Specifications

Engineering Guidelines
250
be equally configured. The Ethernet switch ports must not be set to portfast because the 3300
ICP is an active device in this protocol.
When multiple connections are made to the 3300 ICP, the ports should have:
• No Portfast: that is, Portfast must be disabled
• One of three Spanning Tree Protocols enabled:
a. Spanning Tree Protocol (802.1D): spanning-tree mode pvst (Per VLAN Spanning
Tree).
b. Rapid Spanning Tree: spanning-tree mode fast-pvst (Fast Per VLAN Spanning
Tree).
c. Multiple Spanning Tree Protocol: spanning-tree mode mst.
Multiple Spanning Tree Protocol (IEEE802.1s, now IEEE802.1Q-2005) allows a group of VLANs
to be covered by a single message, removing multiple broadcasts for each VLAN. MSTP is
backwards compatible with Rapid Spanning Tree Protocol and Spanning Tree Protocols. RSTP
and STP devices are treated as part of the Common Spanning Tree Instance.
Some network switches may not provide the option for fast-pvst, providing only the mst option.
Rapid Spanning Tree Protocol is inherent in the mst configuration. MST is the preferred option,
if available. Following a re-configuration of network connections to the 3300 ICP, the backup
link may take a number of seconds (typically up to 50) to become stable.
Applications and other voice servers
There are a number of other applications that reside on dedicated voice servers. An example
might be
MiCollab Client or voice mail. The network connections of these servers may not be
capable of supporting VLANs directly, or having multiple devices on the same LAN connection.
Thus, the network configuration for an application server should be configured as an access
port with the Native VLAN set to apply tagging (802.1Q) to the voice VLAN. Where there is only
a single connection to the server, STP should be turned off or configured to portfast, if practical.
Often a server will have multiple NIC interfaces and these can be ‘bonded’ to provide a single
logical interface to the application but multiple physical connections to the network equipment.
Typically a protocol such as LACP, or IEEE802.1AX-2008 (formerly IEEE802.3ad), will be used
to cross link these connections. The protocol has a number of variations including active/passive
operation as well as load balancing operation, for increased throughput when multiple links are
active. The Layer2 switches should also support the same protocol and settings, as the switch
MAC address tables are used to route the data to the appropriate switch and port. The layer2
switches should be directly connected and in the same layer 2 broadcast domain.
Table 77: Multiple Network Connections
Product Release Multiple Network Connections Loop Handling in 3300 ICP
Release MCD 4.0 and
higher
Yes Basic STP