Port Auto Recovery - Nortel 8300 User Manual

54 VLANs, Spanning Tree, and Static Link Aggregation
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For information about configuring Simple Loop Prevention Protocol, see
"Configuring Simple Loop Prevention Protocol" (page

Port auto recovery

The port auto recovery feature can automatically enable a port shut down
by SLPP, CP-Limit or Link Flap Detect. When a port with auto recovery
enabled is operationally shut down by SLPP, CP-Limit, or Link Flap Detect,
the port is enabled within a specific, configurable time delay.
Configuration — VLANs, Spanning Tree, and Static Link Aggregation using Device Manager
Copyright © 2005-2007, Nortel Networks
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The SLPP-PDU packet transmission interval is configurable from 500
to 5000 milliseconds (ms). The default packet transmission interval
is 500 ms.
After an SLPP-PDU is received on a port that is a member of a multilink
trunk, port members with SLPP-RX enabled and RX-Threshold reached,
are disabled.
The SLPP-PDU can be received by the originating CP or the peer SMLT
CP. All other switches treat the SLPP-PDU as a normal multicast packet.
The switches ignore it and forward it to the VLAN.
SLPP-PDU transmission and reception operates only on ports for which
STP is in a forwarding state (if STP is enabled on one switch in the path).
You must enable SLPP packet receive on an individual port basis to
detect a loop:
— SLPP packet reception can only be enabled on SMLT access ports
and never on SMLT IST ports or any SMLT square or full mesh
core ports.
— Vary the SLPP packet receive threshold between the two core SMLT
switches so that if a loop is detected, the access ports on both
switches do not go down, avoiding SMLT client isolation.
SLPP is port-based, so a port is disabled if it receives SLPP-PDUs on
one or more VLANs on a tagged port. For example, if the SLPP packet
receive threshold is set to five, a port is shut down if it receives five
SLPP-PDUs from one or more VLANs on a tagged port.
SLPP does not have any hardware requirements or dependencies.
SLPP does not support jumbo frames on the ERS 8300 v4.0.
SLPP does not replace the functionality of Spanning Tree Protocol,
but is a supplement to help detect and prevent loops in the SMLT
environment. Nortel recommends that you use this feature in an SMLT
environment only.
The ERS 8300 Series does not support the use of SLPP in an
LACP-SMLT environment.
Nortel Ethernet Routing Switch 8300
NN46200-510 03.01 Standard
4.0 27 August 2007
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