Connectivity Troubleshooting

Today, played a little catch with Rowan, the went to a new coffee shop in Shreveport called MOOR Coffee Co (they have a good cappuccino but the shop has a kids playroom adjacent - which can be a little noisy)

Troubleshooting

• ICMP: Internet Control Message Protocol (PING) 
• sends out an Echo Repay testing two-way connectivity
• Use the Extended Ping option if you need to send out the ping from a different IP interface than the exit IP interface on a router
• Traceroute (TR): this using PING and utilizes the TTL field
• Time To Live is a mechanism to minimize network loops by setting the maximum of hops a patch can travel
1. TR sends the first PING with a TTL of 1 and the first hop will reduce the TTL to 0, then drop the packet, and send back a "time exceeded" reply. 
2. TR then sends the second PING with a TTL of 2 and the second hop does the same as the first hop.
3. This continues and builds a visual route the patch is taking until the PING gets to its final destination.
4. NOTE: to abort the TR press Ctrl-Shift-6
• Layer 1 - Other tools
• Show ip interface brief
• Show interface
• Layer 2
• show arp
• show mac address-table 
• Layer 4
• Telnet - telnet to a destination ip address with the port number to see if it answers
• Other Tools - to test DNS
• nslookup
• Ping by FQDN  (ping www.cisco.com)

Cisco IP SLA

• is an active traffic monitory feature of IOS to measure network performance
• it can generate traffic that mimics normal production traffic to report performance characteristics such as latency, jitter, and loss
• R1(config)#ip sla 1    (you can set up multiple)
• R1(config-ip-sla)#icmp-echo 10.1.2.10   (set the destination address)
• R1(config-ip-sla-echo)#frequency 10   (every 10 seconds)
• R1(config-ip-sla-echo)#exit
• R1(config)#ip sla schedule 1 life forever start-time now
•      
• R1#show ip sla statistics  (view anytime or send to reporting server)