Foundry NetIron M2404C and M2404F Metro Access Switches
Configuring STP (Rev. 03)
Spanning Tree Protocol (STP)
© 2008 Foundry Networks, Inc.
Page 15 of 38
The error level is considered critical when the CRC error rate exceeds 1% within a 3-second
interval. When the error level reaches the critical value, the switch triggers a Spanning Tree or
Rapid Spanning Tree reconfiguration.
The Spanning Tree line error detection is disabled by default. To set the line error detection, use
the
spanning-tree line-error-detect
command in Protocol Configuration mode.
Spanning Tree IGMP Fast Recovery
Using the STP Internet Group Multicast Protocol (IGMP) Fast recovery, the Multicast traffic takes
advantage of the connectivity and convergence time provided by the Spanning Tree Protocols.
In
Figure 9
, all devices run both IGMP snooping and any one of the Spanning Tree Protocols - STP,
RSTP, MSTP. The multicast router floods traffic in the topology for multicast groups that the
client has been subscribed to. A subscription to a specific multicast group is performed by sending
IGMP reports.
Figure 9: Spanning Tree IGMP Example
The multicast router sends an IGMP query to the clients for their multicast group memberships. IP
hosts reply with IGMP Reports. The traffic flows from the router, through Switch D and Switch A,
to Switch C. All ports between switches and routers should be statically configured as mrouter
ports.