CISCO : What You Make Possible

Troubleshooting Link Issues in various CISCO switch

Network Administrator or network engineer will facing with the link issues. This blog will give you direction or how to troubleshoot with using the right command or possible command to tackle the issue.

Link Issue : Port Status and Counters

2900#sh int gig 1/0/1  ( this command will show you the port/interface status.)

GigabitEthernet1/0/1 is down, line protocol is down (notconnect)
Hardware is Gigabit Ethernet, address is 70ca.9b2d.9f81 (bia 70ca.9b2d.9f81)
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Auto-duplex, Auto-speed, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

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Understand OSI Layer & TCP/IP Protocol

What is OSI Layer (The Open Systems Interconnection model) : 

Conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization (ISO), maintained by the identification ISO/IEC 7498-1.

Its seven-layered approach to data transmission divides the many operations up into specific related groups of actions at each layer.

OSI Model

Source : Clean-clouds-OSI Model

             Wikipedia-OSI Model

Each OSI layer have a specific protocol or task for doing the communication is called TCP/IP

What  is TCP/IP ( Transmission Control Protocol (TCP) and the Internet Protocol (IP) ) :

The Internet protocol suite is the networking model and a set of communications protocols used for the Internet and similar networks. It is commonly known as TCP/IP, because its most important protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP), were the first networking protocols defined in this standard. It is occasionally known as the DoD model, because the development of the networking model was funded by DARPA, an agency of the United States Department of Defense.
TCP/IP provides end-to-end connectivity specifying how data should be formatted, addressed, transmitted, routed and received at the destination. This functionality has been organized into four abstraction layers which are used to sort all related protocols according to the scope of networking involved.[1][2] From lowest to highest, the layers are the link layer, containing communication technologies for a single network segment (link), the internet layer, connecting independent networks, thus establishing internetworking, the transport layer handling process-to-process communication, and the application layer, which interfaces to the user and provides support services.

TCP/IP Model

OSI vs TCP/IP

Source : tcpipguide-TCP/IP model
              coffeeshop.macinfotechnologies-TCP/IP model
             electronicdesign.com-Difference-between-osi-seven-layer-network-model-and-tcpip
             vlsm-calc.net-OSI&TCP/IPmodels

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Clos Network : When old become Favorite

Clos Network History :

Created in the mid-1950s as a method to switch telephone calls. Multistage circuit switching network, first formalized by Charles Clos in 1952.  Charles Clos was a researcher at Bell Laboratories in the 1950s. He published a paper titled "A Study of Non-blocking Switching Networks" in the Bell System Technical Journal in 1953.

Source 1 : Clos Network-Wikipedia
Source 2 : Clos Network-NetwrokWorld


Example Clos Design : 

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