What is Multi VLAN port ?

The multi-VLAN port is a feature which allows switch for configuring a single port for two or more vlans. This feature allows users from different VLANs to access a server or router without implementing InterVLAN routing capability. A multi-VLAN port performs normal switching functions in all its assigned VLANs. Multi-VLAN port will not work when [...]
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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 [...]
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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 [...]
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SNMP

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 [...]
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How ARP works?

ARP stands for Address Resolution Protocol. When you try to ping an IP address on your local network, say 192.168.1.1, your system has to turn the IP address 192.168.1.1 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 [...]
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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 [...]
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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 [...]
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SPAN

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.  

How to configure Site-to-Site VPN on Cisco ASA?

Access-Lists Add the ACLs which we will need to NAT, the encryption domain and the group policy. access-list Example_Policy_ACL extended permit tcp object-group Local_LAN object-group Remote_LAN eq 80 access-list Example_Policy_ACL extended deny ip any any access-list Example_VPN_ACL permit ip object-group Local_LAN object-group Remote_LAN Group Policy Create your group policy which will restrict traffic between hosts [...]
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How packet flow in Palo Alto Firewall?

Basic: Initial Packet Processing —-> Security Pre-Policy —-> Application —-> Security Policy —-> Post Policy Processing Advance: Initial Packet Processing —-> Source Zone/Source Address —-> Forward Lookup —-> Destination Zone/Destination Address —-> NAT policy evaluated   Security Pre-Policy —-> Check Allowed Ports —-> Session Created   Application —-> Check for Encrypted Traffic —-> Decryption Policy —-> Application Override Policy —-> Application ID [...]
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How packet flows in Checkpoint firewall?

Checkpoint process the packet in the ingress and the egress using two CHAINS. Basic: -Physical layer – ingress interface -Data Link Layer/Ethernet -Inspect Driver [inspect Engine] -Network Layer/IP Routing -Inspect Driver -Data Link Layer/Ethernet -Physical layer – egress interface Advance: 1. NIC hardware -The network card receives electrical signalling from the link partner. 2. NIC [...]
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How to configure QoS on Cisco ASA firewall

There are three steps for configuring the QoS on Cisco ASA firewall 1.Identify the traffic or define the traffic classes. To identify the traffic first create a new access-list to match the traffic. Once access-list is created call it in the class-map ciscoasa(config)#access-list qos extended permit tcp any any eq 25 ciscoasa(config)#class-map qos ciscoasa(config-cmap)#match access-list [...]
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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 [...]
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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 [...]
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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 [...]
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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 [...]
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Etherchannel

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 [...]
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