Yealink SIP-T2 SERIES Administrator's Manual page 782

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
Pri.DNS
network.ipv6_secondary_dns
Description:
Configures the secondary IPv6 DNS server.
Example:
network.ipv6_secondary_dns = 2026:1234:1:1:c3c7:c11c:5447:23a6
Note: It works only if the value of the parameter "network.ip_address_mode" is set
to 1 (IPv6) or 2 (IPv4 & IPv6). In DHCP environment, you also need to make sure the
value of the parameter "network.ipv6_static_dns_enable" is set to 1 (On). If you
change this parameter, the IP phone will reboot to make the change take effect.
Web User Interface:
Network->Basic->IPv6 Config->Static IP Address->Secondary DNS
Phone User Interface:
Menu->Settings->Advanced Settings (default password: admin)
->Network->WAN Port->IPv6->Static IPv6 Client->IPv6 Sec.DNS
Or Menu->Settings->Advanced Settings (default password: admin)
->Network->WAN Port->IPv6->DHCP IPv6 Client->Staic DNS(Enabled) ->IPv6
Sec.DNS
network.ipv6_icmp_v6.enable
Description:
Enables or disables the IP phone to obtain IPv6 network settings via SLAAC
(Stateless Address Autoconfiguration) method.
0-Disabled
1-Enabled
Note: If you change this parameter, the IP phone will reboot to make the change
take effect. It is only applicable to SIP VP-T49G/SIP-T48G/T46G/T29G IP phones.
SLAAC is enabled on SIP-T42G/T41P/T40P/T27P/T23P/T23G/T21(P) E2/T19(P) E2/CP860
IP phones by default. You are not allowed to configure this parameter for those IP
phones.
Web User Interface:
Network->Advanced->ICMPv6 Status->Active
Phone User Interface:
None
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Parameters Permitted Values
IPv6 address
0 or 1
Default
Blank
1