Juniper® JNCIA Exam Cram Notes : Network Tools

5. Operational Monitoring and Maintenance

5.3 Network tools

We can use a number network tools to help with troubleshooting and end-to-end connectivity. The ping, traceroute, ssh and telnet commands we use mostly. We would use ping to check end-to-end connectivity testing and we would use traceroute to check the path that we are using to get from one device to another, whether that is on our internal LAN or across the internet. With Junos if we are using a DNS name (i.e. google.co.uk), it will by default use IPv6 AAAA record to try and get find the host in question. If you don't have IPv6 configured on your network this is no help at all!

The ping destination command is a common troubleshooting tool used to check host reachability and network connectivity. It sends ICMP ECHO_REQUEST messages to elicit ICMP ECHO_ RESPONSE messages from the specified host.

We use 'set system services ping' command on our juniper devices to allow ping service. This command is written in configuration mode hierarchy.

Ping and traceroute are the network troubleshooting tools. We often use traceroute when the result of the ping command shows that end-to-end network connectivity is not established.

The 'deactivate system services telnet' command only deactivates the telnet service from our device. In order to remove the telnet service from our device, we use 'delete system services telnet'.

Traceroute command output is as shown below

images/QID238.JPG

After executing 'traceroute 192.168.5.1' command, the given output is obtained. We can determine the actual network path taken by the IP packets and also know where the problem might exist. The traceroute command lists all the routers that it passes through until the destination is reached, or fails to and is discarded.

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