Brocade Communications Systems 12.4.00 manual Using only passive RTT

1 Round-trip times

In the example above, assume that the GSLB ServerIron ADX is configured as Mode 2. Also assume that this GSLB ServerIron ADX is providing GSLB for www.foo.com where the IP addresses for this domain are IP-1, IP-2, and IP-3. IP-1 is a VIP on ServerIron ADX-1. IP-2 is a VIP on ServerIron ADX-2. IP-3 is a VIP on ServerIron ADX-3.

If a DNS resolution request comes from LDNS 201.53.10.1, then GSLB ServerIron ADX uses only the RTT information for IP-1 which is configured on ServerIron ADX 1.1.1.102 (rtt = 7ms, source = active). Since the GSLB ServerIron ADX in configured as Mode 2, only actively reported RTT values are used during the selection. The RTTs for IP-2 and IP-3 are not used since the source of these RTTs is passive.

The RTT algorithm mode can be configured globally in a global GSLB policy or locally in a host-level GSLB policy. Placing the modes in different policies allows you to use different RTT algorithm modes for different hosts. The default RTT algorithm mode for a global or host level GSLB policy is Mode 1.

Using only passive RTT

To configure a global GSLB policy to use only passive RTT values for RTT algorithm (Mode 1), enter commands such as the following:

GSLB-ServerIronADX# configure terminal GSLB_ServerIronADX(config)# gslb policy GSLB-ServerIronADX(config-gslb-policy)# round-trip-time active-rtt use-passive-rtts-only

To configure a host-level GSLB policy to use only passive RTT values for RTT algorithm (Mode 1), enter commands such as the following:

GSLB-ServerIronADX# configure terminal GSLB-ServerIronADX(config)# gslb-host-policy test

GSLB-ServerIronADX(config-gslb-host-policy-test)# round-trip-time active-rtt use-passive-rtts-only

Syntax: round-trip-time active-rtt use-passive-rtts-only

Using only active RTT

To configure a global GSLB policy to use only active RTT values for RTT algorithm (Mode 2), enter commands such as the following:

GSLB-ServerIronADX# configure terminal GSLB_ServerIronADX(config)# gslb policy GSLB-ServerIronADX(config-gslb-policy)# round-trip-time active-rtt use-active-rtts-only

To configure a host-level GSLB policy to use only active RTT values for RTT algorithm (Mode 2), enter commands such as the following:

GSLB-ServerIronADX# configure terminal GSLB-ServerIronADX(config)# gslb-host-policy test

GSLB-ServerIronADX(config-gslb-host-policy-test)# round-trip-time active-rtt use-active-rtts-only

Syntax: round-trip-time active-rtt use-active-rtts-only

Using both active and passive RTT

To configure a global GSLB policy to use both passive and active RTT values for RTT algorithm (Mode 3), enter commands such as the following:

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