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The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite. It is used by network devices, like routers, to send error messages and operational information.   ICMP TYPE NUMBERS   The Internet Control Message Protocol (ICMP) has many messages that are identified by a "type" field. Type      Name                                                                    Reference ----         -------------------------                      ---------   0            Echo Reply                                                          [RFC792]   1            Unassigned                                                            [JBP]   2            Unassigned                                                            [JBP]   3            Destination Unreachable                                       [RFC792]   4            Source Quench                                                     [RFC792]   5            Redirect  

          CCNA  200-120 solved Dumps If you are planning to get CCNA Routing and Switching certification ,you must take 200-120 exam. download CCNA 200-120 dumps pdf and practice the real exam questions. CCNA 200-120 exam is the composite exam associated with the Cisco CCNA Routing and Switching certification. CCNA 200-120 exam tests a candidate’s knowledge and skills required to install, operate, and troubleshoot a small to medium size enterprise branch network.  The topics include all the areas covered under ICND 1 and ICND2 Exams. What Are Dumps Exactly? Also known as braindumps, they are basically questions and answers taken straight from the copyrighted exams.  During the CCNA exam, you will be asked to answer 50 multiple choice questions and 3 lab questions. The dumps are usually complied by previous test takers who somehow remember the questions by memory, by the people who run the Test Centers, or by the actual exam creators. Whether they are tech

A micro-burst occurs when a specific amount of data (in bytes) is exceeded in a given time interval. Micro-Burst Monitoring Overview The micro-burst monitoring feature allows you to monitor traffic on a per-port basis for both ingress and egress ports and to detect unexpected data bursts within a very small time window (micro-seconds). This allows you to detect flows in the network that are at risk of data loss, and that may require extra bandwidth. The micro-burst monitoring feature allows you to specify these limits as absolute values (for data and burst size) or as a percentage of the link speed. When these thresholds are exceeded the system generates a Syslog alarm message. How to Use Micro-Burst Monitoring The micro-burst monitoring feature monitors bursts in real time. The monitoring process also provides an overview of data path issues, and is helpful in identifying potential capacity issues in a network. Syslog messages are generated with the burst exceeds th

Asymmetric routing Asymmetric routing is when a packet takes one path to the destination and takes another path when returning to the source. For example, review the following diagram. Packets from client to server take one route and packets from server to client take another route. ROUTERA----->WAN LINK 1----->ROUTERB  Going  path. ROUTERB----->WAN LINK 2 ----->ROUTERA  Return path. Related topics-  Unicast flooding  Out-of-order packets

                                      Out of order packets out-of-order delivery is the delivery of data packets in a different order from which they were sent. Out-of-order delivery can be caused by packets following multiple paths through a network, or via parallel processing paths within network equipment that are not designed to ensure that packet ordering is preserved. One of the functions of TCP is to prevent the out-of-order delivery of data, either by reassembling packets into order or forcing retries of out-of-order packets. IP protocol by nature does not guarantee packet delivery in the order in which they were sent, this is a common behavior since we can’t control the entire path of a packet when traversing different carrier’s networks/Paths. In principle, applications that use a transport protocol such as TCP or SCTP [Stream control transmition protocol ]   don't have to worry about packet reordering, because the transport protocol is responsible for reassembl

                                               Unicast flooding It refers to the unintentional behavior of a switch treating a unicast packet as a broadcast packet; The cause of flooding is that the destination MAC address of the packet is not in the L2 forwarding table of the switch. Normally occurs when the router needs to deliver a packet; it has an ARP entry for a destination host, but the switch has no CAM entry.   The result is a packet that needs to be flooded to all of the ports in the VLAN In order to locate that MAC address port/VLAN. Common reasons for destination MAC address not being known to the switch: Cause 1: Asymmetric Routing. With asymmetric routing, transmit and receive packets follow different paths between a host and the peer with which it communicates, at some point in the packet delivery path a Switch may not have that MAC address destination on its CAM table and would need to flood the frame in order to discover which port/MAC address is.

What are the Port Roles in RSTP? 1. Root port - It is the port on the switch that has the best root path cost to the root bridge. This is identical to 802.1D. 2. Designated port - The switch port on a network segment that has the best root path cost to the root. 3. Alternate port - A port that has an alternative path to the root, different from the path the root port takes. This path is less desirable than that of the root port. 4. Backup port - A port that provides a redundant (but less desirable) connection to a segment where another switch port already connects. If that common segment is lost, the switch might or might not have a path back to the root. What are different port states in RSTP? 1. Discarding - Incoming frames simply are dropped; no MAC addresses are learned.This state combines the 802.1D Disabled, Blocking, and Listening states. 2. Learning - Incoming frames are dropped, but MAC addresses are learned. 3. Forwarding - Incoming frames are forwa

What is STP & Redundant Links? Spanning Tree Protocol (STP) is a protocol which prevents layer 2 loops. STP enables switches to become aware of each other so that they can negotiate a Loop-Free path through network. In practical Scenario, Redundant links are created to avoid complete network failure in an event of failure of one link. How STP works? STP chooses a Reference point (Root Bridge) in the network and calculates all the redundant paths to that reference point. Than it picks one path by which to forward frames and blocks other redundant paths. What are the different port states? 1. Disabled - A port in the disabled state does not participate in the STP. 2. Blocking - A blocked port does not forward frames. It only listens to BPDUs. The purpose of the blocking state is to prevent the use of looped paths. 3. Listening - A port in listening state prepares to forward data frames without populating the MAC address table. The port also sends and listens t

Explain Border Gateway Protocol (BGP) ? Border Gateway Protocol advertises, learns and chooses the best paths inside the global Internet. When two ISPs connect, they typically use BGP to exchange routing information. Enterprises also sometimes uses BGP to exchange routing information with ISPs, allowing the Enterprise routers to learn Internet routes. when we have multiple Internet connections and we want to influence some packets to take one path and some packets to take another we use BGP. Can Routers on different subnet become BGP neighbors? BGP does not require neighbors to be attached to the same subnet. Instead, BGP routers use a TCP connection between the routers to pass BGP messages allowing neighboring routers to be on the same or different subnet. What TCP port number BGP use for connection? BGP uses TCP port 179 for the connection. Difference between eBGP and iBGP neighbor? In iBGP, neighborship is formed between routers within the same AS (autonom