Spanning Tree Protocol; Multiple Spanning Tree Protocol - Avaya 2330 Manual

Layer 2 fundamentals
broadcast packets and protocols should be forwarded by the router. The Multiple IP Helper
feature provides this functionality.
Multiple IP Helper is useful when UDP broadcasts are sent to a DNS server by a network host.
If the network host happens to reside on a segment without a DNS server, the UDP broadcast
fails. A helper address is configured and a protocol assigned to an interface. The exceptions
to this are DHCP and BOOTP broadcasts, which are handled by DHCP Relay.
The Multiple IP Helper feature is implemented on primary ethernet interfaces and VLAN-
enabled ethernet sub-interfaces, with a maximum of six helper addresses can be configured
for each interface.

Spanning Tree Protocol

The operation of the Spanning Tree Protocol (STP) is defined in the IEEE Standard 802.1D.
The STP detects and eliminates logical loops in a bridged or switched network. When multiple
paths exist, the spanning tree algorithm configures the network so that a bridge or switch uses
only the most efficient path. If that path fails, the protocol automatically reconfigures the
network to make another path active. The process maintains network operations. You can
control path redundancy for VLANs by implementing STP.

Multiple Spanning Tree Protocol

The Secure Router 2330/4134 supports Multiple Spanning Tree Protocol (MSTP), and it is
enabled by default. MSTP on the Secure Router 2330/4134 is backward-compatible with STP
and Rapid Spanning Tree Protocol (RSTP). STP and RSTP can be implemented on a per-port
basis on the Secure Router 2330/4134.
MSTP defines an extension to RSTP that further develops the usefulness of VLANs. This "per-
VLAN" MSTP configures a separate Spanning Tree for each VLAN group and blocks the links
that are redundant within each Spanning Tree.
If there is only one VLAN in the network, single (traditional) STP works appropriately. If the
network contains more than one VLAN, the logical network configured by single STP would
work, but it is possible to make better use of the redundant links available by using an alternate
spanning tree for different (groups of) VLANs. MSTP allows the formation of MST regions that
can run multiple MST instances (MSTI). Multiple regions and other STP bridges are
interconnected using one single common spanning tree (CST).
MSTP on the Secure Router 2330/4134 interoperates with Cisco's implementation of MSTP.
The Cisco equipment must have IOS v12.2 (25), or newer, installed.
34 Configuration — Layer 2 Ethernet
Comments? infodev@avaya.com
July 2013