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In: Cisco, DHCP
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DHCP, Dynamic Host Configuration Protocol  is the protocol used by network devices like a PC or a printer (DHCP clients) to obtain IP Address, Default Gateway, Domain Name, DNS Servers, NetBIOS servers and more that helps the device to work properly in an IP Network. While in an ideal scenario, most if not all organisations run the DHCP server on  a Windows server or a Linux/Unix server. While this is justfiable in bigger corporate and enterprise networks, a smaller network like a branch office can be supported by a local Router, Switch or a Firewall can run a DHCP server without the need of anRead More →

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In: Cisco
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NAT, Network Address Translation in simple terms translates an IP address into another. Network Address Translation is of different types like Static NAT (One to One) Dynamic NAT (Many to Many) Overloading (Many to One) We will focus on Overloading form of NAT. This is called as Port Address Translation (PAT) or even Network Address Port Translation (NAPT). NAT Overloading translates many private IP addresses from a Local Area Network (LAN) onto a single registered legal Public IP address. Here, the source IP and the source port gets translated to the Public IP and a different source port. Typical network configuration would be on anRead More →

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In: OpenSource Router
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XORP pronounced as "Zorp" is eXtensible Open Router Platform. XORP is an extensible open source routing platform released under a BSD style License. While designed for extensibility, XORP provides a fully featured platform that implements IPv4 and IPv6 routing protocols and a unified platform to configure them. Vyatta Opensource router implements XORP routing platform. XORP is the only open source platform to offer integrated multicast capability. XORP's modular architecture allows rapid introduction of new protocols, features and functionality, including support for custom hardware and software forwarding.Read More →

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In: Cisco, Secure Shell(SSH)
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Using Telnet for remote administration of Cisco Routers and Switches (infact for any other device like a unix,linux or a solaris seerver) is not very secure as the data including the passwords are sent in clear text. It will only be a matter of time for a malicous attacker who can sniff the packets to gain access to the passwords and infact the whole network. It is recommended that Secure Shell (SSH) is used for remote administration of Cisco Routers and Switches.  NOTE: Cisco IOS on the Catalyst switches are by default supplied with the SSH feature bultin. However, the basic Cisco IOS for theRead More →

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In: Networking
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ICMP Redirect is a type 5 ICMP error message sent by a gateway router to a sending host informing of an optimal alternate route to the destination host and to update its routing table with the new host route to the target destination host. The router forwards the original packet to the next hop router or to the destination host and sends the ICMP Redirect message to the sending host so that the subsequent packets to the destination host can be sent via the new route.Read More →

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In: Cisco, Security
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Cisco Port Security is a features that can help secure access to the physical network. Any Network admins nightmare is an unauthorised device or a PC connecting to the network. This could be as simple as an innocent guest plugging his PC into a floor port hoping to get an internet connection or a malicious intruder connecting to the network trying to gain access to confidential information. Consequences could as bad as Virus, Spyware or malware infection from a PC unprotected PC A malicious hacker or an intruder gaining access to the network A malicous attacker launching a Denial of Service attack using MAC Address floodingRead More →

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In: Cisco, DHCP, Networking, Windows
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A DHCP server is the one which provides a network client with a unique IP address, Subnet mask, Gateway and DNS server IP address automatically when it connects to the network. A DHCP Relay Agent is a computer, server or a Router in a particular subnet which receives a DHCP client broadcast and relays it to a DHCP server in another network or a subnet. A DHCP Relay Agent is more a helper agent here that gets the client a DHCP lease.Read More →