What are the STP times?

 Hello Timer  Forward delay Timer  Max-age Timer   Hello Timer: How often switches send BPDU’s by default every 2 seconds Forward delay Timer: how much long a port must spend time in both learning and listening state. By default 15 seconds Max-age Timer: How long a switch will retain BPDU information from a neighbor switch [...]

Why we use Spanning Tree Protocol in the Switches?

 Broadcast Storms Duplicate Frame copies Unstable MAC Table   Broadcast Storms Without any loop removing mechanism, switches will flood broadcasts endlessly throughout the network. This is known as broadcast storm. Duplicate Frame copies A device could receive duplicate copies of same frame from different switches. It creates additional overhead on the network. Unstable MAC Table [...]

A receiving host computes the checksum on a frame and determines that the frame is damaged. The frame is then discarded. At which OSI layer did this happen?

The Data Link layer provides the physical transmission of the data and handles error notification, network topology, and flow control. The Data Link layer formats the message into pieces, each called a data frame, and adds a customized header containing the hardware destination and source address. Protocols Data Unit (PDU) on Datalink layer is called [...]

What is BFD?

Bidirectional Forwarding Detection (BFD) provides a low-overhead, short-duration method of detecting failures in the forwarding path between two adjacent routers, including the interfaces, data links, and forwarding planes. BFD is a detection protocol that you enable at the interface and routing protocol levels. Cisco supports the BFD asynchronous mode, which depends on the sending of [...]

How DHCP works?

The Dynamic Host Configuration Protocol (DHCP) is a standardized network protocol used on Internet Protocol (IP) networks. The DHCP protocol is controlled by a DHCP server that dynamically distributes network configuration parameters, such as IP addresses, for interfaces and services. A router or a residential gateway can be enabled to act as a DHCP server. [...]

What is UDLD?

Unidirectional Link Detection (UDLD) is a data link (layer 2) protocol from Cisco Systems to monitor the physical configuration of the cables and detect unidirectional links. UDLD allow two switches to verify if they can both send and receive data on a point-to-point connection.UDLD works with the Layer 1 (L1) mechanisms to determine the physical [...]

What is ICMP?

ICMP is Internet Control Message Protocol, a network layer protocol of the TCP/IP suite used by hosts and gateways to send notification of datagram problems back to the sender. It uses the echo test / reply to test whether a destination is reachable and responding. It also handles both control and error messages.

What is VPN?

A VPN (Virtual Private Network) is a way of making a secure connection to and from a network or computer. VPNs have been used for years, but they have become more powerful in recent years. They are more affordable and also much faster. There are many different types of VPNs available. Let’s take a look [...]

What is VDC’s?

Cisco Nexus 7000 Series switches can be segmented into virtual devices based on customer requirements. VDCs offer several benefits e.g. fault isolation, administration plane, separation of data traffic, and enhanced security. This logical separation provides the following  benefits: Administrative and management separation Change and failure domain isolation from other VDCs Address, VLAN, VRF, and vPC isolation Each VDC acts as an [...]

What is WCCP?

WCCP (Web Cache Communication Protocol) allows Cisco IOS routing platforms to transparently redirect content requests. The main benefit of transparent redirection is that users need not configure their browsers to use a web proxy. Instead, they can use the target URL to request content, and have their requests automatically redirected to a cache engine. The [...]

How does TCP try to avoid network meltdown?

TCP includes several mechanisms that attempt to sustain good data transfer rates while avoiding placing excessive load on the network. -TCP’s “Slow Start”, “Congestion Avoidance”, “Fast Retransmit” and “Fast Recovery” -TCP also mandates an algorithm that avoids “Silly Window Syndrome” (SWS), an undesirable condition that results in very small chunks of data being transferred between [...]

What is WCCP?

Web Cache Communication Protocol (WCCP) is a Cisco proprietary content-routing protocol that provides a mechanism to redirect traffic flows in real-time. It has built-in load balancing, scaling, fault tolerance, and service-assurance (failsafe) mechanisms. WCCP allows utilization of Cisco Cache Engines(ACNS/WAAS) to localize web traffic patterns in the network, enabling content requests to be fulfilled locally. [...]