HP 635n HP Jetdirect Print Servers - Practical IPv6 Deployment for Printing an - Page 21

IPv4/IPv6 Network

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Figure 76 - IPv4/IPv6 Network Let's break down the IP addresses on this network (NOTE: this is not a listing in DNS, only the IP addresses assigned to the nodes in Figure 16): • vista1 192.168.1.21, 2001:db8:1::21, fe80::21 • vista2 192.168.1.22, 2001:db8:1::22, fe80::22 • mfp1 192.168.1.23, 2001:db8:1::23, fe80::23 • mfp2 192.168.2.100, 2001:db8:2::100, fe80::100 • WINS 192.168.2.254, (no IPv6) • DNS 192.168.2.253, (no IPv6) • DHCPv4 192.168.2.252 (no IPv6) With the addition of these IPv6 addresses, the name resolution algorithm used by Vista will change slightly. The change happens in DNS. Let's look at the command "ping mfp2.example.internal" • Vista1 asks the DNS server for the A record of the name "mfp2.example.internal". Depending on the result code returned, Vista1 may also ask for the AAAA record of "mfp2.example.internal" The important thing about this algorithm change is that Vista1 asks for an A record first. There are two scenarios that are important: 1) The DNS server has no A record and no AAAA record for mfp2.example.internal and 2) the DNS server has no A record for mfp2.example.internal but does have an AAAA record for mfp2.example.internal. The DNS server result code in the response will be different depending on what records are in its database and Vista1 will know whether to try LLMNR or query the DNS server for the AAAA record. If both records exist, Vista1 will get both the IPv4 address and the IPv6 address. By default, Vista's resolver will list the IPv6 addresses before the IPv4 addresses when presenting the name resolution results to the client application (NOTE: this behavior can be changed - refer to Appendix A). In our example, the DNS server only has an IPv4 address which Vista1 will use to ask the DNS server name resolution questions. Therefore, Vista1 is asking for IPv6 information over the IPv4 protocol. This network behavior is perfectly valid. DNS resolvers and servers are not supposed to make any assumptions about record types and the underlying transport. A DNS resolver can ask for A records over IPv6 or AAAA records over IPv4. 21

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21
Figure 76 - IPv4/IPv6 Network
Let’s break down the IP addresses on this network (NOTE: this is not a listing in DNS, only the IP
addresses assigned to the nodes in Figure 16):
•
vista1 192.168.1.21, 2001:db8:1::21, fe80::21
•
vista2
192.168.1.22, 2001:db8:1::22, fe80::22
•
mfp1
192.168.1.23, 2001:db8:1::23, fe80::23
•
mfp2
192.168.2.100, 2001:db8:2::100, fe80::100
•
WINS 192.168.2.254, (no IPv6)
•
DNS
192.168.2.253, (no IPv6)
•
DHCPv4
192.168.2.252 (no IPv6)
With the addition of these IPv6 addresses, the name resolution algorithm used by Vista will change
slightly.
The change happens in DNS.
Let’s look at the command “ping mfp2.example.internal”
•
Vista1 asks the DNS server for the A record of the name “mfp2.example.internal”.
Depending on the result code returned, Vista1 may also ask
for the AAAA record of
“mfp2.example.internal”
The important thing about this algorithm change is that Vista1 asks for an A record first.
There are
two scenarios that are important: 1) The DNS server has no A record and no AAAA record for
mfp2.example.internal and 2) the DNS server has no A record for mfp2.example.internal but does
have an AAAA record for mfp2.example.internal.
The DNS server result code in the response will be
different depending on what records are in its database and Vista1 will know whether to try LLMNR
or query the DNS server for the AAAA record.
If both records exist, Vista1 will get both the IPv4
address and the IPv6 address.
By default, Vista’s resolver will list the IPv6 addresses before the IPv4
addresses when presenting the name resolution results to the client application (NOTE: this behavior
can be changed – refer to Appendix A).
In our example, the DNS server only has an IPv4 address which Vista1 will use to ask the DNS
server name resolution questions.
Therefore, Vista1 is asking for IPv6 information over the IPv4
protocol.
This network behavior is perfectly valid.
DNS resolvers and servers are not supposed to
make any assumptions about record types and the underlying transport.
A DNS resolver can ask for
A records over IPv6 or AAAA records over IPv4.