352-001 · Question #323
Which two design aspects should a metro service provider consider when planning to deploy REP for his backbone? (Choose two.)
The correct answer is B. UDLD can be enabled on REP interfaces to detect unidirectional failures. E. VLAN load balancing for optimal bandwidth usage is supported in any REP segment.. REP supports UDLD for unidirectional failure detection and VLAN load balancing on any segment, but does not limit segments to 7 devices or guarantee sub-50ms convergence.
Question
Which two design aspects should a metro service provider consider when planning to deploy REP for his backbone? (Choose two.)
Options
- ATwo REP segments can be connected redundantly at two points, one connection will be blocked
- BUDLD can be enabled on REP interfaces to detect unidirectional failures.
- CThe guaranteed convergence recovery time is less than 50 ms for the local segment.
- DA REP segment is limited to a maximum of seven devices.
- EVLAN load balancing for optimal bandwidth usage is supported in any REP segment.
How the community answered
(46 responses)- A11% (5)
- B80% (37)
- C2% (1)
- D7% (3)
Why each option
REP supports UDLD for unidirectional failure detection and VLAN load balancing on any segment, but does not limit segments to 7 devices or guarantee sub-50ms convergence.
REP segments connect at exactly one redundant point to form a ring; connecting two REP segments at two separate points is not a supported topology and would not result in a simple blocked port.
UDLD can be enabled on REP interfaces to detect unidirectional link failures, which REP alone cannot identify because its hello-based mechanism requires bidirectional communication to function correctly.
REP convergence is typically sub-200ms, not sub-50ms; the sub-50ms guarantee is associated with SONET/SDH and protocols like IEEE 802.17 RPR, not REP.
A REP segment supports up to 26 devices, not a maximum of seven; this low limit is inaccurate and does not reflect the REP protocol specification.
REP supports VLAN load balancing on any segment by configuring which VLANs are blocked on the alternate port, allowing bandwidth to be distributed optimally across the ring topology.
Concept tested: REP design considerations for metro Ethernet backbone deployment
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/lanswitch/configuration/xe-16/lanswitch-xe-16-book/lsw-resilient-eth-protocol.html
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