The following object-group consists the latest IANA ROOT DNS Servers which can be used on the Cisco ASA firewalls.
IANA Root DNS Servers (IPv4/IPv6)
object-group network IANA-ROOT-DNS
description IANA Root DNS Servers (IPv4/IPv6)
network-object host 198.41.0.4
network-object host 2001:503:ba3e::2:30
network-object host 192.228.79.201
network-object host 2001:500:84::b
network-object host 192.33.4.12
network-object host 2001:500:2::c
network-object host 199.7.91.13
network-object host 2001:500:2d::d
network-object host 192.203.230.10
network-object host 192.5.5.241
network-object host 2001:500:2f::f
network-object host 192.112.36.4
network-object host 128.63.2.53
network-object host 2001:500:1::803f:235
network-object host 192.36.148.17
network-object host 2001:7fe::53
network-object host 192.58.128.30
network-object host 2001:503:c27::2:30
network-object host 193.0.14.129
network-object host 2001:7fd::1
network-object host 199.7.83.42
network-object host 2001:500:3::42
network-object host 202.12.27.33
network-object host 2001:dc3::35
Another method is to split the servers into IPv4 and IPv6 so if necessary you can call specific object-group on another ACL.
IPv4 Servers as follows…
IANA IPv4 Root DNS Servers
description IANA IPv4 Root DNS Servers
network-object host 198.41.0.4
network-object host 192.228.79.201
network-object host 192.33.4.12
network-object host 199.7.91.13
network-object host 192.203.230.10
network-object host 192.5.5.241
network-object host 192.112.36.4
network-object host 128.63.2.53
network-object host 192.36.148.17
network-object host 192.58.128.30
network-object host 193.0.14.129
network-object host 199.7.83.42
network-object host 202.12.27.33
IPv6 Servers as follows…
IANA IPv6 Root DNS Servers
object-group network IANA-IPv6-ROOT-DNS
description IANA IPv6 Root DNS Servers
network-object host 2001:503:ba3e::2:30
network-object host 2001:500:84::b
network-object host 2001:500:2::c
network-object host 2001:500:2d::d
network-object host 2001:500:2f::f
network-object host 2001:500:1::803f:235
network-object host 2001:7fe::53
network-object host 2001:503:c27::2:30
network-object host 2001:7fd::1
network-object host 2001:500:3::42
network-object host 2001:dc3::35
And combine both IPv4 and IPv6 into a group-object…
IANA IPv4 & IPv6 Root DNS Servers
object-group network IANA-ROOT-DNS
description IANA IPv4 & IPv6 Root DNS Servers
group-object IANA-IPv4-ROOT-DNS
group-object IANA-IPv6-ROOT-DNS