D-Link DES-1228/ME, User Manual, Page: 101 / 267

DES-1228/ME Layer 2 Fast Ethernet Managed Switch
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Figure 7- 22. IGMP Snooping Multicast VLAN Group List Settings window
Enter a Multicast Group List for a particular entry and click Add the new IGMP Snooping Multicast VLAN Group List entry
will be displayed on the IGMP Snooping Multicast VLAN Group List table on the lower half of the window. To remove an
entry click its corresponding Delete button in the IGMP Snooping Multicast VLAN Group List table, to remove all entries click
Remove All .
Spanning Tree
This Switch supports three versions of the Spanning Tree Protocol; 802.1d STP, 802.1w Rapid STP and MSTP. 802.1d STP will
be familiar to most networking professionals. However, since 802.1w RSTP has been recently introduced to D-Link managed
Ethernet switches, a brief introduction to the technology is provided below followed by a description of how to set up 802.1d STP
and 802.1w RSTP.
802.1Q MSTP
Multiple Spanning Tree Protocol, or MSTP, is a standard defined by the IEEE community that allows multiple VLANs to be
mapped to a single spanning tree instance, which will provide multiple pathways across the network. Therefore, these MSTP
configurations will balance the traffic load, preventing wide scale disruptions when a single spanning tree instance fails. This will
allow for faster convergences of new topologies for the failed instance. Frames designated for these VLANs will be processed
quickly and completely throughout interconnected bridges utilizing any of the three spanning tree protocols (STP, RSTP or
MSTP).
This protocol will also tag BPDU packets so receiving devices can distinguish spanning tree instances, spanning tree regions and
the VLANs associated with them. An MSTI ID will classify these instances. MSTP will connect multiple spanning trees with a
Common and Internal Spanning Tree (CIST). The CIST will automatically determine each MSTP region, its maximum possible
extent and will appear as one virtual bridge that runs a single spanning tree. Consequentially, frames assigned to different VLANs
will follow different data routes within administratively established regions on the network, continuing to allow simple and full
processing of frames, regardless of administrative errors in defining VLANs and their respective spanning trees.
Each switch utilizing the MSTP on a network will have a single MSTP configuration that will have the following three attributes:
A configuration name defined by an alphanumeric string of up to 32 characters (defined in the STP Bridge Global Settings
window in the Configuration Name field).
A configuration revision number (named here as a Revision Level and found in the STP Bridge Global Settings window)
and;
A 4096-element table (defined here as a VID List in the MST Configuration Table window), which will associate each of
the possible 4096, VLANs supported by the Switch for a given instance.
To utilize the MSTP function on the Switch, three steps need to be taken:
The Switch must be set to the MSTP setting (found in the STP Bridge Global Settings window in the STP Version field)
The correct spanning tree priority for the MSTP instance must be entered (defined here as a Priority in the MST
Configuration Table window when configuring an MSTI ID settings).
VLANs that will be shared must be added to the MSTP Instance ID (defined here as a VID List in the MST Configuration
Table window when configuring an MSTI ID settings).
802.1w Rapid Spanning Tree
The Switch implements two versions of the Spanning Tree Protocol, the Rapid Spanning Tree Protocol (RSTP) as defined by the
IEEE 802.1w specification and a version compatible with the IEEE 802.1d STP. RSTP can operate with legacy equipment
implementing IEEE 802.1d, however the advantages of using RSTP will be lost.