EDS-508 Series User’s Manual Featured Functions
3-27
result from link failures. For example, the following figure shows a network containing VLANs 1
and 2. They are connected using the 802.1Q-tagged link between Switch B and Switch C. By
default, this link has a port cost of 100 and is automatically blocked because the other
Switch-to-Switch connections have a port cost of 36 (18+18). This means that both VLANs are
now subdivided—VLAN 1 on Switch units A and B cannot communicate with VLAN 1 on Switch
C, and VLAN 2 on Switch units A and C cannot communicate with VLAN 2 on Switch B.
To avoid any VLAN subdivision, it is recommended that all inter-Switch connections are made
members of all available 802.1Q VLANs to ensure connectivity at all times. For example, the
connections between Switches A and B, and between Switches A and C should be 802.1Q tagged
and carrying VLANs 1 and 2 to ensure connectivity.
For more information about VLAN Tagging, see the section Configuring Virtual LANs.
Configuring STP/RSTP
The following figures indicate which Spanning Tree Protocol parameters can be configured. A
more detailed explanation of each parameter is given below.
VLAN1
VLAN1
VLAN2
VLAN1
VLAN2
Switch C Switch B
100Base TX
full-duplex Link
carry VLAN1
only (path cost
=18)
100Base TX
full-duplex Link
carry VLAN2 only
(path cost =18)
802.1Q tagged,
10Base Tx
half-duplex Link
carry VLAN1, 2
(path cost =100)
Block
VLAN2
Switch A
