ELN DAY 2 Flashcards
is a Layer 2 Cisco proprietary protocol that gathers information about neighboring (attached) Cisco devices. Since CDP is a Layer 2 protocol and does not require any IP addresses to be assigned, successful communication does not indicate routing (a Layer 3 function) is configured. CDP data is used to develop network maps by analyzing the CDP packets.
Cisco Discovery Protocol (CDP)
how often a device transmits CDP packets.
CDP timer
how long a device stores CDP information it receives from neighboring devices.
CDP holdtime
Layer 2 devices used to define collision domains with independent bandwidth on each port. Although collision domains are defined with a switch, broadcast domains are not.
switches
Three Functions of a Switch
address learning, making forward/filter decisions, and loop avoidance.
automatically monitor links between all bridges(switches) in a network to prevent network loops. It is required in a network comprised of Layer 2devices if redundant links are used for backup purposes.
Spanning Tree Protocol (STP)
sent every two seconds to detect changes and dynamically reconfigure the logical topology of the layer 2 network if needed.
BPDUs
Does not forward, accept network traffic, or learn any MAC addresses. Port receives (but does not send) BPDUs.
blocking
Sends and receives BPDUs, but does not learn MAC addresses, or forward/ process traffic. Calculating a loop-freetopology occurs when listening.
Listening
Learns MAC addresses and populates the MAT to prevent flooding, but does not forward traffic.
Learning
Processes and forwards traffic, while actively learning MAC addresses from incoming traffic; considered normal switch operation.
Forwarding
Administratively shutdown; does not participate in STP or forward frames.
Disabled
is the reference point for all other devices in the STP network. STP selects the root bridge by an election process where the lowest bridge identification wins.
root bridge
based on the802.1w standard, developed to make STP convergence quicker. RSTP responds to network change and re-converge within six seconds. RSTP reduces the number of port states from five to three, which helps speed convergence.
Rapid Spanning Tree Protocol (RSTP)
RSTP port state
No user data is sent over the port. This is comparable to the blocking, listening, and disabled states of the original 802.1d STP specification.
Discarding
forces switch ports to immediately enter the forwarding state, bypassing the STP listening and learning states.
PortFast
Physical Interfaces
Encapsulation methods utilized: HDLC, PPP, Frame Relay and X.25.
Serial/High Speed Serial Interface (HSSI)
Physical interfaces
Encapsulation method utilized: ARPA (Advanced Research Projects Agency) which means that the encapsulation being utilized is Ethernet II on the interfaces.
Ethernet/FastEthernet/GigabitEthernet
Basic Rate Interface (BRI) supports two 64 Kbps B-data channels and one 16 Kbps channel for transmitting control information.
Primary Rate Interface (PRI) supports 23 B channels of 64Kbps each and one 64 Kbps channel transmitting control information for a total bit rate of 1.544 Mbps.
ISDN
is a virtual interface that uses a parent physical interface, allowing for network expansion despite a limited number of physical interfaces. The format for the name is listed below. Notice the decimal point in the name.
Ethernet0/1.1
A logical interface that has the parent physical interface of Ethernet0/1Sub-interfaces allow for management of multiple subnets while only having one physical interface. They are most commonly used in conjunction with VLANs.
Sub-Interface
A virtual interface utilized used to encapsulate data within a separate protocol. Tunnels are used to deliver one protocol across a network using a different protocol or to provide a secure delivery across a network. The following information is needed when configuring a Tunnel interface: Tunnel Interface Number Tunnel Source (Beginning of the tunnel) Tunnel Destination (End of the tunnel)
Default encapsulation method used is Generic Routing Encapsulation(GRE).
Tunnel
A virtual interface configured on the router, used for maintenance/management functions. The loopback interface is commonly configured to provide an IP address when utilizing an ipunnumbered schema or to establish the router id for OSPF and BGP.
Loopback
The null interface provides an alternative method of filtering traffic. Directing undesired network traffic to the null interface avoids the overhead involved with using access lists.
Null
Routed Protocols IPv4, IPv6
Routing Protocols RIP, EIGRP, OSPF
Note: Routing protocols are discussed in detail later in this topic.Static Routing Manually entered routing information
Protocols
Method by which an interface is configured without a dedicated IP address. If interface must provide an IP address (i.e., Traceroute), an IP unnumbered interface uses another local address as its own.
IP unnumbered
Global password for privileged access. Not used if enable secret is set (mainly pre-10.3 systems).
router(config)#enable password
enable password
Overrides the enable password if set.
router(config)#enable secret
If both the enable and enable secret password are set, only the enable secret password provides access.
enable secret
segment configuration to reduce broadcast traffic and improve performance. A VLAN is a logical grouping of users that allows the control of information flow, independent of physical locations. A VLAN allows system administrators to logically separate a device as if it were multiple pieces of hardware.
VirtualLAN(VLAN)
Security by controlling access
Efficient bandwidth by limiting broadcasts
Isolation of failure
Increased flexibility
VLAN advantages
can only belong to and carry traffic for one VLAN. Upon receipt of a frame, a switch examines the destination MAC address, and checks its configuration to see if the destination interface is in the same VLAN as the source interface from which it received the frame. If the interfaces are within the same VLAN, the frame is forwarded. If not, the frame is sent to a router for inter-VLAN communication, or dropped if no router is available.
Access Ports
is a 100-1000 Mbps point-to-point link between switches, or between a switch and a router. Trunk ports carry information for multiple VLANs across their links, or trunk lines.
trunk port
connects two or more switches together and allows like VLANs (e.g., VLAN 10 to VLAN 10) to communicate.
trunking
An older encapsulation method that adds 30 bytes of overhead data to the frame.
InterSwitch Link (ISL)
Adds only four (4)bytes of overhead/data to the frame.
EEE 802.1q (Dot1q)
Support 802.1Q trunks
treat each VLAN as a separate network and utilize separate STP instances for each VLAN configured on the network. PVST and PVST+ allow a VLAN trunk to forward for some VLANs while blocking others.
Per-VLAN STP Plus (PVST+)
Support ISL trunk links
treat each VLAN as a separate network and utilize separate STP instances for each VLAN configured on the network. PVST and PVST+ allow a VLAN trunk to forward for some VLANs while blocking others.
Per-VLAN STP (PVST)
is the addition of VLAN information into a transmitted frame, extending the Ethernet frame to 18 bytes.
Frame Tagging
