May
17

DHCP – Dynamic Host Configuration Protocol

DHCP – Dynamic Host Configuration Protocol is a configuration protocol for the host’s set of connections on the IP networks. Obviously, computers within IP networks should be configured to communicate with each other. But some other information is needed to understand the mechanical of online communication such as IP (internet protocol) addresses, default routes and prefixes. DHCP protocol will let you to get rid of manual handling of certain tasks with a network administrator’s help. A central database should be connected to a network, if this protocol incorporated into it so the chances relating duplicating resource assignments can be eliminated. Read more…

May
09

Saving Router Configuration to Server

If you want to store a backup copy of your router’s configuration on a TFTP server we have a simple solution for you. This article will explain all the commands needed to save backup configuration of a device to TFTP server. All this for Cisco and also for Juniper device.

CISCO

You need to make regular backups of your router configuration files and keep copies in a safe place. If you have a serious failure that damages a router’s hardware or software, the configuration will be destroyed. And anybody who has had to reconstruct a complex router configuration file from memory will tell you how difficult and stressful this task is. But if you have a backup of the last working configuration file, you can usually get a router working again within minutes of fixing any hardware problems. Read more…

May
03

FTP – File Transfer Protocol

To get the general idea on the subject of FTP, it is important to be acquainted with the word protocol as a significant set of rules and conventions. The aim behind the protocols introduction intent was to make available communication (computer to computer) facilities. And well designed FTP is most suitable for this purpose and that’s why still in use. Though, it is on the screen since 1970s.

FTP is resided on the application layer of OSI standard model so particular tasks can be obtained with its use such as to uphold intercontinental communication and to produce standards relating online communication. File Transfer Protocol is well documented in the form of RFC 959. But all other related documents on the FTP technicality overviews are available at RFC sourcebook. The reliability of this protocol can be judged from that, it belongs to the oldest internet protocols family but can be implemented with the help of TCP protocol. Read more…

Apr
28

Configuring the Router via TFTP

If we want to load configuration commands via TFTP we can do this in very simple way and in this article we will se how to do it on Cisco and Juniper device.

CISCO

When we use TFTP to download set of configuration commands router do not echo each command which reduces the overhead and increases speed.

In our example, we configured the router by making it download the file called NewConfig from the server at 183.20.1.1 by using the Trivial File Transfer Protocol (TFTP). The router will copy the entire file via TFTP before entering the commands into the running configuration. This is extremely useful because sometimes some commands in the middle of a configuration could disrupt your access to the router, but the rest of the commands might fix the problem. If you tried to enter them manually using    TELNET    and    configure terminal, you would simply lock yourself out of the router and not be able to continue. A typical example of this problem happens when you replace an active access-list. When you enter the first line, the router puts an implicit    deny all    at the end, which could break your session. However, entering commands by using TFTP avoids this problem. Read more…

Apr
15

Gopher

The unique Gopher arrangements were taken as public in the year 1991 and you can view its depiction from the RFC 1436. This protocol was given the almost same name as of the sport’s team of Minnesota University, “Golden Gophers”.

The TCP/IP Application layer protocol “Gopher” was launched to share out, uncover, and to process documents online. Though initially, it was opened for communal as a smart option against WWW (World Wide Web) because of its menu documentation support, but in due course it remained completely futile to receive any popularity. The reason behind this infamy was that it offered some non maintainable, by the Web, features. According to one school of thought, the reason of this protocol’s collapse was its some degree of structure too and that was its non-flexibility especially when compared it to Hypertext Transfer Protocol or HTML, which is Gopher’s real competitor. Read more…

Apr
12

Administrative distance – Which route is the best?

Administrative distance is the measure used by Cisco routers to help them decide how to select the best path when there’s more that one route to the same destination from different routing protocols. We can say that in this manner administrative distance shows the real reliability of a routing protocol in one system. It shows which routes are more important based on the routing protocol from which they derived. Each routing protocol is prioritized in order of most to least reliable using an administrative distance value. Don’t get confused, a lower numerical value is preferred. For example, an EIGRP with an administrative distance of 90 will be chosen over a RIP route with an administrative distance of 120 and over OSPF route with an administrative distance of 110 to.

Here is a table with all default administrative distances used by Cisco routers: Read more…

Apr
11

Difference between Routed and Routing Protocols

Routed Protocols vs. Routing Protocols
RoutingIn this article we will cover the difference between Routed Protocols and Routing Protocols. This is one of the thing that can be asked of you if you are attending a job interview or if you are going to CCNA exam so, you must know the difference between a “routed” protocol and a “routing protocol” as one of the key concepts in the Routing world and networking world. Read more…

Apr
09

IMAP – Internet Message Access Protocol

Internet Message Access ProtocolIMAP – Internet Message Access Protocol is a means of getting the right of entry to an e-mail. This code of behavior is also suitable for accessing the bulletin board posts which are held in reserve on a mail server and that is perhaps communal. Additionally, that commonly well known mailing IMAP protocol is an Application layer protocol which is used to grant permission to an e-mail client to get reach to the e-mail that resides over a far flung e-mail server. Read more…

Apr
05

Saving VLAN.dat To NVRam

Saving VLAN.dat To NVRam - How to save VLAN.dat to different place – VLAN.dat redirection

Switch VLAN.dat managementSometimes it can happen to you that the VLAN Database is lost when the switch is restarted. This is especially often when working in the lab environment. To help cross this issue you can tell the switch to save the VLAN.dat file to NVRAM instead of storing it to Flash. By default on Cisco switches that are running Cisco IOS the Flash memory is a default place to store VLAN.dat Read more…

Mar
31

IRC – Internet Relay Chat Protocol

Internet Relay Chat protocol is introduced in order to use for chat. Online users can perform synchronized text messaging with its help. In point of fact, users involved in chatting are required to install software at both receiver and sender sides that will perform the functions of decoding and putting on view the data by means of the IRC protocol, for example Pidgin.

IRC - Internet Relay Chat Protocol Read more…

Mar
29

Firewall – Defending Networks

In network security today, a firewall may be a software or hardware that makes a barrier between our internal network and untrusted external network. You can look at the firewall as a set of related programs that enforce an access control policy between two or more networks.

firewallThe name “firewall” is very strange, it has been originally used to describe the segment that separated the engine compartment from the interior of an automobile. In the networking world firewall is the first line of defense and the technology that will allow us to segment the network in physically separate subnetworks. Read more…

Mar
19

Secure the switch – best steps

switch security Cisco devices have many features that are good for something but they can be easily exploited. You must know that the Internet is full of people that want to exploit your network for different or no reasons. We will show you the best ways for thinking ahead and securing the layer 2 of the network – the switches. Let’s start… Read more…

Mar
17

LDAP – Lightweight Directory Access Protocol

Lightweight Directory Access Protocol

The purpose of LDAP introduction was to supply a directory service offering protocol. That protocol is active on a layer, resting on top of the TCP/IP stack. Its mechanism is available for the connection, searching, and modification of the Internet directories. Actually, Lightweight Directory Access Protocol (a directory service) is consisted on the client-server representation. The main job of that protocol is to the facilitate right of entry to an accessible directory. Read more…

Mar
15

PVLAN configuration

Private VLAN – PVLAN configuration needs to be started by defining any secondary VLANs that are needed for isolation. Secondary VLAN  can be isolated or community VLAN.

Switch(config)# vlan 4
Switch(config-vlan)# private-vlan community
Switch(config)# vlan 5
Switch(config-vlan)# private-vlan community
Switch(config)# vlan 6
Switch(config-vlan)# private-vlan isolated

private VLAN - PVLAN configure Read more…

Mar
14

PVLAN – Private VLANs

Isolating Traffic inside a VLAN Using Private VLANs

In the article VACL – VLAN Access Lists we mention one way how to provide security on switch device like Cisco Catalyst switch. In this article we will see the other way of providing security with use of private VLANs – PVLAN.

private VLAN - PVLANThe whole idea is to make possible to group VLANs inside the VLANs. You see from the picture here on the right that this will give you the opportunity to make group od computers or servers inside main (primary) VLAN. It will be possible to have two servers in the VLAN 10 and both of them on the same subnet. Here it becomes little bit strange, then they can be separated into two Secondary VLANs, VLAN 4 and VLAN 5.

If you are interested in the PVLAN configuration: PVLAN configuration article 

Read more…

Mar
11

Netconf

A network proper running is an indispensable issue for the successful operations of that network. Today’s companies have become more and more reliant over the networking services. And the good performances of these services mean a business good quality management. In this regard, the network’s management fundamentals proffer you an easy to get outline of the network managing. That will not just cover the administration of a network itself but as well offer the coverage to those services running on that specific network.
Read more…

Mar
06

VACL – VLAN Access Lists

IP access control lists – ACLs are used by routers to deny or forward specific traffic from passing through some network interface. We can say that ACLs are used when traffic travels from one network address space to other. Cisco Catalyst switch can also have an ACL applied within a VLAN. This special kind of ACL is called a VLAN access control list - VACL. Read more…

Feb
28

SPAN – Switched Port Analyzer technology and configuration

In simple words SPAN technology enables port mirroring on selected switch.

In some cases you will need that some kind of server, PC or other network device receives a copy of network traffic that is destinated for some other device in the network. Why would you want that? Maybe you need some kind of control of the traffic or you want to implement IDS – Intrusion Detection System or something else. In that case you can configure every Cisco switch to send a copy of the traffic to one of the ports that is connected to sensor device. Read more…

Feb
23

Prevent ARP Spoofing using Dynamic ARP Inspection – DAI

Additional protection of potential man in the middle attack
Dynamic ARP Inspection will help us prevent Address Resolution Protocol – ARP spoofing attacks with help of DHCP functionality and specially DHCP snooping. This is why  Dynamic ARP Inspection is usually used simultaneously with DCHP snooping. Let’s se how is this technology protecting us from ARP attack. Read more…

Feb
22

Spoofing Attacks – ARP Spoofing

How attacker can launch man in the middle attack using ARP spoofing and what is ARP spoofing?
Attackers can attempt to launch an attack by sending gratuitous ARP – GARP replies. GARP reply messages are sent from some device in the network to other without the prior receiving of a request for sending a ARP reply. Is an ARP reply without cause. This reply without cause can tell network devices that the attacker’s MAC address corresponds to specific IP addresses that is actually IP address of some other device in the LAN. Read more…

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