IP address and Subnetting

IP ADDRESS & SUBNETTING Private IP addressing – Subnet Mask calculation – If the CIDR value is /25 then subnet mask will be – In binary – 11111111.11111111.11111111.10000000  (8+8+8+1 = 25) Same way if subnet mask is – the CIDR value will be /18 (8+8+2) Wild card calculation – Whatever the subnet mask [...]

OSI layer in short with example

7. Application layer-Responsible for initiating or services the request. e.g SMTP, DNS, HTTP, and Telnet 6. Presentation layer-Formats the information so that it is understood by the receiving system e.g Compression and encryption depending on the implementation 5. Session layer– Responsible for establishing, managing, and terminating the session e.g NetBIOS 4. Transport layer-Breaks information into [...]

Important CLI commands for F5 LTM

TMOS commands run util bash -enable shell show sys self-ip -show self IP’s show ltm persistence persist-records -show persistence records list ltm node [node_address] -show node status modify ltm node [node_address] down -disable node modify ltm node [node_address] up -enable node modify net packet-filter all logging enabled -enable logging for all packet filters delete ltm [...]


Vlan trunking -Vlan divides the broadcast domain -In New switch, Default Vlan = Native Vlan = Vlan 1 -Native Vlan can be changed from Vlan 1 to Vlan10, 20 etc. -Vlan 1 cannot be deleted even after entering command -Vlan 1 carries critical traffic like CDP, VTP etc. -Access port carries traffic of only one [...]

Cisco ASA troubleshooting commands

AAA debug radius debug tacacs show aaa-server protocol PROTOCOL_NAME test aaa-server Access Control Lists show access-list show run | include ACCESS_LIST_NAME show run object-group show run time-range Application Inspection show conn state STATE_TYPE detail show service-policy Configuring Interfaces show firewall show int show int ip brief show ip show mode show nameif show run interface [...]

What is the use of default route?

In computer networking, the default route is a setting on a computer that defines the packet forwarding rule to use when no specific route can be determined for a given Internet Protocol (IP) destination address. All packets for destinations not established in the routing table are sent via the default route. The default route generally [...]


Simple Network Management Protocol (SNMP) is an application–layer protocol defined by the Internet Architecture Board (IAB) in RFC1157 for exchanging management information between network devices. It is a part of Transmission Control Protocol⁄Internet Protocol (TCP⁄IP) protocol suite. SNMP is one of the widely accepted protocols to manage and monitor network elements. Most of the professional–grade [...]

How ARP works?

ARP stands for Address Resolution Protocol. When you try to ping an IP address on your local network, say, your system has to turn the IP address into a MAC address. This involves using ARP to resolve the address, hence its name. Systems keep an ARP look-up table where they store information about [...]

How Load balancer works?

A load balancer is a device that acts as a reverse proxy and distributes network or application traffic across a number of servers. Load balancers are used to increase capacity (concurrent users) and reliability of applications. They improve the overall performance of applications by decreasing the burden on servers associated with managing and maintaining application and [...]

TCP- Three way handshake

The Three-way handshake begins with the initiator sending a TCP segment with the SYN control bit flag set. TCP allows one side to establish a connection. The other side may either accept the connection or refuse it. If we consider this from application layer point of view, the side that is establishing the connection is [...]


The SPAN feature, which is sometimes called port mirroring or port monitoring, selects network traffic for analysis by a network analyzer. The network analyzer can be a Cisco SwitchProbe device or other Remote Monitoring (RMON) probe.  

Cisco ASA firewall common troubleshooting commands part 1

Check the system status myfirewall/pri/act# show firewall Firewall mode: Router myfirewall/pri/act# show version Cisco Adaptive Security Appliance Software Version 9.1(1) Device Manager Version 7.1(1)52 Compiled on Wed 28-Nov-12 10:38 by builders System image file is “disk0:/asa911-k8.bin” Config file at boot was “startup-config” myfirewall up 218 days 1 hour failover cluster up 5 years 10 days [...]

Palo Alto-CLI cheat sheet

Device management: Show general system-health information –> show system info Show percent usage of disk partitions –> show system disk-space Show the maximum log file size –> show system logdb-quota Show running processes –> show system software status Show processes running in the management plane –> show system resources Show resource utilization in the dataplane [...]

Checkpoint firewall common commands part 2

For basic firewall informaton gathering: fgate stat-Status and statistics of Flood-Gate-1. fwaccel <stat|stats|conns> – View status, statistics or connection table of SecureXL. fw getifs-Show list of configured interfaces with IP and netmask. cpstat <app_flag> [-f flavour] -View OS, HW and CP application status. Issue cpstat without any options to see all possible application flags <app_flag> and [...]

common Switch troubleshooting commands

For CPU related issues: Show process cpu sorted Show process cpu history Show platform port-asic stats drop Show controllers cpu-interface Debug platform cpu-queues Show plat for ip For memory issues Show memory statistics Show process memory sorted Show buffers For link issues Show interface status | inc connected Test cable-diagnostics tdr interface <> Show cable-diagnostic [...]


There are three types of Etherchannels negotiation mechanism PAgP  (Port Aggregation Protocol)- Cisco’s proprietary negotiation protocol LACP (Link Aggregation Protocol)  – Standards-based negotiation protocol Static Persistence (“On”) – No negotiation protocol is used   There are two types of Etherchannels 1) Layer2   2) Layer3 1) Layer2 Etherchannels: Switch1(config)# interface range gigabitethernet0/1 -4  Switch1(config-if-range)# switchport access [...]

PVST+ & RPVST+ configuration

spanning-tree mode {pvst | rapid-pvst} ##Bridge priority## spanning-tree vlan 1-4094 priority 32768 ##STP Timers, in seconds## spanning-tree vlan 1-4094 hello-time 2 spanning-tree vlan 1-4094 forward-time 15 spanning-tree vlan 1-4094 max-age 20 ##PVST+ Enhancements## spanning-tree backbonefast spanning-tree uplinkfast ##Interface attributes ## interface FastEthernet0/1 spanning-tree [vlan 1-4094] port-priority 128 spanning-tree [vlan 1-4094] cost 19 ##Manual link type [...]