User guide

September 2009
Page 48 of 79 OmniSwitch 6400/6850/6855/9000/9000E—Release 6.4.2.R01
The stack provides support for all idle switches during primary switch failover. In other words, if the
primary switch in the stack fails or goes offline for any reason, all idle switches will continue data
transmission during the secondary switch’s takeover process..
MAC Retention - The MAC Retention functionality is implemented to enhance Smart Continuous
Switching for stackable products by retaining the base MAC address of the primary stack element
during a takeover. As a result, both L2 and L3 traffic as well as the associated control protocols (e.g.
routing protocols, spanning tree) will be minimally affected during takeover.
There are also additional enhancements to MAC Retention for avoiding duplicate MAC scenarios. If
the primary element is not returned to the stack after a preset time, a trap will be generated indicating
the possibility of a duplicate MAC. A duplicate MAC scenario would occur if the primary element
was put back into the network since the stack has retained the primary element’s MAC address.
Smart Continuous Switching – Chassis-based Products
Each CMM module contains hardware and software elements to provide management functions for the
chassis. The CMM module also contains the switch fabric for the system. User data flowing from one
NI module to another passes through the switch fabric.
The OS9600 operates with one CMM, the other chassis contain two CMM slots.
If there are two CMM modules in a chassis, one management processor is considered “primary” and is
actively managing the system. The other management processor is considered “secondary” and remains
ready to quickly take over management in the event of hardware or software failure on the primary. In
the event of a failure, the two processors exchange roles and the secondary takes over as primary.
The switch fabric on the CMM operates independently of the management processor. If there are two
CMM modules installed in a chassis, both fabric modules are normally active. Two CMM modules
must be installed in the chassis to provide full fabric capacity. However, note that only the one CMM
module in the OS9600 provides full fabric capacity.
If there is one CMM module installed in a chassis, then there is a single management processor, but
there is no “secondary” CMM. Hardware or software failures in the CMM may result in a system
reboot. The system fabric capacity on a system with one CMM is only half of the fabric capacity of a
dual CMM system.
SNMP
The Simple Network Management Protocol (SNMP) is an application-layer protocol that allows
communication between SNMP managers and SNMP agents on an IP network. Network administrators
use SNMP to monitor network performance and to solve network problems. SNMP provides an
industry standard communications model used by network administrators to manage and monitor their
network devices. The OmniSwitch supports SNMPv1, SNMPv2, and SNMPv3.
Source Learning
Source Learning builds and maintains the MAC address table on each switch. New MAC address table
entries are created in one of two ways: they are dynamically learned or statically assigned.
Dynamically learned MAC addresses are those that are obtained by the switch when source learning
examines data packets and records the source address and the port and VLAN it was learned on. Static
MAC addresses are user defined addresses that are statically assigned to a port and VLAN.
In addition, Source Learning also tracks MAC address age and removes addresses from the MAC
address table that have aged beyond the configurable aging timer value.
Accessing MAC Address Table entries is useful for managing traffic flow and troubleshooting network
device connectivity problems.