Building a small network
Verify Connectivity with Traceroute
-A trace returns a list of hops as a packet is routed through a network. It could be used to identify the point along the path where the problem can be found. -requests to the next hop timed out as indicated by the asterisk (*)
Duplex Mismatch Issues
-If one of the two connected devices is operating in full-duplex and the other is operating in half-duplex, a duplex mismatch occurs. While data communication will occur through a link with a duplex mismatch, link performance will be very poor. -Duplex mismatches are typically caused by a misconfigured interface or in rare instances by a failed autonegotiation. Duplex mismatches may be difficult to troubleshoot as the communication between devices still occurs.
What do network protocols define?
1. Processes on either end of a communication session 3. Types of messages 4. Syntax of the messages 5. Meaning of informational fields 6 .How messages are sent and the expected response 7. Interaction with the next lower layer
IP Addressing for a Small Network
Devices that will factor into the IP addressing scheme include the following: 1. End user devices - The number and type of connection (i.e., wired, wireless, remote access) 2. Servers and peripherals devices (e.g., printers and security cameras) 3. Intermediary devices including switches and access points -------------- The use of a planned IP addressing scheme makes it easier to identify a type of device and to troubleshoot problems, as for instance, when troubleshooting network traffic issues with a protocol analyzer. To identify all switches in a network policy, the administrator could specify the summarized network address 192.168.x.4/30. - aka network address
IOS Ping Indicators
Exclamation Mark (!): -Exclamation mark indicates successful receipt of an echo reply message. -It validates a Layer 3 connection between source and destination. Period ( . ): -A period means that time expired waiting for an echo reply message. -This indicates a connectivity problem occurred somewhere along the path. Uppercase U: -indicates a router along the path responded with an ICMP Type 3 "destination unreachable" error message. -Possible reasons include the router does not know the direction to the destination network or it could not find the host on the destination network.
Google/Cisco DNS Servers
Googles: IPv4 addresses: 8.8.8.8 or 8.8.4.4 IPv6 address: 2001:4860:4860::8888 -Cisco offers OpenDNS which provides secure DNS service by filtering phishing and some malware sites. You can change your DNS address to Cisco DNS Addresses: 208.67.222.222 and 208.67.220.220
Voice and Video Applications
Infrastructure -The network infrastructure must support the real-time applications. -Existing devices and cabling must be tested and validated. -Newer networking products may be required. VoIP -VoIP devices convert analog telephone signals into digital IP packets. -Typically, VOIP is less expensive than an IP telephony solution, but the quality of communications does not meet the same standards. -Small network voice and video over IP can be solved using Skype and non-enterprise versions of Cisco WebEx. IP Telephony -An IP phone performs voice-to-IP conversion with the use of a dedicated server for call control and signaling. -Many vendors provide small business IP telephony solutions such as the Cisco Business Edition 4000 Series products. Real-Time Applications -The network must support quality of service (QoS) mechanisms to minimize latency issues for real-time streaming applications. -Real-Time Transport Protocol (RTP) and Real-Time Transport Control Protocol (RTCP) are two protocols that support this requirement.
Extended Traceroute
Like the extended ping command, there is also an extended traceroute command. -It allows the administrator to adjust parameters related to the command operation. -This is helpful in locating the problem when troubleshooting routing loops, determining the exact next-hop router, or determining where packets are getting dropped or denied by a router or firewall. -traceroute and then enter for more parameters -The Cisco IOS extended traceroute option enables the user to create a special type of trace by adjusting parameters related to the command operation.
6 Troubleshooting Process
Step 1. Identify the Problem -This is the first step in the troubleshooting process. -Although tools can be used in this step, a conversation with the user is often very helpful. Step 2. Establish a Theory of Probable Causes -After the problem is identified, try to establish a theory of probable causes. -This step often yields more than a few probable causes to the problem. Step 3. Test the Theory to Determine Cause -Based on the probable causes, test your theories to determine which one is the cause of the problem. -A technician will often apply a quick procedure to test and see if it solves the problem. -If a quick procedure does not correct the problem, you might need to research the problem further to establish the exact cause. Step 4. Establish a Plan of Action and Implement the Solution -After you have determined the exact cause of the problem, establish a plan of action to resolve the problem and implement the solution. Step 5. Verify Solution and Implement Preventive Measures -After you have corrected the problem, verify full functionality. -If applicable, implement preventive measures. Step 6. Document Findings, Actions, and Outcomes -In the final step of the troubleshooting process, document your findings, actions, and outcomes. -This is very important for future reference.
Small Network Growth
To scale a network, several elements are required: 1. Network documentation - Physical and logical topology 2. Device inventory - List of devices that use or comprise the network 3. Budget - Itemized IT budget, including fiscal year equipment purchasing budget 4. Traffic analysis - Protocols, applications, and services and their respective traffic requirements should be documented -The Windows 10 Data Usage tool is especially useful to determine which applications are using network services on a host. The Data Usage tool is accessed using Settings > Network & Internet > Data usage > network interface (from the last 30 days).
Network Baseline
-Creating an effective network performance baseline is accomplished over a period of time. -Measuring performance at varying times and loads will assist in creating a better picture of overall network performance. -The output derived from network commands contributes data to the network baseline. -One method for starting a baseline is to copy and paste the results from an executed ping, trace, or other relevant commands into a text file. -Among items to consider are error messages and the response times from host to host. If there is a considerable increase in response times, there may be a latency issue to address. -For example you ping network devices in January, February, March, and April and record the command output. Come April you see that the average round trip time is much higher than it was in February-March - this can indicate a network issue is arising and needs investigated. -Another example is if you pinged an address in the morning and then in the evening and the avg round trip time is much higher at the evening this could indicate network trouble. -Corporate networks should have extensive baselines; more extensive than we can describe in this course. Professional-grade software tools are available for storing and maintaining baseline information. -Cisco's best practices for baseline processes can be found by searching the internet for "Baseline Process Best Practices".
Redundancy in a Small Network
-In order to maintain a high degree of reliability, redundancy is required in the network design. Redundancy helps to eliminate single points of failure. -There are many ways to accomplish redundancy in a network. Redundancy can be accomplished by installing duplicate equipment, but it can also be accomplished by supplying duplicate network links for critical areas, as shown in the figure. -Small networks typically provide a single exit point toward the internet via one or more default gateways. If the router fails, the entire network loses connectivity to the internet. For this reason, it may be advisable for a small business to pay for a second service provider as backup.
Extended Ping
-The Cisco IOS offers an "extended" mode of the ping command. This mode enables the user to create special type of pings by adjusting parameters related to the command operation. -Extended ping is entered in privileged EXEC mode by typing ping without a destination IP address. You will then be given several prompts to -The ping ipv6 command is used for IPv6 extended pings.
Traffic Management
-The routers and switches in a small network should be configured to support real-time traffic, such as voice and video, in an appropriate manner relative to other data traffic. -In fact, a good network design will implement quality of service (QoS) to classify traffic carefully according to priority during times of congestion, as shown in the figure.
ICMP Message Types
0- Echo Reply 3- Destination Unreachable 4- Source Quench 5- Redirect 8- Echo Request 9- Router Advertisement 10- Router Solicitation 11- Time Exceeded 12- Parameter Problem 13- Timestamp Request 14- Timestamp Reply 17- Address Mask Request 18- Address Mask Reply
Device Selection for a Small Network
Cost The cost of a switch or router is determined by its capacity and features. This includes the number and types of ports available and the backplane speed. Other factors that influence the cost are network management capabilities, embedded security technologies, and optional advanced switching technologies. The expense of cable runs required to connect every device on the network must also be considered. Another key element affecting cost considerations is the amount of redundancy to incorporate into the network. Speed and Types of Ports/Interfaces Choosing the number and type of ports on a router or switch is a critical decision. Newer computers have built-in 1 Gbps NICs. Some servers may even have 10 Gbps ports. Although it is more expensive, choosing Layer 2 devices that can accommodate increased speeds allows the network to evolve without replacing central devices. Expandability Networking devices are available in fixed and modular physical configurations. Fixed configuration devices have a specific number and type of ports or interfaces and cannot be expanded. Modular devices have expansion slots to add new modules as requirements evolve. Switches are available with additional ports for high-speed uplinks. Routers can be used to connect different types of networks. Care must be taken to select the appropriate modules and interfaces for the specific media. Operating System Features and Services Network devices must have operating systems that can support the organizations requirements such as the following: 1. Layer 3 switching 2. Network Address Translation (NAT) 3. Dynamic Host Configuration Protocol (DHCP) 4. Security 5. Quality of service (QoS) 6. Voice over IP (VoIP)
Common Protocols Per Device
Web Server -Web clients and web servers exchange web traffic using the Hypertext Transfer Protocol (HTTP). -Hypertext Transfer Protocol Secure (HTTPS) is used for secure web communication. Email Server -Email servers and clients use Simple Mail Transfer Protocol (SMTP) to send emails. -Email clients use Post Office Protocol (POP3) or Internet Message Access Protocol (IMAP) to retrieve email. -Recipients are specified using the [email protected] format. FTP Server -File Transfer Protocol (FTP) service allows files to be downloaded and uploaded between a client and FTP server. -FTP Secure (FTPS) and Secure FTP (SFTP) are used to secure FTP file exchange. DHCP Server -Dynamic Host Configuration Protocol (DHCP) is used by clients to acquire an IP configuration (i.e., IP address, subnet mask, default gateway and more) from a DHCP server. DNS Server -Domain Name Service (DNS) resolves a domain name to an IP address (e.g., cisco.com = 72.163.4.185) -DNS provides the IP address of a web site (i.e., domain name) to a requesting host.
