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CISCO
Introduction to Networks CCNA1 v7 Chapter 9 Address Resolution
| Question | Answer |
|---|---|
| What are the two primary addresses assigned to a device on an Ethernet LAN | • Physical address (the MAC address) – Used for NIC to NIC communications on the same Ethernet network. • Logical address (the IP address) – Used to send the packet from the source device to the destination device. The destination IP address may be on the same IP network as the source or it may be on a remote network. |
| What is the • Physical address (the MAC address) used for | Used for NIC to NIC communications on the same Ethernet network. |
| What is the Logical address (the IP address) used for | Used to send the packet from the source device to the destination device. The destination IP address may be on the same IP network as the source or it may be on a remote network. |
| The Layer 2 Ethernet frame contains the following: | • Destination MAC address – This is the simplified MAC address of PC2, 55-55-55. • Source MAC address – This is the simplified MAC address of the Ethernet NIC on PC1, aa-aa-aa. |
| If the destination IP address is on the same network, the destination MAC address will be that of the ? | Destination device |
| The Layer 3 IP packet contains the following: | • Source IPv4 address – This is the IPv4 address of PC1, 192.168.10.10. • Destination IPv4 address – This is the IPv4 address of PC2, 192.168.10.11. |
| When the destination IP address (IPv4 or IPv6) is on a remote network, the destination MAC address will be the address of the | Host default gateway (router interface) |
| How are the IP addresses of the IP packets in a data flow associated with the MAC addresses on each link along the path to the destination for IPv4? | Address Resolution Protocol (ARP). |
| How are the IP addresses of the IP packets in a data flow associated with the MAC addresses on each link along the path to the destination for IPv6? | ICMPv6 Neighbor Discovery (ND). |
| 1. What destination MAC address would be included in a frame sent from a source device to a destination device on the same local network? | 1. When sending a frame to another device on the same local network, the device sending the frame will use the MAC address of the destination device. |
| 2. What destination MAC address would be included in a frame sent from a source device to a destination device on a remote local network? | 2. When sending a frame to another device on a remote network, the device sending the frame will use the MAC address of the local router interface, which is the default gateway. |
| 3. What two protocols are used to determine the MAC address of a known destination device IP address (IPv4 and IPv6)? | 3. Address Resolution Protocol (ARP) is used to determine the device MAC address of a known destination device IPv4 address. Neighbor Discovery (ND) is used to determine the MAC address of a known destination device IPv6 address. |
| When a device sends an Ethernet Layer 2 frame, it contains these two addresses: | • Destination MAC address - The Ethernet MAC address of the destination device on the same local network segment. If the destination host is on another network, then the destination address in the frame would be that of the default gateway (i.e., router). • Source MAC address - The MAC address of the Ethernet NIC on the source host. |
| To send a packet to another host on the same local IPv4 network, a host must know ? | the IPv4 address and the MAC address of the destination device. |
| How does the sending host know the IPv4 address? | are either known or resolved by device name |
| ow does the sending host know the MAC address on IPv4? | Must be discovered with ARP |
| What is the function of ARP | • Resolving IPv4 addresses to MAC addresses • Maintaining a table of IPv4 to MAC address mappings |
| ARP Table or ARP Cache | When a packet is sent to the data link layer to be encapsulated into an Ethernet frame, the device refers to a table in its memory to find the MAC address that is mapped to the IPv4 address. This table is stored temporarily in RAM memory |
| • If the packet’s destination IPv4 address is on the same network as the source IPv4 address, the device will | search the ARP table for the destination IPv4 address. |
| • If the destination IPv4 address is on a different network than the source IPv4 address, the device will | search the ARP table for the IPv4 address of the default gateway. |
| What is the binding of a IPv4 address with a MAC address called | Map |
| What is sent when a device needs to determine the MAC address that is associated with an IPv4 address, and it does not have an entry for the IPv4 address in its ARP table. | An ARP request |
| Where are ARP messages encapsulated | directly within the Ethernet Frame |
| Does ARP Messages have IPv4 headers | No |
| What header information is in the ARP Message ethernet frame. | • Destination MAC address – This is a broadcast address FF-FF-FF-FF-FF-FF requiring all Ethernet NICs on the LAN to accept and process the ARP request. • Source MAC address – This is MAC address of the sender of the ARP request. • Type - ARP messages have a type field of 0x806. This informs the receiving NIC that the data portion of the frame needs to be passed to the ARP process. |
| What does a Broadcast address look like. | FF-FF-FF-FF-FF-FF |
| What is in the type field for an ARP message | 0x806 |
| who will reply to ARP Request | Only the device with the target IPv4 address associated with the ARP request will respond with an ARP reply |
| What is encapsulated in the ethernet frame on an ARP Reply | • Destination MAC address – This is the MAC address of the sender of the ARP request. • Source MAC address – This is the MAC address of the sender of the ARP reply. • Type - ARP messages have a type field of 0x806. This informs the receiving NIC that the data portion of the frame needs to be passed to the ARP process. |
| What device will receive the reply of an ARP request. | Only the device that originally sent the ARP request will receive the unicast ARP reply. |
| What type of data communication is an ARP reply | Unicast |
| What type of data communication is an ARP request | Broadcast |
| What happens if there are no responses to an ARP request | the packet is dropped because a frame cannot be created. |
| Do static ARP table entries expire? | No |
| What happens when the time runs out on an ARP table entry | If a device does not receive a frame from a particular device before the timestamp expires, the entry for this device is removed from the ARP table. |
| What does IPv6 use in place of ARP | ICMPv6 Neighbor Discovery (ND) |
| What does ICMPv6 use to in place of Arp request and replies. | uses neighbor solicitation and neighbor advertisement messages, |
| Where is the IPv4 address of the default gateway stored | In the configuration of the hosts |
| show ip arp | command is used to display the ARP table |
| ARP spoofing | ARP poisoning attack. This is a technique used by a threat actor to reply to an ARP request for an IPv4 address that belongs to another device, such as the default gateway, as shown in the figure. The threat actor sends an ARP reply with its own MAC address. The receiver of the ARP reply will add the wrong MAC address to its ARP table and send these packets to the threat actor. |
| dynamic ARP inspection (DAI) | mitigation techniques |
| What do you need to match IPv6 addresses to MAC Addresses | Neighbor Discovery Protocol or ND |
| What does IPv6 use inplace of IPv4 route table / router cache | Neighbor cache |
| What does IPvt6use in place of the IPv4 ARP request | Neighbor solicitation message |
| How does IPv4 commuinicate the ARP request | Over the the Ethernet encapsulated in the Ethernet frame (does not use IPv4) |
| How does IPv4 commuinicate the ARP request | Using ICMPv6 which is then encapsulated in an IPv6 header an d then encapsulated in an Ethernet header and trailer |
| Whats included in the ICMPv6 neighbor solicitation header | target IPv6 address (Same as the IPv6 address as the packet on hold) |
| What are the steps in a Neighbor Solicitation | Neighbor Solicitation and Neighbor Advertisement messages are used for device-to-device messaging such as address resolution (similar to ARP for IPv4). Devices include both host computers and routers. |
| ICMPv6 ND uses ICMPv6 messages to perform what services? | Neighbor Solicitation messages Neighbor Advertisement messages Router Solicitation messages Router Advertisement messages Redirect Message |
| What are the steps in the Neighbor Advertisement messages | The Neighbor Advertisement message -Host C replies with an ICMPv6 neighbor advertisement message set as an ethernet unicast message directly to host A. -The ICMPv6 header includes Host C’s IPv6 address, and the associated MAC address that host A was requesting. -Host A receives the Ethernet frame, Examines the IPv6 address and the MAC address in the ICMPv6 header. -Host A adds it to its neighbor cache. -Host A can take the packet off hold -Host A updates the destination MAC address. |
| What are the steps in the Router Solicitation messages | 1. Host A has a packet to send to host C. 2. Destination address is on the same network as host A. 3. Host A checks the Neighbor cache for the destination IPv6 address. 4. NO MAC address associated with the IPv6 address. 5. IPv6 packet is placed on hold. 6. Host A creates an ICPMv6 neighbor solicitation message. (Like an IPv4 ARP request) 7. The ethernet NICs determine whether or not to accept and process the frame. Check notes |
| What are the steps in the Router Advertisement messages | Router Solicitation and Router Advertisement messages are for messaging between devices and routers. Typically router discovery is used for dynamic address allocation and stateless address autoconfiguration (SLAAC). |
| What are the steps in the Redirect Message | |
| What does link local mean? | In computer networking, a link-local address is a network address that is valid only for communications within the network segment or the broadcast domain that the host is connected to. |
| SLAAC | Stateless Address Auto-configuration for dynamic address allocation |
| 1. Which two ICMPv6 messages are used in SLAAC? | 1. The two ICMPv6 messages used in SLAAC are the router solicitation and the router advertisement. |
| 2. Which two ICMPv6 messages are used in to determine the MAC address of a known IPv6 address? | 2. The two ICMPv6 messages used in determining the MAC address of a known IPv6 address are the neighbor solicitation and the neighbor advertisement. |
| 3. To what type of address are ICMPv6 neighbor solicitation messages sent? | 3. ICMPv6 neighbor solicitation messages are sent as a multicast. |
| When does a device require the IPv6 Neighbor Discovery process? | When the destination MAC address is not known. This process is similar to ARP with IPv4. |
| How does IPv6 minimize the impact of the ND process on network hosts? | It uses a multicast address so that only a handful of addresses would be listening to the Neighbor Discovery messages. IPv6 creates a specially crafted multicast destination MAC address which includes a portion of the node address. |
| How does a router help to minimize the amount of IPv6 Neighbor Discovery traffic on a network? | The router keeps neighbor tables so that it doesn’t need to initiate ND for every destination host. |
| How does the Neighbor Discovery process differ when a destination host is on the same LAN and when it is on a remote LAN? | When a destination host is on the same LAN segment only the device that matches the IPv6 address responds and other devices drop the packet. When the device is remote the gateway device (usually a router) provides the MAC address of the interface on the local interface for the destination MAC and then searches for the MAC address on the remote network. The router will then place the responding IPv6/MAC address pair in the IPv6 Neighbor table. (similar to an ARP table in IPv4) |
| What does the Hub do with MAC addresses and IP addresses? | Nothing |
| Do the wireless Access Point do anything with the information given to it? | Yes. It repackaged it as wireless 802.11 frames. |
| What was the highest OSI layer that the Hub and Access Point used? | Layer 1 |
| When examining the PDU Details tab, which MAC address appeared first, the source or the destination? | Destination |
| Why in the PDU Details tab would the MAC addresses have the destination address first? | A switch can begin forwarding a frame to a known MAC address more quickly if the destination is listed first |
| Which router component holds the routing table, ARP cache, and running configuration file? | Ram Topic 9.2.0 - The routing table, ARP cache, and running configuration file are stored in volatile RAM. |
| What type of information is contained in an ARP table? | IPv4 address to MAC Address Maping Topic 9.2.0 - ARP tables are used to store mappings of IPv4 addresses to MAC addresses. When a network device needs to forward a packet, the device knows only the IPv4 address. To deliver the packet on an Ethernet network, a MAC address is needed. ARP resolves the MAC address and stores it in an ARP table. |
| A PC is configured to obtain an IPv4 address automatically from network 192.168.1.0/24. The network administrator issues the arp –a command and notices an entry of 192.168.1.255 ff-ff-ff-ff-ff-ff. Which statement describes this entry? | This is a static map entry Topic 9.2.0 - The IPv4 address of 192.168.1.255 on the 192.168.1.0/24 network is the broadcast address, which is statically mapped to ff-ff-ff-ff-ff-ff in the ARP table. |
| A cybersecurity analyst believes an attacker is spoofing the MAC address of the default gateway to perform a man-in-the-middle attack. Which command should the analyst use to view the MAC address a host is using to reach the default gateway? | arp -a Topic 9.2.0 - ARP is a protocol used with IPv4 to map a MAC address to an associated specific IP address. The command arp -a will display the MAC address table on a Windows PC. |
| Which two ICMPv6 messages are used during the Ethernet MAC address resolution process? (Choose two.) | Neighbor solicitation Neighbor advertisement Topic 9.3.0 - IPv6 uses neighbor solicitation (NS) and neighbor advertisement (NA) ICMPv6 messages for MAC address resolution. |
| How does the ARP process use an IPv4 address? | To determine the MAC address of a device on the same network Topic 9.1.0 - The ARP process is used to complete the necessary mapping of IPv4 and MAC addresses that are stored in the ARP table that is maintained by each node on a LAN. When the destination device is not on the same network as the source device, the MAC address of the Layer 3 device on the the source network is discovered and added to the ARP table of the source node. |
| Which action is taken by a Layer 2 switch when it receives a Layer 2 broadcast frame? | It sends the fame to all ports except the port on winch it received the frame Topic 9.2.0 - When a Layer 2 switch receives a frame with a broadcast destination address, it floods the frame to all ports except the port on which it received the frame. |
| What addresses are mapped by ARP? | IPv4 address to a destination MAC address Topic 9.2.0 - ARP, or the Address Resolution Protocol, works by mapping the IPv4 address to a destination MAC address. The host knows the destination IPv4 address and uses ARP to resolve the corresponding destination MAC address. |
| When an IPv4 packet is sent to a host on a remote network, what information is provided by ARP? | The MAC address of the router interface closest to the sending host |
| What will a Layer 2 switch do when the destination MAC address of a received frame is not in the MAC table? | It forwards the frame out of all ports excepts for the port at which the frame was received Topic 9.2.0 - A Layer 2 switch determines how to handle incoming frames by using its MAC address table. When an incoming frame contains a destination MAC address that is not in the table, the switch forwards the frame out all ports, except for the port on which it was received. |
| The ARP table in a switch maps which two types of address together? | Topic 9.2.0 - The switch ARP table keeps a mapping of Layer 2 MAC addresses to Layer 3 IP addresses. These mappings can be learned by the switch dynamically through ARP or statically through manual configuration. Layer 3 address to a layer 2 address |
| What is the purpose of ARP in an IPv4 network? | To obtain a specific MAC address when an IP address is known Topic 9.2.0 - ARP performs two functions: To obtain a specific MAC address when an IP address is known, by broadcasting an ARP request message to all devices on a particular Ethernet network To use the gathered information to create a viewable table of IP address to MAC address mappings |
| Which destination address is used in an ARP request frame? | FFFF.FFFF.FFFF.FFFF. Topic 9.2.0 - The purpose of an ARP request is to find the MAC address of the destination host on an Ethernet LAN. The ARP process sends a Layer 2 broadcast to all devices on the Ethernet LAN. The frame contains the IP address of the destination and the broadcast MAC address, FFFF.FFFF.FFFF. |
| What is one function of the ARP protocol? | Topic 9.2.0 - The two main functions of the ARP protocol are -to resolve an IPv4 address to a MAC address and -to maintain an ARP table, which lists the resolved pairs of IPv4 address and MAC address. A device automatically obtains an IP address through DHCP. The functions of DNS include resolving (or mapping) a domain name with its IP address and maintaining a table for the domain name/IP pairs. |
Created by:
jacobth