When transmitting data packets breaks up into frame. Data link layer attached its own PDU during transmission and de-attached the PDU during reception of data. Data link layer is not related to these PDU in any way. These headers contain the information of port address and IP address.
Ccna Determine Ip And Header Information For A Data Packet Mac Addresses AreTopologyPart 1: Record a PC’s IP C onfiguration InformationPart 2: Use Wireshark to Capture DNS Queries and ResponsesPart 3: Analyze Captured DNS or UDP Packets Background / ScenarioWhen you use the internet, you use the Domain Name System (DNS). Also defining that how can data format and also give IP address to that data.Answers Note : Red font color or g ray highlights indicate text that appears in the instructor copy only. When R1 gets that information, the router removes the Layer 2 header and creates a new one for the type of network the data will be placed onto (the serial link).Data link layer Mac Addresses are used to identify which hardware is the. The source MAC address will be the MAC address of PC1 and the destination MAC address will be that of G0/0 on R1. When Router A receives the packet it strips off the ethernet header, decrements the TTL and looks up the destination IP in the routing table to determine where.Lab – Using Wireshark to Examine a UDP DNS Capture (Answers Version)Because PC1 connects to an Ethernet network, an Ethernet header is used. Data link layer work on MAC.![]() At the terminal prompt, enter cat /etc/resolv.conf to determine the DNS ~]$ cat /etc/resolv.conf If you do not have an IP address on your local network, run the following command in the ~]$ sudo lab.support.files/scripts/configure_as_dhcp.shConfiguring the NIC to request IP info via DHCP…Note: In Part 1, your results will vary depending on your local area network settings and internet ~]$ ifconfigInet 192.168.8.10 netmask 255.255.255.0 broadcast 192.168.8.255Inet6 fe80::a00:27ff:fe82:75df prefixlen 64 scopeid 0x20Ether 08:00:27:82:75:df txqueuelen 1000 (Ethernet)RX packets 41953 bytes 14354223 (13.6 MiB)TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 Enter ifconfig at the prompt to display interface information. Open a terminal in the VM. To check your network settings go to: Machine > Settings, select Network, the tab Adapter 1, Attached to: Bridged Adapter. Your CyberOps Workstation VM network settings should be set to bridged adapter. ![]() In the terminal window, type ping as an alternative to the web browser. Click Apply.Note : If you do not see any results after the DNS filter was applied, close the web browser. In the Wireshark main window, type dns in the Filter field. Click Stop to stop the Wireshark capture when you see Google’s home page.Part 3: Analyze Captured DNS or UDP PacketsIn Part 3, you will examine the UDP packets that were generated when communicating with a DNS server for the IP addresses for Step 1: Filter DNS packets. In the Wireshark window, select and double-click enp0s3 from the interface list. In the Internet Protocol Version 4 line, the IP packet Wireshark capture indicates that the source IP address of this DNS query is 192.168.8.10 and the destination IP address is 8.8.4.4. The destination MAC address is from the default gateway because this is the last stop before this query exits the local network.Is the source MAC address the same as the one recorded from Part 1 for the VM? The source MAC address is from your VM because your VM originated the DNS query. The Ethernet II line displays the source and destination MAC addresses. This is the number of bytes it took to send a DNS query to a named server requesting the IP addresses of If you used a different web address, such as the byte count might be different. In the first line in the packet details pane, frame 429 had 74 bytes of data on the wire. Each field in a UDP header is only 16 bits as depicted below.Click the arrow next to User Datagram Protocol to view the details. A UDP header only has four fields: source port, destination port, length, and checksum. The UDP segment contains the DNS query as the data. The length of the UDP segment in your example may be different. DNS servers listen on port 53 for DNS queries from clients.In this example, the length of the UDP segment is 40 bytes. Port 53 is a well-known port reserved for use with DNS. The destination port is 53. The source port was randomly generated by the VM using port numbers that are not reserved. The source port number in this example is 58029. Cisco anyconnect secure mobility client for macIn this example: 74 bytesAnswers may vary. Record your Wireshark results in the table below:Answers may vary. Any data transfer reliability issues that occur must be handled by the application layer.Expand as necessary to see the details. The 32 bytes of DNS query data is in the following illustration in the packet bytes pane (lower section) of the Wireshark main window.The checksum is used to determine the integrity of the UDP header after it has traversed the internet.The UDP header has low overhead because UDP does not have fields that are associated with the three-way handshake in TCP. The other 32 bytes are used by DNS query data. In this example, frame 488 is the corresponding DNS response packet. Step 3: Examine the fields in a DNS response packet.In this step, you will examine the DNS response packet and verify that the DNS response packet also uses the UDP. In this example: 8.8.4.4Is the source IP address the same as the local PC’s IP address you recorded in Part 1?Is the destination IP address the same as the default gateway noted in Part 1?No, the default gateway is 192.168.8.1 and the DNS server is 8.8.4.4. In this example: 192.168.8.10Answers may vary. In this example: 00:78:cd:01:f6:50Answers may vary. Notice the source and destination IP addresses in the IP packet.The a nswer will vary. In the Ethernet II frame for the DNS response, what device is the source MAC address and what device is the destination MAC address?The source MAC address is the default gateway and the destination MAC address is the VM. This is because the DNS response packet will include a variety of information about the domain. It is a larger packet compared to the DNS query packet.
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