Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 73)

Brocade Virtual ADX Switch and Router Guide 59
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Configuring IP parameters
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FIGURE 14 DNS resolution with host name not in DNS Cache Table
Over a period of time, there may be changes to the information in the DNS cache table. For
example, a host’s IP address can change, making the entries in the DNS cache table to be invalid.
The Brocade device polls each entry in the DNS cache table to determine if the information in the
DNS cache table is still valid. By default, the Brocade device sends a ping to the host every 1
minute. This polling interval can be changed.
Defining a DNS entry
You can define up to four DNS servers for each DNS entry. The first entry serves as the primary
default address. If a query to the primary address fails to be resolved after three attempts, the next
DNS server address is queried (also up to three times). This process continues for each defined
DNS server address until the query is resolved. The order in which the DNS server addresses are
polled is the same as the order in which you enter them.
Suppose you want to define the domain name of example1.com on a Layer 3 Switch and then
define four possible default DNS server addresses. To do so, enter the following commands.
Virtual ADX(config)# ip dns domain-name example1.com
Virtual ADX(config)# ip dns server-address 10.157.22.199 10.96.7.15 10.95.7.25
10.98.7.15
Syntax: ip dns server-address ip-addr [ip-addr] [ip-addr] [ip-addr]
In this example, the first IP address in the ip dns server-address... command becomes the primary
gateway address and all others are secondary addresses. Because IP address 10.98.7.15 is the
last address listed, it is also the last address consulted to resolve a query.