This discussion aims to provide a new experience on how to analyze and solve troubleshooting on a computer network or the internet. In addition, we also need some supporting software such as Linux Fedora Core 5 OS, Windows XP and Fedora Core 5 Repository.
Network Troubleshooting
Before practicing, it is better if we first understand the basic theory of network troubleshooting. So what points do we need to understand?
Beginner Class:
- Services related to DNS, DHCP, Routing, Internet Access, Email and Proxy.
- TCP/IP Network Protocols, Subnetting and Nating.
Advanced Class:
- Complex networks using switching (multilayer)
- OSI model (physical layer - transport)
1. ipconfig
It is a tool to display the network configuration used by a computer. Administrator or User. First we check to make sure that the configuration entered (manually) or obtained from the DHCP server is valid. what we need to do is open cmd and try the following options:
- ipconfig
- ipconfig/all
- ipconfig/release
- ipconfig/renew
Trial ipconfig
2. ping
It is a tool to test or check connections using the ICMP protocol. Generally, administrators use this tool to identify symptoms that arise, making it easier to perform corrective action. So please try the following options:
- ping ip gateway
- ping ipdnsserver
- ping -t server ip
Ping test
Some messages that may appear if pinging is unsuccessful include:
- TTL Expired in Transit: means the number of hops (routers) passed through to communicate with the server has exceeded the TTL (Time To Live), use ping --i to define the TTL when pinging.
- Destination Host Unreachable: means that the packet sent was unable to reach its destination, usually caused by an incorrect routing table on the default gateway machine, or the router/hop above it.
- Request Timed Out: means the echo replay message cannot be received again within the specified time. Usually this message appears because of a blockade that may be done by a firewall (either on the router side or on the target side).
- Ping request could not find host: means that the resolving domain server on our PC cannot translate to an IP address. Usually this is caused by the DNS client setting being wrong or our communication with the DNS server being disrupted/disconnected.
3. nslookup
It is a tool used to diagnose DNS server services, perform queries to map a domain to an IP address or vice versa. The nslookup tool can also be used to find out the mx (mail server) or ns (nameserver) responsible for a domain. Practiced options:
- nslookup ugm.ac.id
- nslookup (enter) then set query=mx or set query=ns
Trial nslookup
4. tracert
It is an abbreviation of traceroute, which is a tool to display the path or routing of communication packets between our computer and another computer (server). This tool will display the number of hops (routers) passed through when heading to the target server. Options used:
- tracert ipserver/domain
- tracert -d ipserver/domain
Trial tracert
5. pathping
It is a tool on windows that is used to measure network latency and network loss (in percentage) at a certain hop between the source address and the destination address. The options used: pathping -n ipserver/domain.
Trial pathing
6. Netstat
Netstat stands for network status, used for various purposes, including displaying routing tables, displaying services running on Windows, displaying communication protocol ports that are currently occurring. Practiced options:
- netstat -rn
- netstat --an
Netstat Trial
Summary
The most common Network Troubleshooting on Windows Internet Connection Lost, what to do? Here are some steps as a guide:
Step 1
Check the lights on the Ethernet and Ethernet cable:
- If there is no sign of connection, check the cable.
- Also check the lights on the hub/switch including the power.
Step 2
Make sure that your IP, DNS and default settings are configured correctly.
- use ipconfig, ipconfig/all to check.
- use ipconfig/release, ipconfig/renew for networks using dhcp.
Step 3
Ping Default Gateway, the default gateway IP can be seen via the ipconfig command
Step 4
Ping DNS and proxy server (if network policy requires using proxy)
Step 5
If everything works, ping and tracert to ipserverdns and ipserverproxy
Step 6
If everything works, try pinging and tracert to external sites such as www.google.com
Also read Network Troubleshooting in Linux , that's all.