inet6 fdd0::2 prefixlen 64" ifconfig_em0_alias1="inet 192.168.10.102 netmask 255.255.255.0" root@server:~ # cat /etc/rc.conf hostname="server" keymap="pl.kbd" dumpdev="AUTO" sendmail_enable="NONE" sshd_enable="YES" dhcpd6_enable="YES" ifconfig_em0_ipv6="inet6 fe80::1 prefixlen 64" ifconfig_em0_alias0="inet6 fdd0::1 prefixlen 64" ifconfig_em0_alias1="inet 192.168.10.101 netmask 255.255.255.0" root@server:~ # cat /usr/local/etc/dhcpd6.conf authoritative; option dhcp6.preference 255; option dhcp6.info-refresh-time 900; option dhcp6.domain-search "lan"; subnet6 fdd0::/64 { option dhcp6.name-servers 2620:fe::fe; } root@server:~ # service isc-dhcpd6 start Starting dhcpd6. Internet Systems Consortium DHCP Server 4.4.2 Copyright 2004-2020 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Config file: /usr/local/etc/dhcpd6.conf Database file: /var/db/dhcpd6/dhcpd6.leases PID file: /var/run/dhcpd6/dhcpd6.pid Wrote 0 NA, 0 TA, 0 PD leases to lease file. Bound to *:547 Listening on Socket/6/em0/fdd0::/64 Sending on Socket/6/em0/fdd0::/64 root@server:~ # tcpdump -nvi em0 'port 547' tcpdump: listening on em0, link-type EN10MB (Ethernet), capture size 262144 bytes 14:15:01.510461 IP6 (hlim 1, next-header UDP (17) payload length: 36) fe80::2.546 > ff02::1:2.547: [udp sum ok] dhcp6 inf-req (xid=a4affe (client-ID hwaddr/time type 1 time 673096487 000c291ef735) (elapsed-time 0)) 14:15:01.512179 IP6 (hlim 64, next-header UDP (17) payload length: 53) fe80::1.547 > fe80::2.546: [udp sum ok] dhcp6 reply (xid=a4affe (client-ID hwaddr/time type 1 time 673096487 000c291ef735) (server-ID hwaddr/time type 1 time 673091986 000c29eb3fcf) (preference 255)) ^C 2 packets captured 51 packets received by filter 0 packets dropped by kernel root@client:~ # /usr/local/sbin/dhclient -S -v em0 Internet Systems Consortium DHCP Client 4.4.2 Copyright 2004-2020 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Listening on Socket/em0 Sending on Socket/em0 PRC: Requesting information (INIT). XMT: Forming Info-Request, 0 ms elapsed. XMT: Info-Request on em0, interval 1020ms. RCV: Reply message on em0 from fe80::1. PRC: Done. root@server:~ # service isc-dhcpd6 restart Stopping dhcpd6. Starting dhcpd6. Internet Systems Consortium DHCP Server 4.4.2 Copyright 2004-2020 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Config file: /usr/local/etc/dhcpd6.conf Database file: /var/db/dhcpd6/dhcpd6.leases PID file: /var/run/dhcpd6/dhcpd6.pid Wrote 0 NA, 0 TA, 0 PD leases to lease file. Bound to *:547 Listening on Socket/6/em0/fdd0::/64 Sending on Socket/6/em0/fdd0::/64 root@server:~ # tcpdump -nvi em0 'port 547' tcpdump: listening on em0, link-type EN10MB (Ethernet), capture size 262144 bytes 14:17:08.687100 IP6 (hlim 1, next-header UDP (17) payload length: 36) fe80::2.546 > ff02::1:2.547: [udp sum ok] dhcp6 inf-req (xid=a4affe (client-ID hwaddr/time type 1 time 673096487 000c291ef735) (elapsed-time 0)) 14:17:09.727073 IP6 (hlim 1, next-header UDP (17) payload length: 36) fe80::2.546 > ff02::1:2.547: [udp sum ok] dhcp6 inf-req (xid=a4affe (client-ID hwaddr/time type 1 time 673096487 000c291ef735) (elapsed-time 103)) 14:17:11.717431 IP6 (hlim 1, next-header UDP (17) payload length: 36) fe80::2.546 > ff02::1:2.547: [udp sum ok] dhcp6 inf-req (xid=a4affe (client-ID hwaddr/time type 1 time 673096487 000c291ef735) (elapsed-time 303)) 14:17:15.516819 IP6 (hlim 1, next-header UDP (17) payload length: 36) fe80::2.546 > ff02::1:2.547: [udp sum ok] dhcp6 inf-req (xid=a4affe (client-ID hwaddr/time type 1 time 673096487 000c291ef735) (elapsed-time 682)) 14:17:23.217165 IP6 (hlim 1, next-header UDP (17) payload length: 36) fe80::2.546 > ff02::1:2.547: [udp sum ok] dhcp6 inf-req (xid=a4affe (client-ID hwaddr/time type 1 time 673096487 000c291ef735) (elapsed-time 1453)) ^C 5 packets captured 45 packets received by filter 0 packets dropped by kernel root@client:~ # /usr/local/sbin/dhclient -S -v em0 Internet Systems Consortium DHCP Client 4.4.2 Copyright 2004-2020 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Listening on Socket/em0 Sending on Socket/em0 PRC: Requesting information (INIT). XMT: Forming Info-Request, 0 ms elapsed. XMT: Info-Request on em0, interval 1020ms. XMT: Forming Info-Request, 1030 ms elapsed. XMT: Info-Request on em0, interval 1950ms. XMT: Forming Info-Request, 3030 ms elapsed. XMT: Info-Request on em0, interval 3770ms. XMT: Forming Info-Request, 6820 ms elapsed. XMT: Info-Request on em0, interval 7610ms. XMT: Forming Info-Request, 14530 ms elapsed. XMT: Info-Request on em0, interval 15150ms. ^C