The ‘switchport voice vlan ‘ command is essential for Cisco IP Phone deployments. It creates a multi-VLAN access port. The phone uses the specified voice VLAN (e.g., 150) for its traffic, while traffic from the device connected to the phone’s PC port is placed in the data VLAN (configured with ‘switchport access vlan’). This allows a single physical port to carry two logical networks without requiring a trunk configuration to the end device.

When OSPF neighbors are stuck in EXSTART/EXCHANGE state, it typically indicates a problem during the Database Description (DBD) packet exchange phase. A mismatch in the MTU size on the connecting interfaces is a common cause. One router sends a large DBD packet that the other router cannot accept due to its smaller interface MTU, causing the adjacency process to fail. While other options can cause issues, they usually prevent the neighbor relationship from forming at all (stuck in INIT or DOWN), not specifically in EXSTART.

To configure multiple IPv4 addresses on a single physical interface (secondary addressing), the correct command is `ip address secondary`. The primary address is configured without the keyword. This allows a single router interface to belong to multiple logical IP networks. Option D creates a subinterface for 802.1Q trunking, which is a different technology used for carrying multiple VLANs, not simply adding a second IP address on the same layer-2 segment.

HDLC (High-Level Data Link Control) is the default encapsulation on Cisco serial interfaces. Cisco’s implementation is proprietary because it adds a ‘Type’ field that standard HDLC lacks. This field allows the router to multiplex multiple network layer protocols (like IP, IPX) over the same link. PPP is the protocol that is an open IETF standard, is connection-oriented, uses LCP and NCP, and supports authentication like CHAP.

The question states the client has an IP address, implying DHCP worked. The most common next-step failure for a client that has an IP but no internet access is an incorrect or missing default gateway (a Layer 3 function). The gateway is the device that routes traffic off the local subnet. While RF issues (L1) or MAC filtering (L2) could be culprits, they would typically prevent association or DHCP from working in the first place. Layer 4 issues are less likely to be the first check for basic connectivity.

To fully implement SSHv2 and disable Telnet, multiple steps are necessary. `transport input ssh` (A) is required under the VTY lines to tell the router to only accept SSH connections, not Telnet. `ip ssh version 2` (B) is required to restrict SSH connections to the more secure version 2. Generating RSA keys and creating local/AAA credentials are also prerequisites, but the question asks for the additional step after keys are generated to disable Telnet and enforce SSHv2, which encompasses both A and B.

On multi-access networks (like Ethernet), if every router formed a full OSPF adjacency with every other router, it would create n*(n-1)/2 adjacencies and cause excessive LSA flooding. The DR/BDR mechanism solves this. All routers on the segment form adjacencies only with the DR and BDR. The DR then distributes routing information to and from the other routers (DROthers), dramatically reducing the number of adjacencies and controlling LSA flooding.

When an ISP provides a static public IP address for the customer premises equipment (CPE), the standard practice is to manually configure that IP address, subnet mask, and default gateway on the router’s external interface using the `ip address ` command. Using DHCP (A) is for when the ISP dynamically assigns an address. IP unnumbered (C) is for point-to-point links where you want to conserve addresses, and bridging (D) is not typical for a router’s WAN connection as it would defeat its routing purpose.

Port security can be configured with a violation mode. The default mode is `shutdown`. In this scenario, the port is configured for a maximum of 2 MAC addresses. If a frame arrives with a source MAC address that is not one of the two learned/sticky addresses, and the maximum count (2) has already been reached, a violation occurs. In `shutdown` mode, the switch disables the port by placing it in the err-disabled state, which requires manual intervention (`shutdown`/`no shutdown`) to recover.

The ‘switchport voice vlan ‘ command is essential for Cisco IP Phone deployments. It creates a multi-VLAN access port. The phone uses the specified voice VLAN (e.g., 150) for its traffic, while traffic from the device connected to the phone’s PC port is placed in the data VLAN (configured with ‘switchport access vlan’). This allows a single physical port to carry two logical networks without requiring a trunk configuration to the end device.0