Spanning Tree; Configuration Data; Figure 4. Connecting Vlans To Atm - Cabletron Systems SSIM-A2-01 Installation And User Manual

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If you connect to the same ATM ELAN more than once from the same VLAN, you
are using parallel bridges. When doing so, you must always enable the Spanning
Tree function for all the CRFs that have parallel paths.
With more than one uplink, you can connect more VLANs to ATM while at that
same time creating backup connections. Figure 4 shows two uplink modules, each
connected to two ATM ELANs. The lighter arrow shows the parallel path in the
spanning tree "blocked" state (the path is on "standby").

Figure 4. Connecting VLANs to ATM

Spanning Tree

If you create parallel paths in your network topology, but fail to enable the spanning
tree protocol, you risk "broadcast storms" that can disrupt your entire network. To
enable spanning tree, see section "Spanning Tree Menu" in the STS16-20RM
switch manual. The default setting for spanning tree is disabled.

Configuration Data

When you configure an uplink module in a switch, the configuration data is applied
to any uplink in that particular switch slot. This means that the configuration data
does not move with the uplink module if the module is moved to another slot or
another switch. Conversely, configuration data is retained if one uplink is replaced
with another.
Note, however, that the SSIM-Ax-01 module software image is stored in the
module itself and will follow the module when it is moved to another switch.
SmartStack SSIM-A2-01/SSIM-A8-01 Installation