Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 75)

Brocade Virtual ADX Global Server Load Balancing Guide 65
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DNS cache proxy
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Deleting sticky GSLB session for a specific client
To delete Sticky GSLB sessions for a specific client, enter a command such as the following.
Virtual ADX#clear gslb sticky-session client-ip 10.1.1.101
Syntax: clear gslb sticky-session client-ip client-ip
The client-ip is the IP address or prefix of the client for which sticky session will be deleted.
Deleting all sticky GSLB sessions
To delete all the Sticky GSLB sessions globally, enter a command such as the following.
Virtual ADX#clear gslb sticky-session all
Syntax: clear gslb sticky-session all
For a GSLB sticky session to be synced, you must configure symmetric-port with port and VLAN
information on both the master and backup ADX devices as shown in the following.
Virtual ADX(config)#server symmetric-port ethernet 7 vlan-id 7
DNS cache proxy
The DNS cache proxy feature allows the Brocade Virtual ADX to act as a proxy for a DNS server by
responding directly to the client queries without forwarding them to the DNS server. Just as in the
GSLB DNS proxy mode, the Brocade Virtual ADX periodically queries the authoritative DNS server
for IP addresses corresponding to the domains configured for GSLB and caches them. However,
unlike GSLB DNS proxy, the Brocade Virtual ADX does not forward every client query to the
authoritative DNS server, it responds directly to the client using the cached address list for the
requested domain.
When you enable DNS cache proxy, the Brocade Virtual ADX applies the GSLB policy to the IP
addresses it has cached for the requested domain, and responds to the client with the best
address. The Brocade Virtual ADX refreshes the address cache by periodically querying the
authoritative DNS server. The default update interval is 30 seconds and is configurable.
The DNS cache proxy feature is useful in network environments where the traffic between the
Brocade Virtual ADX and the authoritative DNS server introduces noticeable latency in the
response to client requests. For example, if the Brocade Virtual ADX and the authoritative DNS
server are connected over the Internet, this feature can eliminate the delays caused by that
connection.
In configurations where the Brocade Virtual ADX and DNS server are co-located, the additional
round trip time between the Brocade Virtual ADX and DNS server is usually negligible. However, if
the Brocade Virtual ADX and DNS server are in different networks, the delay can become
significant. In this case, the DNS cache proxy can help enhance performance by eliminating the
exchange between the Brocade Virtual ADX and DNS server for responses to client queries.
The DNS cache proxy feature is disabled by default. When the feature is disabled, the Brocade
Virtual ADX forwards client requests to the actual DNS server, applies the GSLB policy to the
responses, then sends the optimized response to the client. In this case, the round trip time
between the Brocade Virtual ADX and DNS server is part of the overall round trip time between
when the client sends the request and when the client receives the response.