Explanation:
Full-duplex communication occurs when workstations can send and receive data simultaneously. To support full-duplex communication, both communicating hosts should be configured to transmit in full-duplex mode. With the use of full-duplex communication, the bandwidth can effectively be doubled. Hubs are not capable of handling full-duplex communication, and you need a dedicated switch port to allow full-duplex communication.

Half-duplex is the term used for the Ethernet communication mechanism when hosts can send or receive data, but not simultaneously.

Explanation:
Default routes are to route packets that are destined for networks not listed in the routing table. Also, default routes are ideal for use in stub networks. Stub networks are those that have only one adjacent router interface and therefore only one interface to send any packet, regardless of destination. When used in this fashion the default route will be the only route in the routing table.

The following statements are also true of default routes:
A default route is also known as the gateway of last resort.
The default route in Internet Protocol Version 4 (IPv4) is represented as 0.0.0.0/0.

The option stating that default routes are used to route packets destined only for networks that are listed in the routing table is incorrect. Default routes are used for routing packets that are destined for networks not listed in the routing table.

The option stating that default routes should not be used in a stub network is incorrect. Default routes are helpful in topologies where it is not necessary to learn specific networks, making them ideal for use in a stub network.
The option stating that network security is increased by using default routes is incorrect. Default routes are not concerned with enhancing network security.

Explanation:
The “r” in the output of the show cdp neighbors command is a capability code that represents a repeater. The capability codes from the output of the show cdp neighbors command along with their descriptions are:

Capability Codes: R – Router, T – Trans Bridge, B – Source Route Bridge S – Switch, H – Host, I – IGMP, r – Repeater

Explanation:
Virtual LANs (VLANs) split the network into separate broadcast domains, as would a router. VLANs are a software implementation embedded in a switch’s software that allows the switch’s hardware to switch packets only to ports that belong to the same VLAN.

Neither a switch nor a bridge splits the network into separate broadcast domains. Both a switch and a bridge are used to create collision domains for each connected node. Collision domains confine traffic destined to or coming from a particular host to the switch port of that node in the switch. This reduces collisions, which in turn decreases retransmissions and elevates throughput. Switches work at Layer 2 in the OSI model and perform the function of separating collision domains. Neither switches nor bridges filter broadcasts and distribute them across all ports.

A hub does not split the network into separate broadcast domains. A hub regenerates signal when it passes through its ports, which means that it acts as a repeater and port concentrator only. Hubs and repeaters are Layer 1 devices that can be used to enlarge the area covered by a single LAN segment, but cannot be used to segment the LAN as they have no intelligence with regards to either MAC addresses or IP addresses. Hubs provide a common connection point for network devices, and connect different network segments. Hubs are generally used for LAN segmentation. Hubs work at Layer 1 of the OSI model, which is the physical layer. Hubs do not filter broadcasts or create collision domains.

Explanation:
The Etherchannel will be created if the other end is set to desirable mode. The configuration shown in the example is using Port Aggregation protocol (PAGP). This protocol has two settings: desirable and auto. Two ends will negotiate and will only create an Etherchannel under two conditions: if one end is set to auto and the other end is set to desirable, or if both ends are set for desirable.

It will not form an Etherchannel if the other end is set to auto mode. When both ends are set to auto mode, an Etherchannel will not form.

It will not form an Etherchannel if the other end is set to on mode. On mode disables negotiation of any kind, which will prevent an Etherchannel from forming unless the other end is also set for on.

It will not form an Etherchannel if the other end is set to passive mode. Passive is a setting used in Link Aggregation Protocol (LACP). The two protocols are not compatible.

Explanation:
An inside local address is the NAT term that is used to describe the IP address assigned to a host on the inside network. It is usually a private IP address. An inside global address is the registered IP address assigned by the ISP, which represents one or more inside local IP addresses externally.
An outside local address is the IP address of an external host as it appears to the internal network.

An outside global address is the IP address assigned to a host on the external network by the host owner. The address is allocated from a globally routable address space.

NAT enables companies to use one IP addressing scheme within their network but translate those IP addresses for external communication. Static NAT assigns a permanent one-to-one mapping of local addresses to global addresses. Dynamic NAT assigns address mappings by using a pool of available addresses. NAT overloading or Port Address Translation (PAT) reduces the number of global addresses required by allowing multiple local hosts to share a global address.

Explanation:
The most likely problem is that you configured an incorrect IP address for the DNS server. Although it is impossible to know without executing the show run command, the other options can all be eliminated, making this the most likely option.

Even if the router has an incorrect default gateway, or has no default gateway configured, the router should be able to connect to resources by name if it can connect to them by IP address. The gateway will only be required if the DNS server is in a network not found in the routing table of the local router. Since the network containing the DNS server is directly connected, that network is automatically in the routing table.

The ip domain lookup command is enabled by default, so it does not need to be executed. If the scenario had not stated that all defaults were in place, it could be verified with the show run command as shown below, where line 4 indicates the ip domain lookup command is disabled:

routera# show run

hostname routera

no ip domain lookup
ip domain name acme.com
ip name-server 192.31.1.6

It is not required to have an IP helper address for DNS to function for the router. It is only required by the non-routing devices connected to the router, and only for those that are not on the same network with their DHCP server.

Explanation:
A straight-through cable is a normal four-pair cable with the same order of pin configuration on both ends. These are usually used to connect a computer to the switch or hub’s Ethernet ports.

A rollover cable, also known as rolled cable or Cisco console cable, is used to connect a computer terminal to the console port of a router. The cable pin order at one end of the cable is the reverse of the order at another end. Pin 1 is connected to pin 8, pin 2 to pin 7, and so on.

A crossover cable is used to connect two similar devices such as a computer to computer or a switch to a switch, and a computer to a router’s Ethernet port.

A serial cable is used on a router’s wide area network (WAN) interface to connect to the serial ports. Cisco serial cables generally have a male DB-25 connector on one end and a female DB-25 connector on the other.

Explanation:
Link Control protocol (LCP) has the primary responsibility of negotiating and maintaining a PPP connection. LCP, defined in Request for Comments (RFCs) 1548 and 1570, has the primary responsibility to establish, configure, authenticate, and test a PPP connection. LCP negotiates the following when setting up a PPP connection:
Authentication method used (PAP or CHAP), if any Compression algorithm used (Stacker or Predictor), if any Callback phone number to use, if defined
Multilink; other physical connections to use, if configured

The ability to utilize compression, authentication, and multilink are three options that make PPP a popular choice for Layer 2 encapsulation over a WAN link.

Network Control Protocol (NCP) defines how the two PPP peers negotiate with network layer protocols, such as IP and IPX, will be used across the PPP connection. LCP is responsible for negotiating and maintaining a PPP connection whereas NCP is responsible for negotiating upper-layer protocols that will be carried across the PPP connection.

In summary, the three steps in the establishment of a PPP session are: Link establishment phase
Optional authentication phase Network layer protocol phase

Basic Rate Interface (BRI) and Integrated Services Digital Network (ISDN) are not components of PPP, so these options are incorrect. BRI is a type of ISDN connection that contains three circuits, two 64K B or bearer channels, and one D or Delta channel. ISDN circuits are a type of WAN connection.