Brocade Communications Systems 12.4.00 manual Redirecting queries, Transparent DNS query intercept

Transparent DNS query intercept 1

Authoritative DNS server for domain brocade.com 209.157.23.130

4. ServerIron changes the source
address in the reply to the authoritative
DNS server.
If the reply is from a proxy DNS server,		DNS
the ServerIron also changes the
destination address from the				ServerIron configured to
ServerIron’s source IP address to the
client’s IP address.				intercept DNS queries to
			209.157.23.130
		SI			Alternative (proxy) DNS
					209.200.22.100
2. ServerIron either redirects client				Source IP address
			209.157.23.100
query to the proxy DNS server, or
intercepts and directly responds to the
query.						proxy DNS
Whether the ServerIron redirects or
directly responds to query depends on
transparent DNS configuration.
					3. If ServerIron redirects client query to
					the proxy DNS server, the DNS server
					sends response back to the
					ServerIron, to the configured source IP
					address.
	DNS
1. Client’s local DNS server				5. Client receives response. Source
sends a recursive query for				address of response is the authoritative
brocade.com.				DNS server.
				The ServerIron’s redirection or
				interception is transparent to the client.

Redirecting queries

To configure transparent DNS query intercept to redirect queries to a proxy DNS server or another GSLB ServerIron ADX:

•Configure a real server with the IP address of the proxy DNS server or other GSLB ServerIron ADX to which you want to redirect queries.

•Configure a virtual server with the IP address of the authoritative DNS server that you want to intercept.

•Specify the domain and host application for which you want to intercept queries.

•Configure an IP policy to enable the ServerIron ADX to examine incoming DNS packets.

NOTE

In standard GSLB configuration, the ServerIron ADX sends a DNS query to the DNS server to get the IP addresses for the domain and performs health-checks on them. However in this transparent intercept mode, where you do not do GSLB on the DNS response, the ServerIron ADX does not do these things.

NOTE

The ServerIron ADX intercepts queries only for domain names configured on the ServerIron ADX. For domain names that are not configured on the ServerIron ADX, the ServerIron ADX still sends queries to the authoritative DNS server.

ServerIron ADX Global Server Load Balancing Guide	97
53-1002437-01