A network administrator is planning an upgrade for a PE router that has BGP peering sessions with several CE routers. The SLA has stringent uptime requirements, so the administrator wants to…

Question

Options

• AConfigure the clear ip bgp 65514 soft in command on the PE and CE routers.
• BConfigure the bgp graceful-restart command on the PE router.
• CConfigure MPLS on the link between the PE and CE routers.
• DConfigure a VRF on each CE router on the interface that connects to the PE router.

• A
  8% (3)
• B
  70% (26)
• C
  16% (6)
• D
  5% (2)

Explanation

Option B is correct because BGP NSR (Non-Stop Routing) with SSO (Stateful Switchover) requires bgp graceful-restart on the PE router to enable it to signal its restart capability and preserve forwarding state during a route processor switchover - without tearing down BGP sessions with neighbors. This allows traffic to continue flowing while the standby RP takes over, satisfying the SLA's uptime requirements.

Why the distractors are wrong:

• A - clear ip bgp soft in is an operational reset command used to refresh inbound BGP policies; it is not a configuration step for NSR/SSO.
• C - MPLS on the PE-CE link is a transport/VPN concern and is not a prerequisite for BGP NSR; NSR works independent of the underlying forwarding technology.
• D - VRFs for MPLS VPNs are configured on the PE router, not the CE; furthermore, NSR is transparent to CE routers - they require no configuration changes.

Memory tip: Think of Graceful Restart as the PE politely telling its peers, "If I restart, hold my routes - don't withdraw them." NSR keeps the session alive internally, but bgp graceful-restart is the knob that arms that behavior on the PE side.

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