Network Fundamentals Flashcards
1
Q
Tell me about global unicast
A
usually /3 3 bits beginning 45 bits global routing prefix 16 bits subnet id 64 bits interface id
2
Q
Tell me about ipv6 multicast
A
FF as first two hexadecimal digits
FF02:1 all nodes in local scope
FF02:2 all routers in scope
8 bits of 1, Flags for 4 bits, Scope for 4 bits, Group ID for 112 bits
ORPT for flags, if R is set to 1 P and T set to 1 (rendezvous point)
3
Q
Tell me about link local address
A
FE80::interface ID
10 Bits Mask + 54 bits 0’s + Interface ID
Can only communicate on network segment
4
Q
Unique Local Address
A
FC00::/7 cannot be routed over public internet (think of it as a private address) eighth bit in first octet is local bit if L is 1 it’s locally assigned
5
Q
Loopback Address
A
::1 aka localhost can be used to verify Ipv6 stack is operating on a device
6
Q
Unspecified Address
A
128 bits are all 0’s :: Used for source address with sending neighbor or router a solicitation (Network advertisement for ip address of the interface) message
7
Q
Solicited Node Multicast
A
corresponding to Ipv6 address in each interface of router begins with FF02::1:FF for first 104 bit, last 24 bits of Ipv6 address, used for duplicate address detection
8
Q
How do we get the EUI address
A
Take Mac address and use it to scale to 64 bit:
Split down middle, insert FFFE in the middle
Convert second hex to binary and flip the 7th bit
9
Q
IPv6 Addresses have
A
Interface ID
Subnet
Global Routing Prefix
10
Q
What does dual stack mean
A
when you run IPv4 and IPv6 on a network
11
Q
Interface ID always occupies the ___ of a Ipv6 address
A
Last 1/2 or 64 bits
12
Q
Class A address has range of
A
1-126 Default mask /8
13
Q
Class B address has range of
A
128-191 Default mask /16
14
Q
Class C address has range of
A
192-223 Default mask /24
15
Q
Class D address is used for ___ and has a range of __
A
multicast, 224-239
16
Q
Class E address is used for ___ and has a range of ___
A
experimental purposes, 240-255
17
Q
Private address ranges
A
A: 10.0.0.0 - 10.255.255.255
B: 172.16.0.0 - 172.31.255.255
B: 169.254.0.0 - 269.254.255.255
C: 192.168.0.0 - 192.168.255.255
18
Q
What’s CDP
A
Cisco Discovery protocol, layer 2 shows information of CDP adjacent devices
19
Q
What destination mac address does CDP send to
A
multicast 01-00-00-0C-CC-CC-CC
20
Q
How do you show neighbors in CDP
A
show cdp neighbors
21
Q
What’s LLDP also known as
A
IEEE 802.1AB
22
Q
What’s the command to know LLDP’s neighbors
A
show lldp neighbors
23
Q
How do you enable LLDP
A
lldp run
24
Q
What are the steps to booting up a router?
A
- POST (Power on self test)
- Execute bootstrap code to locate and load iOS
- Locate Cisco iOS software
- Load Cisco iOS Software
- Locate Configuration in NV ram
- Load into running-config
- Execute Configuration
25
Configuration Register
16 bit value = 4 hex, last value is boot field (4 bits)
26
What are the different configuration options
0x0 = boot into ROM Monitor Mode
0x1 Boot first image in flash
0x2 - 0xF Get image loading instructions from configuration in NVRAM
27
How do you show a router's license?
#show license
28
How do you install a router's license
license install (location of xml file)
29
What does ping send?
Sends ICMP echo request and listens for an ICMP echo reply back ICMP = internet control message protocol or basically troubleshooting message
30
How do you trace a router
#trace ip (dest ip) will send a UDP message with incorrect dest port number packet times out at each router and ip is returned
31
What do you use terminal monitor for
When you cannot see debug message via telnet or ssh
32
What does DHCP stand for
Dynamic Host Config Protocol - can go request iP information from DHCP server
33
What are the steps in a DHCP exchange
DORA Discover broadcast (looking for DHCP server), Offer (DHCP server sends an offer back to client with IP Address), Request (info from specific server), Acknowledgement (sends IP address)
34
What is Administrative distance
the reliability of a routing protocol; helps a router select the best path when multiple are available - the lower the better
35
What is the administrative distance of a direct connection
0
36
What is the administrative distance of a static connection
1
37
What is the administrative distance of a eBGP protocol
20
38
What is the administrative distance of a EIGRP protocol
90
39
What is the administrative distance of a OSPF protocol
110
40
What is the administrative distance of a RIP protocol
120
41
What are the three packet forwarding options and how do they work?
Process switching, cpu looks through each and every decision
Fast switching has a route cache which memorizes what comes through so not everything has to pass CPU
Cisco Express Forwarding has a FIB with a routing table and adjacency table which allow data to go directly without touching CPU
42
How do you check an ip routing table? (command)
#show ip route
43
What is the format for interface addressing
Module/slot/port
Module: what controls it (starts at 0 which is motherboard)
Port: numbering starts at 0, moves from right to left and bottom to top
44
How do you check Cisco iOS (command)
show version
45
How do you view Cisco router configuration (command)
#show running-config
46
How do you view interface status (command)
show ip interface brief
47
how do you get to a certain interface (command)
show interface (interface id 0/0)
48
How do you reconfigure a router's hostname (command)
config# hostname (hostname)
49
How do you assign an IPv4 to interface
```
# inferface fa0/0
(config-if) ip address (ip address) (mask)
```
50
How do you assign an iPv6 to interface
```
(config-if) ipv6 enable
ipv6 address (address)/mask
```
51
How do you assign an iPv6 to interface
```
(config-if) ipv6 enable
ipv6 address (address)/mask
```
52
What's the structure of an ethernet frame
7 bytes preamble 1 byte SFD which tells next bit is mac address 6 byte destination mac address 6 bytes source mac address 2 byte type Frame check sequence 4 bytes
53
What is a shared segment?
It's a segment where only one frame can travel on the shared segment at any time
54
What is the split horizon rule
A rule used by routing protocols where a router advertising a route out of the interface on which the route was learned is prevented to prevent overriding
55
What's the two numbers on a routing table ie 90/120
Administrative Distance/Metric (how far a remote network is from a router dependent on routing protocol used)
56
How do you pull up a routing table for OSPF
show ip ospf rib
57
How do you pull up Cisco express forwarding routing table
show ip cef
58
How does a router on fast ethernet know about the destination Mac address
It sends out an Address Resolution Protocol or ARP broadcast
59
How do you show ARP mac addresses
show ip arp
60
how do you calculate the wild mask address
Subtract a network's subnet mask from 255.255.255.255
61
What's the purpose of a passive interface
prevents Hello messages from being sent out of a certain interface while still allowing network to be advertised
62
What does passive interface default do?
Suppresses any hello messages from being sent out of any router interface participating in routing protocol
63
What does the network command do?
Tells the router which interfaces should participate in the routing process do network ip address wildcard address
64
What prevents RIP from being expanded to larger networks
RIP has a max hop count of 15, that is any network with hop count 16 is deemed unreachable
65
What prevents RIP from being expanded to larger networks
RIP has a max hop count of 15, that is any network with hop count 16 is deemed unreachable
66
What is convergence
RIP - amount of time a dynamic routing protocol takes to reroute around a network failure
67
What is summarization
routing protocol feature that allows multiple routes to be represented by a summary route (takes common bits and makes them a mask)
68
What's the difference between a interior gateway protocol and exterior gateway protocol
Interior gateway protocol is a routing protocol running within an autonomous system
Exterior gateway protocol is a routing protocol running between autonomous systems
69
What are some examples of interior and exterior gateway protocol
Interior: RIP, OSPF, EIGRP
Exterior: BGP (Border Gateway Protocol)
70
What are the three classifications of routing protocols
Distance-Vector: Given a path and metric for each network to connected peers, EIGRP and RIP
Link-State: Each router advertises state of links to every other router creating a topography, then uses Dijkstra, OSPF and ISIS
Path Vector - knows the exact path taken by adding each network in path and forwarding advertisements, BGP
71
What protocol does RIP use
Distance Vector
72
What protocol is OSPF
Link State
73
What protocol is EIGRP
Advanced Distance Vector (if network changes then update)
74
What protocol is BGP
Path Vector
75
What's the difference between RIPv1 RIPv2 and RIPng
RIPv1: Broadcasts to advertise to neighbors, No VLSM
RIPv2: Multicast to 224.0.0.0/9, VLSM, IPv4
RIPng: Multicast to FF02::9 VLSM support and IPv6
76
What's a poison reverse
lost a connected network, so router will send a router advertisement of connection with 16 hop count to prevent traffic being sent down
77
How do you view protocol?
show ip protocols
78
What's a collision
Two stations transmitting a shared segment at the same time
79
What's jamming
continued transmission of a frame that has collided to allow all devices on a segment to detect the collision
80
What's an ethernet hub
all ports on an ethernet hub belong to the same collision domain
81
What's the ethernet switch
Each port is in its own collision domain
82
What's the difference between duplex and half-duplex
Duplex can send and receive at the same time, Half Duplex cannot send/receive at the same time
83
What's a broadcast domain
Defines how a broadcast travels in a network, which contains the destination mac address
84
All ethernet hub ports
belong to the same broadcast domain and collision domain
85
All ports on ethernet switch will
belong to the same broadcast domain but separate collision domains
86
All ports on a router belong to
a separate broadcast domain and different collision domain
87
If a switch does not know a Mac address, what does it do?
It floods the ports, that is it sends frames out of all ports except the received port;
88
What's an ARP broadcast
Flooded through FFFF.FFFF.FFFF
89
What's the naming format for an interface in a switch
switch in stack/slot in module (0)/port number
90
How do you show a mac address table
show mac address-table
91
How do you see a current configuration on a switch
show run
92
How do you set an enable password on a Cisco switch
in config mode type enable password cisco or enable secret (password)
93
How do you set exec timeout on a Cisco switch
In line config mode type: exec-timeout (min) (sec)
94
Explain the working behind a mac flooding attack
A hacker can connect to a switch and overflow the CAM or Mac address table; at the same time the switch since it doesn't know the dest. mac address so it floods frames out of all ports
95
What's the pre-requisite for port security
the port has to be an access port (cannot be trunked)
96
How do you turn on security?
get into the interface
switchport mode access
switchport port-security
97
How do you specify the max # of mac addresses?
switchport port-security maximum (number)
98
How do you specify a mac address
switchport port-secuirty mac-address (number)
99
To set up sticky or dynamic learning
switchport port-security mac-address sticky
100
What are the port security violation options
protect - mac addresses not allowed are dropped
restrict - drop disallowed and increment security violation counter
shutdown - switch will shut down
101
How do you remove a port out of err disable
go to port and put no shutdown
102
To see port security type, type
show port-security
103
How do you change recovery time on error disable port automatic recovery
errdisable recover cause psecure-violation
104
To change error disable port automatic recovery type
errdisable recover interval (time in sec)
105
Shut down all unused ports and put them in an unused VLAN
```
conf term
vlan 999
name NULL_VLAN
int range fa 1/0/1 - 24
shutdown
end
```
to turn on, go to port and say no shutdown
swithcport access vlan 9999
show vlan
106
How do you show an access list?
show access-lists
107
What does trunking add to a frame?
It tags them, adding 4 bytes - 12 bits to the id of the VLAN and 3 bits to the priority/quality of service
108
Explain the 4 trunking modes and what they entail
access - forces a port to become an access port
trunk - forces a port to become a trunk port and will send DTP frames
dynamic desirable - initiates negotiation of a trunk
dynamic auto - passively waits for the remote switch to initiate negotiation of a trunk (if it only receives one)
109
What does DTP stand for
Dynamic Trunking Protocol
110
How do you view trunking
show interfaces fa 1/0/12 switchport
111
How do you show trunks on a switch?
show interfaces trunk
112
How do you pick which VLANs are allowed to flow over a trunk?
switchport trunk allowed vlan ?`
113
How do you check interface status for a particular interface
show interfaces (for all) or show interfaces fa 1/0/2
114
What is a CRC
Frame check sequence, # of times the volume does not match between transmission and recession, if CRC's match on both ends frame has not been modified
115
What is a runt
frame runs too small and bad CRC
116
What is a giant
frame runs too big and bad CRC
117
What two modes don't match up
full duplex and half duplex will not work
118
How do you check a port's VLAN membership
show vlan brief
119
How do you add a port to a VLAN
switchport access vlan (number)
120
How do you set the default gateway
ip default-gateway
121
What are the three trunking configurations of Voice VLAN
Single VLAN Access Port: one VLAN shared with phone and computer VLAN, useful if phone is on computer or 3rd party
Multi VLAN Access Port: one VLAN but can support a second one if the second one is a voice VLAN
Cisco phone learns which VLAN it is in via CDP messages
Higher priority on voice
Trunk Port
Compatible with CDP and LLDP protocol
122
What is NTP
Network Time Protocol, help interpret event logs, UDP port 123, stratum number of a time source indicates how accurate the time is
123
Which of the following commands will disable SSH and Telnet connections on a switch?
transport input none
124
How do you set NTP as master
in conf term ntp master (stratum number)
125
How do you point a router to NTP server
from router config# ntp server (ip address)
clocktimezone (name) (hours)
To verify:
show ntp status
126
What is NAT used for
Translating addresses from within a network to the global internet area of the network
127
What's the difference between global and local addresses
global addresses are publicly routable whereas local addresses are not routable
128
What's the difference between inside and outside addresses
Inside addresses mean that they are inside the network (private) while outside addresses are public addresses
129
How do you config a router as a DHCP server
ip dhcp pool pc
130
How do you see DHCP addresses
show ip dhcp binding
131
How do you point a router to a DHCP server
ip helper-address (dhcp server ip)
132
What's the difference between coaxial and twisted pair cabling
Coaxial has conductor wrapped outside with insulator wrapped around in conductor wrapped in outside wire, twisted pair has individual pairs, sometimes shielded (wrapped around each pair) or unshielded
133
What is RG 59 used for
carry video over short distances
134
What is RG 58 used for
Carrying 10 Base 2 Ethernet
135
What is category 3 used for
10 Base X connections
136
What does the number before base refer to (ie 10 base 2, 100 base 2)
bits per second on ethernet speed
137
What is a DB9 connection used for
Asynchronous connection and connection to modem
138
What is a RJ 45 cable used for
Ethernet cables, Cat 5 and 6 Cables, used for ethernet connections
139
What is RJ 11 used for
Telephone connections
140
What is BNC used for
Used for data connections, 10 Base 2 Connections
141
Which pins are crossed over for a ethernet cable
1,2 and 3,6
142
How do you display a banner on a switch?
banner ?
143
How do you remove a license
disable then reload 1. license boot module disable 2. license clear (license)
144
How do you set MTU in a ping
ping enter set DF bit in IP header: yes sweep: yes
145
How do you recover the password of a router
```
break into rommon then switch configuration register to 0x2142, reset router to log in without password
copy startup config running config
// config register back
config# config-register 0x2102
copy-running config startup config
```
146
How do you configure an evaluation license
license boot machine chasis technology-package (license)
147
What does ping send?
ping enter set DF bit in IP header: yes sweep: yes
