Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 71)

Brocade Virtual ADX Switch and Router Guide 57
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Configuring IP parameters
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The Brocade Layer 3 Switch qualifies the host name by appending a domain name. For example,
mary.eng.company.com
. This qualified name is sent to the DNS server for resolution. If there are
four DNS servers configured, it is sent to the first DNS server. If the host name is not resolved, it is
sent to the second DNS server. If a match is found, a response is sent back to the client with the
host’s IP address. If no match is found, a “unknown host” message is returned. (Refer to
Figure 12 .)
FIGURE 12 DNS resolution with one domain name
You can create a list of domain names that can be used to resolve host names. This list can have
more than one domain name. When a client performs a DNS query all hosts within the domains on
the list can be recognized and queries can be sent to any domain on the list.
Also, the Virtual ADX device now contains a DNS cache table that contains a list of host names that
have been resolved to their IP addresses. This DNS cache table allows DNS queries to be
processed quickly. When a DNS query is made, the query can be sent to the DNS cache table. If a
match is found, the DNS query is resolved. If no match is found, the DNS query is sent to the DNS
server to be resolved before any action can be taken.
For example, in Figure 14 , the client sends a ping to “mary”, which is in the eng.company.domain.
The Brocade device appends the first domain name on the domain name list to “mary” and sends
“mary.eng.company.com” to the DNS cache table. Since “mary.eng.company.com” is in the DNS
cache table, the query is resolved quickly and the Brocade device returns the IP address of “mary”.