Communicating Between Networks Exam
Where are IPv4 address to Layer 2 Ethernet address mappings maintained on host computer?
ARP cache
What are two drawbacks to ARP?
ARP requests are broadcasts. Excessive broadcasts consume network resources (bandwidth) ARP poisoning
show ip arp (router) arp -a (windows)
Displays ARP table
Best effort
IP is inherently (permanent) unreliable because packet delivery is not guaranteed.
A computer can access devices on same network but cannot access devices on other networks. What is the probable cause of this problem?
Incorrect default gateway
Which command are used to set up secure access to router through connection to console interface?
Line console 0
Which parameter does router use to choose path to destination when there are multiple routes available?
Lower metric value associated with destination network
NAT is not needed for IPv6. Why?
Number of available IPv6 addresses is extremely large. All hosts and users can get public IPv6 addresses. No translation is necessary
What are two potential network problems that can result from ARP operation?
On large networks with low bandwidth, multiple ARP broadcasts could cause data communication delays. Network attackers could manipulate MAC address and IP address mappings in ARP messages with the intent of intercepting network traffic.
Two jobs of router
Packet forwarding Packet selection
Secure remote Telnet/SSH access
Router(config-line)# line vty 0 4 Router(config-line)# password password Router(config-line)# login Router(config-line)# transport input {ssh | telnet}
Running-config mode
Stored in Random Access Memory (RAM). Reflects current configuration Affects operation of Cisco device immediately
The command "ip default-gateway 192.168.1.1" is issued on a switch. What is the result?
Switch can be managed remotely from host on another network.
Connectless
There is no connection with destination established before sending data packets.
Which field in IPv4 header is used to prevent packet from traversing network and endlessly limit lifetime of packet?
Time to live
What does ARP force all ethernet NICs to process and ARP request?
When it's broadcast frame (FF-FF-FF-FF-FF-FF)
R1(config-if)# mode
ip address 192.168.4.4 255.255.255.0
R1(config-line)# mode
login
What routing table entry has next hop address associated with destination network?
remote routes
What are two services provided by OSI (Open Systems Interconnection) network layer?
routing packets toward destination encapsulating PDUs from transport layer
What are two functions of NVRAM?
to retain (keep) contents when power is removed to store startup configuration file
Which term describes field in IPv4 packet header that contains 4-bit binary value set to 0100?
version
Purpose of configuring switch with default gateway address
Default gateway address is used to forward data originating from switch to remote networks
The IP protocol handles missing and out of sequence packets
False
The default gateway is incorrectly configured on host. What is the result?
Host will not be able to communicate with hosts on remote networks
Perform POST and load bootstrap program.
Phase 1
SSH
Remote access method that uses encryption
What information does pinging loopback address provide?
TCP/IP stack on device is working correctly
What is the aim of ARP spoofing attack?
To associate IP addresses to wrong MAC address
Line Configuration Mode
Used to configure console, SSH, Telnet, or AUX access.
User EXEC mode
Allows only limited number of basic monitoring commands but does not allow execution of any commands that might change configuration of device referred to as "view-only" mode.
ARP poisoning
Attack that spoofs (trick) legitimate user's MAC address and intercept traffic
What does command "arp-d*" do when issued on PC?
Clears ARP cache
What happens when transport input ssh command is entered on switch vty lines?
Communication between switch and remote users is encrypted.
What are some characteristics of IP protocol
Connectless Best effort Media independent
What information in ethernet frame header is examined by switch to make forwarding decision What important information is examined in Ethernet frame header by Layer 2 device in order to forward data onward?
Destination MAC address
When will a switch flood frame out of every port?
Destination MAC address FF-FF-FF-FF-FF-FF Frame's destination MAC address is not switch's CAM table
Under which two circumstances will a switch flood a frame out of every port except the port that the frame was received on?
Destination address is unknown to switch Frame has broadcast address as destination address
Name the field in IPv4 packet header used to determine priority of packet?
Differentiated services
show ip interfaces
Displays IPv4 statistics for all interfaces on router
show ipv6 interface
Displays IPv6 statistics for all interfaces on router
show ip interface brief show ipv6 interface brief
Displays all interfaces, their IP addresses, and their current status
show ip route show ipv6 route
Displays contents of IP routing tables stored in RAM
show interfaces
Displays statistics for all interfaces on device. Only displays IPv4 addressing information
What is one advantage that IPv6 simplified header offers over IPv4?
Efficient packet handling
How is ARP utilized by hosts on LAN to send traffic to remote networks?
Enables them to discover MAC address of default gateway.
A new network administrator has been asked to enter banner message on Cisco device. What is the fastest way a network administrator could test whether banner is properly configured?
Exit privileged EXEC mode and press Enter .
When transporting data from real-time applications, such as streaming audio and video, which field in IPv6 header can be used to inform routers and switches to maintain same path for packets in same conversation?
Flow label
Physical layer
Lowest, or first, layer of OSI model. Generate and detect signals so as to transmit and receive data over network medium. Set data transmission rate and monitor data error rates, but do not provide error correction.
Which two types of IPv6 messages are used in place of ARP for address resolution?
Neighbor solicitation Neighbor Advertisement
Encapsulation
Network layer encapsulates protocol data unit (PDU) from transport layer into packet. Adds IP header information, such as IP address of source (sending) and destination (receiving) hosts. Performed by source of IP packet.
Media independent
Operation is independent of medium (i.e., copper, fiber-optic, or wireless) carrying data.
Locate and load Cisco IOS software.
Phase 2
Locate and load startup configuration file or enter setup mode.
Phase 3
Segmentation
Process of dividing stream of data into smaller units of transmissions over network
Console
Provides out of band access
Network layer (OSI layer 3)
Provides services to allow end devices to exchange data across networks
Provide legal notification
Router(config)# banner motd delimiter message delimiter
Save configuration
Router(config)# end Router# copy running-config startup-config
Secure user EXEC mode
Router(config)# line console 0 Router(config-line)# password password Router(config-line)# login
Secure privileged EXEC mode
Router(config)#enable secret password
Secure all passwords in config line
Router(config-line)# exit Router(config)# service password-encryption
Which term describes field in IPv4 packet header used to limit lifetime of packet?
TTL
What property of ARP causes NICs receiving ARP request to pass data portion of Ethernet frame to ARP process?
Type field 0x806 appears in header of Ethernet frame.
Interface Configuration Mode
Used to configure switch port or router network interface.
Function of address resolution protocol?
Used to determine MAC address of any host of LAN
global configuration mode
User can enter different subconfiguration modes. Each of these modes allows configuration of particular part or function of IOS device