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Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 12 Configuring Resilient Ethernet Protocol
Configuring Resilient Ethernet Protocol (REP)
Port Role for the other failed port shows as Fail No Ext Neighbor. When the external neighbors for
the failed ports are configured, the ports go through the alternate port state transitions and eventually
go to an open state or remain as the alternate port, based on the alternate port election mechanism.
• REP ports must be Layer 2 ports.
• Be careful when configuring REP through a Telnet connection. Since REP blocks all VLANs until
another REP interface sends a message to unblock the VLAN, you might lose connectivity to the
router if you enable REP in a Telnet session that accesses the router through the REP interface.
• If you connect an STP network to the REP segment, be sure that the connection is at the segment
edge. An STP connection that is not at the edge could cause a bridging loop because STP does not
run on REP segments. All STP BPDUs are dropped at REP interfaces.
• You must configure all ports in the segment with the same set of allowed VLANs, or a
misconfiguration occurs.
• REP ports follow these rules:
–
There is no limit to the number of REP ports on a switch; however, only two ports on a switch
can belong to the same REP segment.
–
If only one port on a switch is configured in a segment, the port should be an edge port.
–
If two ports on a switch belong to the same segment, they must be both edge ports, both regular
segment ports, or one regular port and one edge no-neighbor port. An edge port and regular
segment port on a switch cannot belong to the same segment.
–
If two ports on a switch belong to the same segment and one is configured as an edge port and
one as a regular segment port (a misconfiguration), the edge port is treated as a regular segment
port.
• REP interfaces come up and remain in a blocked state until notified that it is safe to unblock. You
need to be aware of this to avoid sudden connection losses.
• You should configure service instance with encapsulation corresponding to the REP admin VLAN
and associate it to arbitratory Bridge Domain. This explicit configuration of EFP gives you the
flexibility to choose the bridge domain of your choice.
• REP sends all LSL PDUs in untagged frames on the native VLAN. The BPA message sent to the
Cisco multicast address is sent on the administration VLAN, which is VLAN 1 by default.
• You can configure how long a REP interface remains up without receiving a hello from a neighbor.
You can use the rep lsl-age-timer value interface configuration command to set the time from 120
ms to 10000 ms. The LSL hello timer is then set to the age-timer value divided by three. In normal
operation, three LSL hellos are sent before the age timer on the peer switch expires and searches for
hello messages.
• You can configure how long a REP interface remains up without receiving a hello from a neighbor.
You can use the rep lsl-age-timer value interface configuration command to set the time from 120
ms to 10000 ms. The LSL hello timer is then set to the age-timer value divided by three. In normal
operation, three LSL hellos are sent before the age timer on the peer switch expires and searches for
hello messages.
• REP ports cannot be configured as one of these port types:
–
SPAN destination port
–
Private VLAN
–
Tunnel port
–
Access port
• There is a maximum of 128 REP segments per router.