Advanced Spanning Tree Protocols (MSTP/VSTP) JN0-650 Practice Questions (Page 2)

Questions 6–10

1. 6foundation · easy

   Which Junos configuration statement is used to enable VSTP on a switch?

   • Aset protocols mstp
   • Bset protocols stp
   • Cset protocols rstp
   • Dset protocols vstp
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2. 7expert · hard

   A network has two MSTP regions (Region A and Region B) connected by two redundant links. Region A has VLANs 10-20 mapped to instance 1, and Region B has VLANs 10-20 mapped to instance 2. The engineer wants to ensure that VLAN 15 traffic is not blocked on either link. What must be true for this to happen?

   • AThe region names must be different to allow the IST to carry all VLANs between regions.
   • BThe two links must be configured as an aggregated Ethernet bundle to prevent blocking.
   • CThe revision numbers must be set to 0 to allow inter-region VLAN forwarding.
   • DThe VLAN-to-instance mappings must be consistent across both regions, or the IST will not carry VLAN 15 between regions.
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4. 8foundation · easy

   What is a known limitation of VSTP compared to MSTP?

   • AVSTP only works with a single region.
   • BVSTP does not support VLAN tagging.
   • CVSTP cannot be used with RSTP-enabled switches.
   • DVSTP requires a separate instance for each VLAN, which can increase CPU and bandwidth overhead.
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5. 9application · medium

   An engineer configures VSTP on a Junos switch with the command 'set protocols vstp vlan all'. The switch is connected to another switch running RSTP. After the configuration, the engineer notices that the RSTP switch is not receiving VSTP BPDUs on the shared link. What is the most likely reason?

   • AThe 'vlan all' configuration is invalid; VSTP requires explicit VLAN lists, and the command failed silently.
   • BVSTP BPDUs are sent with a multicast address that RSTP switches do not recognize, so the RSTP switch ignores them and runs its own RSTP instance.
   • CVSTP is disabled by default on Junos switches, and the engineer must also issue 'set protocols vstp enable'.
   • DThe RSTP switch is blocking the port because it detects a loop, so it drops all BPDUs from the VSTP switch.
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6. 10application · medium

   A service provider runs MSTP in its core network with multiple regions. A customer connects a legacy switch running RSTP to one of the provider's edge switches. The customer's switch is not configured for MSTP. What happens to the MSTP region when the RSTP switch is connected?

   • AThe RSTP switch joins the MSTP region automatically and participates in all MSTP instances.
   • BThe edge switch must be reconfigured to run RSTP on the port facing the customer switch, or the link will not come up.
   • CThe entire MSTP region is treated as a single RSTP bridge by the legacy switch, and the regional boundary is formed at the edge switch's port.
   • DThe MSTP region is split into two regions because the RSTP switch has a different region configuration.
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