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Labs 1 Setting up Cisco Packet Tracer 3 IPv4 Addressing 2 Initial Configuration on Cisco Router

Up 1.5 Compare TCP to UDP Transport Layer Protocols TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are the most prominent transport layer protocols. The transport layer (layer 4 of the OSI model) is responsible for creating and maintaining connections between two endpoints. Data payloads are encapsulated by the transport layer into segments with the necessary TCP or UDP header information. Once the payload is encapsulated by layer 4 it is then progressed to the network (layer 3) for further IP header addition. TCP and UDP are used by various applications where data needs to be moved across the internet or internal network. TCP is primarily used for applications that require reliable transmission of data, whereas UDP is used where some data loss is much less impactful (such as streaming a video or music). Ports A key component of the layer 4 transport protocols is the use of source and destination port numbers. These port numbers can identify an application or service, or be used dynamically by the client/server to identify TCP flows or communications between devices. The purpose of the port numbers are to ensure that the data reaches the destined application. For example, FTP (File Transfer Protocol) uses TCP/UDP port number 21. You can view a list of registered port numbers here: IANA Port Numbers . In total, there are 65535 ports that can be used. These port numbers are split into three groups, as below. Note that dynamic ports are also referred to as ephemeral ports. A user wants to access a website hosted on a webserver using HTTPS. In order for the webserver to know which application is required, destination port number 443 is used. The user's device will generate a random ephemeral source of say 59823. Any return traffic will have a destination port of 59823, and a source port of 443 from the webserver. Let's take a basic view of the layer 4 and 3 headers within a PDU (Protocol Data Unit) per the below for this HTTPS communication. TCP Header Below is a simplified view of a TCP header, found within an extract of a PDU (Protocol Data Unit). Each portion of the TCP header serves a purpose, read more below. TCP Handshakes (Start and Finish) Because TCP is a connection oriented protocol, handshakes are required to bring the connection stream up before data can be transmitted. To begin a connection, a 3-way handshake is used while a 4-way handshake is used to end the connection. See below: UDP Header The UDP header is much smaller and a smaller feature set as compared to TCP, due to it being a connectionless transport protocol. The total size of a UDP header is 8 bytes. TCP vs. UDP There are many differences between TCP and UDP of which the key ones are outlined below.

Up 1.4 Identify interface and cable issues (collisions, errors, mismatch duplex, and/or speed) Collisions Collisions were only a real problem in previous generation Ethernet networks, where shared media forced the use of primarily half-duplex. This meant that only one device within the collision domain could transmit at a time. Collisions afflicted bus and hub networks, and the use of CSMA/CD was required to improve network stability and performance. In modern networks, as each port on a switch is it's own collision domain with full-duplex, collisions are close to impossible. Collision detection is disabled on a full-duplex interface. Identifying Collisions on a Cisco Appliance To identify a collision the most used command is "sh interfaces [Interface Number] ". Specifically we are looking for the CRC (Cyclic Redundancy Check), frame and collision counters within the output. Lets look at an example below: Errors Network errors beyond collisions are still very much an issue that can cause service degradation or outages. Using the "sh interfaces " command we can quickly check if any issues are due to an incrementing error counter. When investigating a network issue or outage, the error counters are a very useful tool in determining the possible cause. For example, a high CRC count could indicate a duplex mismatch, or high overruns may indicate that the appliance hardware specifications do not fit the use criteria. Lets review a "sh interfaces " output to see what each counter in bold means using the below example: CLI outputs in bold font like this will have an explanation just below. The below output is same as the screenshot above in the Collisions section of this page. NbRTR1#sh interfaces GigabitEthernet0/1 GigabitEthernet0/1 is administratively down, line protocol is down (disabled) Shows the status of the line, in this case it is manually in a shutdown state. Hardware is CN Gigabit Ethernet, address is 00d0.bc33.c602 (bia 00d0.bc33.c602) ​ MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, MTU denotes the maximum packet size, BW is bandwidth and DLY is the transmission delay. reliability 255/255, txload 1/255, rxload 1/255 Reliability shows how the interface is performing, higher is better. txload and rxload shows how congested the interface is. Updated every 5 minutes. Encapsulation ARPA, loopback not set Keepalive set (10 sec) ​ Full-duplex, 100Mb/s, media type is RJ45 This outlines the current duplex and speed setting, including the transmission media inserted into the interface. This should match the other device. output flow-control is unsupported, input flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00, Last input 00:00:08, output 00:00:05, output hang never Last clearing of "show interface" counters never ​ Input queue: 0/75/0 (size/max/drops); Total output drops: 0 Queueing strategy: fifo Output queue :0/40 (size/max) Here the output shows the current Quality of Service type and packet queuing methodology. fifo stands for First in - First out. In this instance there is no evidence that the buffer is full causing packets to be dropped. ​ 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec These two counters show the total bit rate of incoming and outgoing packets, including the number of packets per second. This output gives a good overall picture of network use. 0 packets input, 0 bytes, 0 no buffer Packets Input - the total number of error free packets. Bytes - the total (including encapsulation data) amount of traffic received. No buffer - the number of packets discarded due to no buffer space available. Received 0 broadcasts, 0 runts, 0 giants, 0 throttles Runts - packets that are smaller than 64 bytes, which are typically dropped. Giants - packets that are larger than 1518 bytes in size. Throttles - the count of times that the receiver is disabled due to low hardware resource. ​ 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort Input Errors - the total sum of all erroneous incoming packets. CRC - checksum generated by the remote end, which if the checksum does not match it indicates a collision and is counted. Frame - the number of packets with failed CRC, indicating collisions. Overrun - the number of times that packets were dropped due to hardware constraints (input rate to high) Ignored - the count of packets dropped due to further interface buffers being low on resource ​ 0 watchdog, 1017 multicast, 0 pause input Watchdog - Count of packets where the watchdog receive timer expired. Pause Input - A pause frame tells the sender of traffic to wait until the remote side's buffers are empty. Can be seen during high usage beyond the hardware capabilities. 0 input packets with dribble condition detected Dribble Condition - This is where the packet is slightly too big, but is still accepted. 0 packets output, 0 bytes, 0 underruns Packets Output - Total number of packets sent by the appliance. Bytes - Total amount of data sent including encapsulation bytes. Underruns - Number of times the transmission has been faster that the router can handle. 0 output errors, 0 collisions, 1 interface resets Output Errors - Sum of all erroneous packets sent by the appliance. Collisions - Total number of messages transmitted due to a collision. Interface Resets - This is the total number of times where an interface has been reset due to an issue, admin shut down or loop detection. 0 unknown protocol drops This is where drops are recorded of which are of unknown cause. 0 babbles, 0 late collision, 0 deferred Babbles - Counted when packets larger than 1518 bytes are sent. Late Collisions - This counter can increment when collisions occur after transmitting the preamble. Deferred - This increases when the hardware had to defer a frame when ready to transmit due to carrier assertion. 0 lost carrier, 0 no carrier Lost Carrier - Number of times that the carrier was lost during transmission. No Carrier - Number of times the carrier was not available. 0 output buffer failures, 0 output buffers swapped out Output buffer failures - Number of times the buffer failed. Output buffers swapped out - When the outbound buffer is full, packets are stored in DRAM until buffer is available. Duplex Mismatch/Interface Speed Mismatch ​ What is Duplex? In it's simplest form, describing a link's duplex setting covers whether data can be sent and received at the same time, or if one way transmission only is available. There are three different types: In order for the link to work optimally, both sides of the transmission media need to be configured with the same settings. This is generally configured to be "Auto" or "Hard-set". When configuring an interface to Auto, the two appliances will negotiate the duplex settings. Hard-setting the duplex values needs to be done on both sides. If the duplex setting differs then collisions and errors will occur, and end user impact will be seen. Configuring Duplex If the devices cannot negotiate which duplex option to use, then hard-setting will be required on both sides. In modern Ethernet networks you will typically use Full-Duplex. The following commands will hard-set to the interface ("duplex ?" is included to show the options available): NbRTR1#conf t Enter configuration commands, one per line. End with CNTL/Z. NbRTR1(config)#interface gi0/1 NbRTR1(config-if)#duplex ? auto Enable AUTO duplex configuration full Force full duplex operation half Force half-duplex operation NbRTR1(config-if)#duplex full NbRTR1(config-if)#exit NbRTR1(config)#exit NbRTR1# ​ Verify that the command was accepted by using the "sh running-config " command and finding the interface. You could also run "sh run int gi0/1 ". NbRTR1#sh run interface GigabitEthernet0/1 no ip address duplex full <<<<<<<<<<<<<<<< speed auto ​ Interface Speed Like with duplex, interface speeds also need to be negotiated or hard set, as interface capabilities differ between devices. Speed is the maximum throughput available on that link. An incorrectly configured speed setting which has mismatched on the appliances will cause dropped packets and errors. Interface speed capabilities are typically understood by their naming convention: Ethernet - 10Mbps FastEthernet - 100Mbps GigabitEthernet - 1000Mbps So for example, if the interface on router1 has FastEthernet ports, and the interfaces on router2 are GigabitEthernet, then the maximum speed available will be 100Mbps. ​ Configuring Speed To manually configure the bandwidth available on the link, we can use the command "speed [10/100/1000/auto] ", like below: ​ NbRTR1#conf t Enter configuration commands, one per line. End with CNTL/Z. NbRTR1(config)#interface Gi0/1 NbRTR1(config-if)#speed ? 10 Force 10 Mbps operation 100 Force 100 Mbps operation 1000 Force 1000 Mbps operation auto Enable AUTO speed configuration NbRTR1(config-if)#speed 100 NbRTR1(config-if)#exit NbRTR1(config)#exit NbRTR1# ​ To verify we will be using the "sh run" command and locate the interface configuration. ​ NbRTR1#sh run interface GigabitEthernet0/1 no ip address duplex full speed 100 <<<<<<<<<<<<<<<<

Jargon Buster - Z Zones --- ...

Jargon Buster - L LAN Local Area Network ... Latency --- ... Layer --- ... Load Balance --- ... Loss/Lossy --- ... LLDP Link Layer Discovery Protocol ... Leased Line --- ... Link Layer --- ... Loopback Address --- ...

Jargon Buster - T TCP Transmission Control Protocol ... Throughput --- ... TTL Time To Live ... Transport Layer --- ... Trunk --- ... TFTP Trivial File Transfer Protocol ... Toggling --- ... TCP/IP Model Transmission Control Protocol/Internet Protocol Model ... Topology --- ... Tiered Network --- ... Tagging --- ... Time Out --- ...

Jargon Buster - O OSPF Open Shortest Path First ... OS Operating System ... Overutilisation --- ... OEM Original Equipment Manufacturer ... OSI Model Open Systems Interconnection Model ...

Jargon Buster - N Network --- ... Node --- ... Native VLAN --- ... NIC Network Interface Card ... NNI Network to Network Interface ... NTP Network Time Protocol ... Next Hop --- ... NS Name Server ... Neighbour --- ... Network Layer --- ... Noise --- ...

Jargon Buster - Y nothing here yet :)

Jargon Buster - P Port (Physical) --- ... Ping --- ... Packet --- ... Protocol --- ... Port (TCP/UDP) --- ... Policy --- ... Path Cost --- ... Peer --- ... PPP Point to Point Protocol ... Port SPAN Switched Port Analyser ... Provider --- ...

Jargon Buster - V VLAN --- ... Virtual Round Trip Time ... VDOM Virtual Domain ... VLSM Variable Length Subnet Masking ... VTP Remote Desktop Protocol ... VOIP Request for Comments ... VPN Virtual Private Network ... VRF Virtual Forwarding and Routing ...

Jargon Buster - W WLAN Wireless Local Area Network ... Wireless Network --- ... WPA Wireless Protected Access ... Wi-Fi Wireless Fidelity ... WEP Wired Equivalent Privacy ... WAN Wide Area Network ...