ICND1 Flashcards
OSI Layers
Physical, Data Link, Network, Transport, Session, Presentation, Application
What is the data link layer address for Ethernet
MAC
What are the non-overlapping channels in the 2.4 Ghz frequency for wireless access points.
1, 6, and 11
Basic function of IPS
Learn normal behavior of network and block or warn when an abnormality is observed.
IOS Configuration, interface mode, ‘ntp broadcast’
Sends NTP broadcasts
What do the following port light colors indicate on a Cisco switch?
no light green blinking green alternating green-amber amber blinking amber
no light - no link, or port is admin down.
green - link present
blinking green - activity (normal operation)
alternating - link fault: errors such as excessive collisions, CRC, alignment, and jabber.
amber - port blocked by STP while listening or learning
blinking amber - port is in STP blocking state
What conditions might cause a switch port status light to remain unlit?
admin down or link down.
Link down may be due to encapsulation or other layer 2 protocol mismatch, a bad or incorrect cable, or a lack of signal.
For numbered ACLs what are the number ranges for standard and extended IP ACLs
standard: 1-99 and 1300-1999
extended: 100-199 and 2000-2699
Describe the OSI Application Layer
This layer interacts directly with applications.
These services include FTP, SMTP, HTTP, DHCP, et al.
Describe the OSI Presentation Layer
This is not always used. It handles translation, compression, and encryption. Translation changes the data to be understood by different types of computers such as changing LF to CRLF in an ASCII FTP transfer.
Describe the OSI Session Layer
Creates, manages, and terminates sessions between communicating nodes. These are APIs such as NetBIOS, TCP/IP Sockets aka Python SocketIO, and RPC.
Describe the OSI Transport layer
It has two main parts. One is keeping track of what data comes from what application and combining that data into a single flow for use by the lower layers. The receiving device reverses this operation. Dividing the data into segments ready for layer 2 and 3 encapsulation is also done here.
Part 2 TCP/UDP - providing either connection-oriented (TCP) or connectionless (UDP) services. Connection-oriented services include flow control, keeping packets in order, recovering from lost transmissions or errors. Connectionless services do almost nothing apart from keeping track of which application the traffic belongs to. They are called best-effort because if the data is lost there is no attempt to recover it.
Describe the OSI Network Layer
This layer handles logical addressing, routing, datagram encapsulation, fragmentation and reassembly, and error handling and diagnostics. Error handling and diagnostics doesn’t include data recovery. The most common example of this is a routing protocol using a ‘hello’ protocol to verify the link is up.
Describe the OSI Data Link Layer
This includes logical link control, media access control, data framing, local addressing, and error detection and handling. Common error detection includes the checksum on Ethernet frames.
Describe the OSI Physical Layer
This includes hardware specifications, encoding and signaling, and data transmission and reception.
Layer 1 devices are CSU/DSU, transceivers, and repeaters that take bit streams and convert or repeat them without regard to the structure at the other layers.
What are the 7 layers of the OSI model
Physical, Data Link, Network, Transport, Session, Presentation, and Application
What are the major letters used in the ‘show ip route’ command and their associated protocol
C - connected S - static R - RIP B -BGP D - EIGRP EX - EIGRP external I - IGRP (deprecated) O - OSPF i - IS-IS o - ODR
Which protocol is used by Ethernet to control transmission over a shared medium. Which similar protocol is used by WiFi?
CSMA/CD for Ethernet
(Carrier Sense Multiple Access / Collision Detection)
CSMA/CA for WiFi (Carrier Sense Multiple Access / Collision Avoidance)
Answer one to \_\_\_\_ for the following: Unicast Multicast Broadcast Anycast
Unicast: One to One
Multicast: One to Many
Broadcast: One to All
Anycast: One to Any
Which method do network devices use to translate a name to an IP address
DNS
What is the RFC number for private IPv4 address space?
RFC 1918
List the RFC 1918 address ranges
- 0.0.0 - 10.255.255.255
- 16.0.0 - 172.31.255.255
- 168.0.0 - 192.168.255.255
List differences between UDP and TCP
TCP deliveries all packets in order
UDP delivers whatever packets arrive.
TCP has higher overhead.
UDP is better for real-time applications like VoIP
TCP is connection-oriented
UDP is connectionless
TCP is slower
TCP does error checknig and error recovery
UDP does error checking but discards and does not recover
TCP has a handshake UDP does not
What is TCP sliding window?
The adjustment in quantity of data sent before the sender receives an acknowledgement
What are the 3 steps in a TCP 3-way handshake.
SYN (initiator)
SYN-ACK (responder)
ACK (initiator)
List the differences between the TCP/IP reference model and the OSI reference model. (Layer names will be covered on other slides)
OSI is protocol independent
OSI is a reference model and TCP/IP is an implementation
OSI model has 7 layers and the TCP/IP model has 4 layers.
What OSI layer(s) provider similar functionality to the TCP/IP Application layer?
Application, Presentation, and Session
What TCP/IP model layer provides the functionality of the OSI Presentation layer?
Application
What TCP/IP model layer provides the functionality of the OSI Session layer?
Application
What TCP/IP model layer provides the functionality of the OSI Transport layer?
Transport
What TCP/IP model layer provides the functionality described by the OSI Network layer.
Internet layer
What TCP/IP model layer provides the functionality described by the OSI data-link layer?
Network Access layer
What TCP/IP model layer provides the functionality described by the OSI physical layer?
Network Access layer
What OSI layer(s) describe the functionality of the TCP/IP Transport layer?
Transport layer
What OSI layer(s) describe the functionality of the TCP/IP Internet layer.
Network layer
What OSI layer(s) describe the functionality of the TCP/IP Network Access layer
Data Link layer and Physical layer
List the main IOS Command modes
User EXEC Privileged EXEC Global configuration Interface configuration Subinterface configuration ROM monitor
List configuration required for SSH access
line vty 0 4 login local transport input ssh/all username xxx secret xxx hostname router ip domain-name example.com crypto key generate rsa
Command to view table of interface mac address mapping
show mac address-table
Command to view directly connected Cisco devices
show cdp neighbors
Commands to enable lldp globally, disable it on an interface, and view discovered neighbors.
global: lldp run
interface: no lldp transmit
EXEC: show lldp neighbors
What is LLDP an acronym for?
Link Layer Discovery Protocol
Describe the three possible response types for switchport port-security
protect: block traffic from any MAC addresses beyond the number allowed
restrict: same as protect but will log violations
shutdown: will err-disable the port if the number of allowed MAC addresses are exceeded
Command for a sticky mac in port security
switchport port-security mac-address sticky
Command to limit number of mac addresses on port
switchport port-security maximum n
Command to enable port security
switchport port-security
Command to configure port security response type
switchport port-security violation [protect, restrict, shutdown]
Command to set port as static access
switchport mode access
Command to set port to attempt to negotiate trunk with DTP capable switch
switchport mode dynamic desirable
Default switchport DTP mode
dynamic auto
List some conditions which will cause a switch to have its VLAN database replaced by a neighboring switch
If VTP domain is null and packet is received from switch with non-null domain. If the password is set on the non-null switch then the null switch won’t inherit the VTP setup.
A switch running in VTP client mode version 2 on cbtnuggets.com domain is not receiving the revision updates from the VTP server on version 2 from domain CBTNuggets.com. What is the problem?
Domain names don’t match - case sensitive.
Command for routing protocol details
show ip protocols
Command too apply ACL to vty
access-class n [in|out]
Configure DHCP server range 192.168.1.20-100.
ip dhcp excluded-address 192.168.1.1 192.168.1.19
ip dhcp excluded-address 192.168.1.101 192.168.1.254
ip dhcp pool POOL
network 192.168.1.0 /24
default-router 192.168.1.1
dns-server 8.8.8.8 4.2.2.2
Configure NAT overload to the Fa0/1 interface IP for all RFC 1918 addresses behind Fa0/0.
access-list 1 permit 10.0.0.0 0.255.255.255
access-list 1 permit 172.16.0.0 0.15.255.255
access-list 1 permit 192.168.0.0 0.0.255.255
interface Fa0/0
ip nat inside
interface Fa0/1
ip nat outside
ip nat inside source list 1 interface Fa0/1 overload
Configure a NAT pool with the four IP address 200.1.1.2 through 200.1.1.5.
ip nat pool NAME 200.1.1.2 200.1.1.5 prefix-length 24
Configure a static NAT so that
the host 10.50.1.20 connected to Fa0/0 will appear with a source of 200.2.1.1 to the ISP on Fa0/1.
interface Fa0/0
ip nat inside
interface Fa0/1
ip nat outside
ip nat inside source static 10.50.1.20 200.2.1.1
What is the IPv6 broadcast address?
Trick question there is no IPv6 broadcast.
Describe EUI-64
first 24-bits of MAC, followed by FFFE, followed by second 24-bits of MAC.
List major IPv6 address type prefixes
Global Unicast - 2000::/3
Unique Local - FD00::/8 (FC00::/7 with FC00::/8 undefined)
Link Local - FE80::/10
Multicast -FF00::/8
What is used in the host portion of a link local address on a Cisco router.
Modified EUI-64 address
Command to turn off all IPv6 router advertisements both solicited and unsolicited
IPv6 nd ra suppress all
note: ‘all’ keyword introduced in 15.1(3)T3
What command enables Stateless Address Auto Configuration on interfaces with IPv6 addresses?
ipv6 unicast-routing
Configure ipv6 route to network 2001:56::/64 with next-hop 2001:210::1
IPv6 route 2001:56::/4 2001:210::1
Syslog severities are logged from 0 to _____. ____ is the most severe level while ___ is the least.
7
0, 7
Command to enable seeing console messages on telnet/ssh vty
terminal monitor
Command to send syslog messages to another host
logging host x.x.x.x
Command to set daylight savings time
clock summer-time XX recurring
Commands to configure NTP
1) Listen for broadcasts
2) Listen for multicasts
3) Poll server directly
1) interface: ntp broadcast client
2) interface: ntp multicast client
3) global: ntp server x.x.x.x
List the four major configuration registers
0x2100 ROMMON
0x2101 RXBOOT
0x2102 Boot Normally
0x2142 Ignore NVRAM
List where IOS looks for a bootable images in order
Images specified by “boot system” commands
First IOS image in flash
Broadcast for a TFTP server
When in ROMMON how to set to boot with no config
confreg 0x2142
Configure port security to re-learn MAC addresses every 10 minutes
switchport port-security aging time 10
Configure a ROAS subinterface for Fa0/0 VLAN 2
interface Fa0/0.2
encapsulation dot1q 2
ip address x.x.x.x
Configure logging to send only warnings level 4 and below to syslog hosts
logging trap warnings
Command to set time zone
clock timezone XXX -n
List steps to obtain and install a license on an IOS 15 device
1 - Purchase license and receive PAK key
2 - Get license file from CLM or www.cisco.com/go/license using UDI
3 - Use the CLI to install the .lic file
How do you find the UDI and what is it a combination of
show license udi
It is a combination of the product id (PID) and SN. (ex: CISCO2911/K9FTX1524PIRE
Command to show licenses
show license all
show license detail
Command to show features enabled on device
show license feature
Install license
license install flash0:licensefile.lic
Backup license
license save flash:filename
Unistall a license
license boot module x x x disable do reload license clear x conf t no license boot module x x x disable do reload
What command sets the local router as an authoritative time source
ntp master
What commands show cdp neighbor information
show cdp show cdp entry * show cdp neighbors show cdp neighbors detail show cdp interface show cdp traffic
How to configure the router to generate a link-local IPv6 address
Either statically assign an IPv6 address or autoconfig. Link-local will be generated at the same time.
What is another name for ROMMON mode?
Router diagnostic mode (maybe?)
List and describe DHCP message types
DHCPDiscover - First packet sent by host
DHCPOffer - Response from server includes IP, mask, gateway, and other information.
DHCPRequest - This is the response to the DHCPOffer or simply a request if renewing
DHCPDecline - The client determines the offered configuration parameters are invalid and sends a decline message.
DHCPAck - This comes from the server to acknowledge the request
DHCPNak - This comes from the server if DHCPRequest has an unavailable IP
DHCPRelease - The client sends this when it no longer needs the lease.
DHCPInform - This is used to obtain other network information if the client already has an IP manually configured or obtained elsewhere.
When running a classful routing protocol what command allows it to use the default route even if it already knows some routes in a major network?
ip classless
How many NTP stratum levels can be used?
16
What should be included in a login banner?
- Notice that use is permitted only by authorized personnel
- Notice that unauthorized use is unlawful and may be prosecuted
- Notice that access and use may be monitored and logged for use in court
- It should not include words like ‘welcome’
List and describe colors of the system LED on Cisco switches
off - no power
solid green - operating normally
solid amber - not operating normally
List Cisco password best practices
- 10 characters
- Must begin with alphabetic character
- Include U/L/N/S
- No dictionary words even as part of password
What command disables cdp on a router?
no cdp run
List device type codes for CDP
R - Router T - Transparent Bridge S - Switch H - Host r - Repeater P - Phone D - Remote M - Two-port Mac Relay
List device type codes for LLDP
(R) Router (B) Bridge (T) Telephone (C) DOCSIS Cable Device (W) WLAN Access Point (P) Repeater (S) Station (O) Other
What is the mac address-table default timeout. Bonus, how do you change it?
5 minutes
mac address-table aging time ss
Configure arp timeout
interface: arp timeout ss
View arp timeout
show interfaces
What is the arp timeout default?
4 hours
View CAM table timeout
show mac address-table aging
What DHCP configuration command is used to provide phones or other hosts that need a tftp server that address?
next-server x.x.x.x
What is equivalent to ntpq -p
show ntp associations
How to tell if the clock is synchronized
No asterik and/or ‘show ntp status’
How to find ntp protocol or bad version packets?
show ntp packets
Command to verify md5 hash of file
verify /md5 filesystem:filename [hash]
List SYSLOG level names with their associated numbers
Emergency - 0 Alert - 1 Critical - 2 Error - 3 Warning - 4 Notification - 5 Informational - 6 Debugging - 7
Command to suppress CDPv2 advertisements
no cdp advertise-v2
What OSI layer includes SCP and service requests
Session Layer
