Redundancy Protocol - Cisco 4700M Administration Manual

Information About Redundancy

Redundancy Protocol

The ACE uses a proprietary protocol to enable redundant configurations of two ACEs (peers). You can
configure a maximum of two ACEs for redundancy. Each peer appliance can contain one or more
fault-tolerant (FT) groups. Each FT group consists of two members: one active context and one standby
context. For more information about contexts, see the Cisco 4700 Series Application Control Engine
Appliance Virtualization Configuration Guide. An FT group has a unique group ID that you assign.
One virtual MAC address (VMAC) is associated with each FT group. The format of the VMAC is:
00-0b-fc-fe-1b-groupID. Because a VMAC does not change uponswitchover, the client and se rver ARP
tables do not require updating. The ACE selects a VMAC from a pool of virtual MACs available to it.
You can specify the pool of MAC addresses that the local ACE and the peer ACE use by configuring the
shared-vlan-hostid command and the peer shared-vlan-hostid command, respectively. To avoid MAC
address conflicts, be sure that the two pools are different on the two ACEs. For more information about
VMACs and MAC address pools, see the Cisco 4700 Series Application Control Engine Appliance
Routing and Bridging Configuration Guide.
Each FT group acts as an independent redundancy instance. When a switchover occurs, the active
member in the FT group becomes the standby member and the original standby member becomes the
active member. A switchover can occur for the following reasons:
•
•
•
Figure 6-1
for redundancy. The letters (A, B, C, and D) represent the active contexts in each redundancy group,
while the primed letters (A', B', C', and D') are t h e standby contexts. The contexts are evenly distributed
between the two ACEs. You always configure the active and the standby contexts on different ACEs.
Figure 6-1
N=2
# redundant groups
=2
N=2
# redundant groups
=4
Cisco 4700 Series Application Control Engine Appliance Administration Guide
6-2
The active member becomes unresponsive.
A tracked host, interface, or HSRP group fails (see the
Detection" section).
You enter the ft switchover command to force a switchover (see the
shows two possible redundancy configurations, where N is the number of ACEs configured
Even Distribution of Contexts
A
B
A
C
B'
A'
B C' D'
D A' B'
Chapter 6 Configuring Redundant ACEs
"Configuring Tracking and Failure
"Forcing a Failover" section).
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