Alteon Application Switch Operating System Application Guide
Load Balancing Special Services
288
Document
ID:
RDWR-ALOS-V2900_AG1302
4. Apply and save your configuration.
Layer 7 DNS Load Balancing
The Internet name registry has become so large that a single server cannot keep track of all the
entries. This is resolved by splitting the registry and saving it on different servers.
If you have large DNS server farms, Alteon lets you load balance traffic based on DNS names, DNS
query types and DNS versus DNSSEC queries. To load balance DNS queries, the DNS protocol
elements are extracted from the query, processed by Alteon DNS Layer 7 processing engine, and the
request is sent to the appropriate real server.
Layer 7 DNS load balancing is supported for TCP/DNS and UDP/DNS (stateful) in a pure IPv4
environment (IPv4 clients and servers), and UDP/DNS (stateful) in a pure IPv6 environment (IPv6
clients and servers). For UDP stateful DNS load balancing, Alteon creates session entries in its
session table, and removes them when a response is sent from the server to the client.
For example, as illustrated in
Figure 43 - Load Balancing DNS Queries, page 289
a DNS server farm
load balances DNS queries based on DNS names.
•
Regular DNS requests with DNS names beginning with A through G and N through T are sent to
Server 1.
•
DNS names beginning with H through M and U through Z are sent to Server 2.
•
Server 3 is an old DNS server not supporting DNSSEC queries and answers DNS queries of types
MX, AAAA and A for all hostnames.
•
Server 4 supports only DNSSEC queries and answers DNS types A, AAAA, MX and DNSKEY for all
hostnames.
>> Virtual Server 2 DNS Service# protocol tcp
>> Virtual Server 2 DNS Service# apply
>> Virtual Server 2 DNS Service# save
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