A Linux kernel vulnerability affecting version 4.9 and up could allow an attacker to carry out denial-of-service attacks on a system with an available open port, according to an Aug 6 security advisory from the CERT Coordination Center at Carnegie Mellon University’s Software Engineering Institute. “Linux kernel versions 4.9+ can be forced to make very expensive […]
I have seen some people want to make shared folder between VirtualBox and ubuntu but it is sometimes tricky for them to make a shared folder: 1- First install “Insert guest Additional CD” from Devices. In ubuntu VM, you may install those sh files first. 2- restart the system 3- Make a Shared Folder from […]
Sometimes it is necessary to have policy and separate your Vlan like below diagram. In this diagram, WWW and FTP server have communication together, so we put in community. On the other hand, SQL server shouldn’t be seen by FTP or WWW server, so, we put on isolated. In fact, there are three types of […]
1-STP(Spanning-Tree Protocol) (802.1D) To prevent loop between switches, Cisco uses Spanning-Tree protocol. STP is the simplest and oldest protocol which is enable by default in Cisco devices. STP is a industry standard which is used by other vendors to prevent loops in devices. STP uses BPDU(bridge protocol data unit) to detect loops in devices. If […]
NetFlow is a networking analysis protocol that gives the ability to collect detailed information about network traffic as it flows through a router interface. NetFlow helps network administrators answers the questions of who (users), what (application), when (time of day), where (source and destination IP addresses) and how network traffic is flowing. Enter a caption […]
1-SPAN(Switched Port Analyzer Network) To sniff or to analyse traffic on specific port or Vlan you can use SPAN. As it is shown in Figure 1, we want to have traffic of FastEthernet0/1 on port FastEthernet0/10. So, simple we can define monitor session for interface FastEthernet0/1 as a source and FastEthernet0/10 as a destination. Figure […]
1- What is SNMP? SNMP is an application-layer protocol that provides a message format for communication between managers and agents. The SNMP system consists of: an SNMP manager, an SNMP agent, and a MIB. The SNMP agent contains MIB variables whose values the SNMP manager can request or change. A manager can get a value […]
TACACS+ and Radius is a security application that provides centralized validation of users attempting to gain access to a router or network access server. In Table 1 main difference between TACACS and Radius are mentioned: Feature TACACS+ RADIUS Encryption Packet fully encrypted Password encrypted Protocol TCP UDP Standard Cisco Industry AAA Separate AAA Combine AAA […]
1- Understanding HSRP HSRP is the Cisco standard method of providing high network availability by providing first-hop redundancy for IP hosts on an IEEE 802 LAN configured with a default gateway IP address. HSRP allows two or more HSRP-configured routers to use the MAC address and IP network address of a virtual router. The virtual […]
Tunneling provides a mechanism to transport packets of one protocol within another protocol. The protocol that is carried is called as the passenger protocol, and the protocol that is used for carrying the passenger protocol is called as the transport protocol. Generic Routing Encapsulation (GRE) is one of the available tunneling mechanisms which uses IP […]
EtherChannel is a port link aggregation technology or port-channel architecture used primarily on Cisco switches. It allows grouping of several physical Ethernet links to create one logical Ethernet link for the purpose of providing fault-tolerance and high-speed links between switches, routers and servers(wiki). Enter a caption for this image (optional) There are two protocols in […]