ServerIron ADX Server Load Balancing Guide
Release 12.0.00
June 15, 2009

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High Availability

High Availability
This chapter contains the following sections:
This chapter describes the High Availability feature in ServerIron.
NOTE: In high availability configurations, with Brocade hardware based SSL acceleration in either SSL Termination or SSL Proxy mode, synchronization of proxied or terminated SSL sessions is not supported.
High Availability (HA) for Server Load Balancing (SLB) consists of three ServerIron services:
Hot Standby SLB - One ServerIron is always active while the other ServerIron is always standby. Supported on both chassis and XL systems. On chassis systems, hot standby is supported only in Switch (S) code, not Router (R) code. See “Hot Standby SLB”.
Symmetric SLB - Also called active-standby VIP. Both ServerIrons can receive SLB traffic, but only the active VIP handles the L4-7 SLB, while the standby VIP functions as a standby. The VIP with the highest configured sym-priority handles the flow. Available on both chassis and XL systems, Symmetric SLB is supported in both Switch (S) code and Router (R) code. See “Symmetric SLB”.
Sym-Active SLB - True active-active. Both ServerIrons can receive SLB traffic, and both are active for the same VIP. Configuring sym-active and sym-priority on the VIP enables a device to process traffic. Sym-Active is supported only on chassis systems (not XL) in both Switch (S) code and Router (R) code. See “Sym-Active SLB”.
With Direct Server Return (DSR), return traffic is not processed by the ServerIron. Instead, the real server sends return traffic directly to the client. You can apply DSR to each of the HA scenarios (Hot Standby SLB, Symmetric SLB, and Sym-Active SLB).
NOTE: When a device is active, it responds to ARPs and processes all traffic for the VIP. When a device is acting as standby, it performs no processing functions for the specified VIP (other than session syncing with the active device, if enabled).

High Availability

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