Router R1 Cannot Reach R3 Practice Questions

Port Security

Why wrong: Port Security uses MAC address tables, not DHCP snooping bindings.

Private VLANs

Why wrong: Private VLANs are a Layer 2 isolation technique, not dependent on DHCP snooping.

MACsec

Why wrong: MACsec provides encryption and is independent of DHCP snooping.

role name zone-viewer feature zone; permit command configure terminal ; zone name etc.

Why wrong: Incorrect syntax; 'feature zone' is not a valid command for role configuration.

role name zone-viewer rule 1 permit read-write; feature zone

Why wrong: This uses rule-based syntax not applicable to MDS; also read-write would allow changes.

role name zone-viewer permit command zone; permit command zoneset; permit command zone-create

Why wrong: These commands are for configuration, which would allow modification.

OSPF hello timer mismatch.

Why wrong: Hello timer mismatch would prevent adjacency from forming.

MTU mismatch on the fabric links.

Why wrong: MTU mismatch can cause problems but not typically flapping.

Incorrect area configuration.

Why wrong: Incorrect area would prevent adjacency entirely.

broadcast

Why wrong: Default type but adds DR election overhead.

non-broadcast

Why wrong: Requires manual neighbor commands, not recommended for simple links.

point-to-multipoint

Why wrong: Used for hub-and-spoke topologies, not direct links.

First, configure the router ID before creating the OSPF process, then create the process, then enable on interfaces, then verify.

Why wrong: This is incorrect because setting the router ID requires an existing OSPF process; otherwise the command fails or is ignored.

First, create the OSPF process, then enable OSPF on interfaces, then configure the router ID, then verify.

Why wrong: This is incorrect because enabling OSPF on interfaces before setting the router ID may result in a dynamically assigned router ID, which is not deterministic and may change after reload.

First, enable OSPF on interfaces, then create the OSPF process, then set router ID, then verify.

Why wrong: This is incorrect because OSPF cannot be enabled on interfaces if the OSPF process does not exist yet.

Dynamic ARP Inspection (DAI)

Why wrong: DAI validates ARP packets, not DHCP.

Control Plane Policing (CoPP) dropping DHCP packets

Why wrong: CoPP might drop if rate-limited, but DHCP is typically not rate-limited aggressively.

Port security with maximum MAC limit

Why wrong: Port security limits MACs but does not block DHCP.

The CoPP policy is applied to the wrong interface

Why wrong: CoPP is applied to the control plane, not an interface, so incorrect application is unlikely.

The CoPP policy rate-limits all traffic including OSPF below its needed rate

Why wrong: Rate-limiting would still allow some packets; complete dropping of OSPF indicates a drop action, not rate-limit exceed.

The class-map matches multiple protocols including OSPF

Why wrong: If the class-map explicitly matches ICMP via protocol or ACL, it should not match OSPF. However, a poorly designed ACL could cause this.

address-family vpnv4 unicast

Why wrong: VPNv4 is for MPLS Layer 3 VPNs.

address-family ipv4 unicast

Why wrong: This carries IPv4 routes, not EVPN MAC/IP info.

address-family link-state

Why wrong: Link-state is for OSPF, not EVPN.

ip ospf dead-interval 30

Why wrong: 30 is not 10.

ip ospf hello-interval 10

Why wrong: Sets hello interval, not dead.

ip ospf dead-interval 40

Why wrong: 40 is default, not 10.

Increase the link timeout interval on the switch port

Why wrong: Temporary masking of the symptom.

Configure the switch port speed to auto-negotiate

Why wrong: Auto-negotiation is not standard in FC and does not fix SFP issues.

Change the admin state of the interface to shut and no shut

Why wrong: This does not address the underlying physical issue.

Terraform

Why wrong: Terraform is an IaC provisioning tool, not version control.

Jenkins

Why wrong: Jenkins is a CI/CD server, not version control.

Ansible

Why wrong: Ansible is an automation tool, not version control.

The MDS does not have a route to the FCoE initiator's VSAN

Why wrong: The initiator and target are in the same VSAN, so routing is irrelevant.

The FCoE initiator is not using the correct VN_Port MAC address

Why wrong: If the MAC were incorrect, the initiator would not appear in the FCoE database.

The FCoE NPV is not enabled on the Nexus

Why wrong: NPV is not required for this topology; the Nexus is in FCoE mode, not NPV.

Configure passive-interface default under OSPF.

Why wrong: Passive interface suppresses OSPF adjacencies, not DR election.

Set ospf network type to point-to-multipoint.

Why wrong: Point-to-multipoint still elects DRs in some scenarios.

Set ospf priority to 255 on the spine interfaces.

Why wrong: Priority 255 increases the chance of becoming DR.

broadcast

Why wrong: Broadcast requires DR/BDR election and is slower on point-to-point links.

point-to-multipoint

Why wrong: Point-to-multipoint is used when one interface connects to multiple, not for direct spine-leaf.

non-broadcast

Why wrong: Non-broadcast is used for NBMA networks, not point-to-point.

IOM (FEX)

Why wrong: IOM aggregates traffic but does not handle Fibre Channel mapping.

CIMC

Why wrong: CIMC manages rack servers, not UCS B-series blade mapping.

UCS Manager

Why wrong: UCS Manager configures the mapping but the FI performs the mapping.