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31 Cards in this Set
- Front
- Back
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07.ac
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The next 16 bits (07.ac) are the well-known HSRP ID. This part of the address was assigned by Cisco in the protocol, so it’s always easy to recognize that this address is for use with HSRP
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224.0.0.102
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GLBP - It also allows members of the group to communicate with each other through Hello messages sent every 3 seconds to the multicast address 224.0.0.102, User Datagram Protocol (UDP) port 3222.
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Active router
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by default, the active router directs the traffic from hosts to each successive router in the group.
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AVG
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Members of a GLBP group elect one gateway to be the active virtual gateway (AVG) for that group. Other group members provide backup for the AVG in the event that the AVG becomes unavailable. The AVG assigns a virtual MAC address to each member of the GLBP group. Each gateway assumes responsibility for forwarding packets sent to the virtual MAC address assigned to it by the AVG. These gateways are known as active virtual forwarders (AVFs) for their virtual MAC address. The AVG is responsible for answering Address Resolution Protocol (ARP) requests for the virtual IP address. Load sharing is achieved by the AVG replying to the ARP requests with different virtual MAC addresses.
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Fault tolerance
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First hop redundancy protocols (FHRP) are used to provide default gateway fault tolerance to hosts
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GLBP
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Gateway Load Balancing Protocol: A protocol offered by Cisco to help enterprises and service providers achieve and maintain high availability in network connections using redundancy and increased performance in the event of a network path failure
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How do you change the timers for HSRP? Why would you do it?
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(default) 3 seconds hello, 10 seconds for reply/deadYou would change this timer to reduce the time during a failover
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HSRP
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Hot Standby Router Protocol: A protocol that provides high network availability and nearly instantaneous hardware fail-over without administrator intervention. It generates a Hot Standby router group, including a lead router that lends its services to any packet being transferred to the Hot Standby address. If the lead router fails, it will be replaced by any of the other routers—the standby routers—that monitor it.
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Load-balancing
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The act of balancing packet load over multiple links to the same remote network.
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Logging
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Enable Syslog
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Logging trap VTY
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Send logs over the VTY line
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Logging trap warnings
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Logging warnings in SYSlog
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Multiple Forwarders
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GLBP supports up to 1,024 virtual routers as GLBP groups on each router’s physical interface and up to four virtual forwarders per group
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NetFlow 9
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(Cisco Proprietary) NetFlow allows the collection of flows of traffic on the network, including address and protocols in use. A recent version of NetFlow is version 9, referred to as Flexible NetFlow. End-to-end monitoring
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Preemption
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The HSRP preemption feature enables the router with highest priority to immediately become the Active router. Priority is determined first by the priority value that you configure, and then by the IP address. In each case a higher value is of greater priority.
When a higher priority router preempts a lower priority router, it sends a coup message. When a lower priority active router receives a coup message or hello message from a higher priority active router, it changes to the speak state and sends a resign message. |
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Show ip cache flow
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command provides a summary of the NetFlow statistics, including which protocols are in use.
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Show ip flow export
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To display the status and the statistics for NetFlow accounting data export, including the main cache and all other enabled caches, use the show ip flow export command in user EXEC or privileged EXEC mode.
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Show ip flow interface
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To verify NetFlow, you need to verify that the correct interfaces in the correct direction have been configured
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What is SNMP? |
SNMP is an (IEEE) Application layer protocol that provides a message format for agents on a variety of devices to communicate with network management stations
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SNMP (v1, v2c, v3)
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SNMPv1: Supports plaintext authentication with community strings and uses only UDP.
SNMPv2c: Supports plaintext authentication with MD5 or SHA with no encryption but provides GET BULK, which is a way to gather many types of information at once and minimize the number of GET requests. It offers a more detailed error message reporting method, but it’s not more secure than v1. It uses UDP even though it can be configured to use TCP. SNMPv3: Supports strong authentication with MD5 or SHA, providing confidentiality (encryption) and data integrity of messages via DES or DES-256 encryption between agents and managers. GET BULK is a supported feature of SNMPv3, and this version also uses TCP. |
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Standby router
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Even if the active router fails, the transition to the standby router will be transparent to the hosts because the virtual router, which is identified by the virtual IP and MAC addresses, is now used by the standby router. The hosts never change default gateway information, so traffic keeps flowing.
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Syslog V2
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Command to set syslog to version 2 to use enhanced features (if you have a syslog server)
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UDP
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User Datagram Protocol: A connectionless Transport layer protocol in the TCP/IP protocol stack that simply allows datagrams to be exchanged without acknowledgments or delivery guarantees, requiring other protocols to handle error processing and retransmission. UDP is defined in RFC 768
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UDP port 3222
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Hello messages sent every 3 seconds to the multicast address 224.0.0.102, User Datagram Protocol (UDP) port 3222
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UDP port 9996
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the Cisco default port number on which the NetFlow collectors listen for NetFlow packets
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Virtual MAC
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The virtual MAC address is the address that will be returned when an ARP request is sent by a host
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Virtual router
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As its name implies, the virtual router is not a physical entity. It really just defines the role that’s held by one of the physical routers. The physical router that communicates as the virtual router is the current active router. The virtual router is nothing more than a separate IP address and MAC address to which packets are sent.
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VLAN load balancing
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by using multiple VLANs and designating a specific router active for one VLAN, then an alternate router as active for the other VLAN via trunking
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VRRP
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Virtual Router Redundancy Protocol: A computer networking protocol that provides assignment of IP routers to participating hosts, which increases the availability and reliability of routing paths through automatic default gateway selections on a network
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What are the 0-7 Syslog message levels? How do you choose which one to use? |
Emergency (severity 0) - System is unusable.Alert (severity 1) - Immediate action is needed.
Critical (severity 2) - Critical condition. Error (severity 3) - Error condition. Warning (severity 4) - Warning condition.Notification (severity 5) - Normal but significant condition. Information (severity 6) - Normal information message. Debugging (severity 7) - Debugging message.Use it to limit the amount of messages sent to the syslog server, |
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What information can be gleaned from the command show log?
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This command displays the state of syslog error and event logging, including host addresses (and what level they’re running at), and which logging destinations (console, monitor, buffer, or host) logging is enabled. This command also displays Simple Network Management Protocol (SNMP) logging configuration parameters and protocol activity
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