Troubleshooting ip Chapter 5e

objectives Upon completion of this chapter, you should be able to: Find IP configuration settings on Windows & Linux Troubleshoot IP configuration problems Use the ipconfig command prompt command Tell if a host is using APIPA Identify the difference between netstat and nbtstat Use the tracert command to find problesm in routing

Troubleshooting ip configuration issues 5.8.1 Troubleshooting ip configuration issues

What’s wrong here? 192.168.2.4 is on a different network than the rest.

What’s wrong here? Nothing. This is a Class A. The 3 host octets can be anything with a default SM.

What’s wrong here? WE ARE USING SUBNET-ZERO (THE FIRST TOTAL RANGE) Magic # in 3rd octet is: 4 Ranges: 172.17.0.0 172.17.3.255 2) 172.17.4.0 Therefore, 172.17.4.127/22 is in a different range than the rest.

What’s wrong here? Host A is connected to the LAN, but it can’t get access to the Internet. What’s the problem? /27 (.224)= 11100000; magic # is 32. Ranges: 32-63, 64-95, etc. The host & the DG are in different subnets.

What’s wrong here? You can’t ping www.google.com but you can ping an IP address. DNS couldn’t translate the name to the IP address. What should you check?

What’s wrong here? APIPA. The 3 169.254 hosts can communicate with each other but not the file server nor the Internet/any other network.

Rouge dhcp server Common situations: Install a server OS on virtual machine for testing & you accidently activate DHCP Mobile hotspot enabled on phone & DHCP server is enabled on it Some hosts may get an IP from the rouge DHCP server & not be able to communicate

5.8.2 Using ipconfig

Viewing ip info

Viewing ip info with ipconfig IP address, SM DG Ipconfig /all Lots more

Statically assign ip

Let it go… and get a new one Ipconfig /release Let’s go of a DHCP assigned address Ipconfig /renew Gets a new IP address from DHCP

Review- q

Using ifconfig on linux 5.8.3 Using ifconfig on linux

ifconfig Works pretty much like ipconfig but on Linux As a standard user, you can view IP info As a super user, you can modify the IP info Review TestOut 5.8.3

activity TestOut Lab 5.8.5- Explore IP Configuration TestOut Lab 5.8.6- Troubleshoot IP Configuration Problems 1 TestOut Lab 5.8.7- Troubleshoot IP Configuration Problems 2 TestOut Lab 5.8.8- Troubleshoot IP Configuration Problems 3 TestOut Lab 5.8.9- Troubleshoot IP Configuration Problems 4 TestOut 5.8.10- Practice Questions (5)

Troubleshooting ip communications 5.9 Troubleshooting ip communications

Use ping to test Tests connectivity Echo request/echo reply Can’t get to a website? Try and ping it. Success= site is up/DNS problem Fail= other problem/site down Echo request/echo reply Try ping destination first, then close to far

Use tracert to test Shows the path the packet takes Can identify exactly where problem is Windows- tracert www.cisco.com Linux- traceroute www.cisco.com Measures hops (going through a router) Any * timed out * may mean the router ignores the ICMP traceroute traffic Example Next Slide

Tracert example

Arp test Views ARP table (IP-MAC) Arp –a Arp –d (in administrator mode) allows you to manually remove an entry Arp –s allows you to manually input an entry

netstat Displays detailed info about how your computer is communicating with other computers or network devices Info/statistics about the network interfaces, active connections, ports, etc. Netstat, netstat –a Netstat: displays only a list of ACTIVE connections Netstat –a: list of ALL connections AND ports listening (Good for seeing open ports, possibly some rogue stuff coming in) If you maintain a web server, for example, and it seems to be slow to respond, you could run a netstat to see the established connections, ports being used, traffic stats, etc.

activity 5.9.1- Network Communication Troubleshooting 5.9.2- Using Ping & Tracert 5.9.4/5.9.5- Using arp, netstat 5.9.6- LAB 5.9.7- Practice Questions

Troubleshooting name resolution 5.10 Troubleshooting name resolution

activity 5.10.1- Name Resolution Troubleshooting 5.10.2- Fact Sheet (Review) 5.10.3- Using nslookup 5.10.4- LAB 5.10.5- Practice Questions

Troubleshooting ip Chapter 5e