Summary of course materials ICND1 100-101

According to the results of the survey publish a summary of the course ICND1 100-101.

What topics are there: TCP / IP network model, OSI model, Ethernet (cable types), HDLC. By IPv4 addressing: class networks, private addresses, methods of transmitting traffic on the network. VLANs, CDP, comparison of routing protocols, NAT, IPv6, ACLs. Very briefly, mostly data here, and not an explanation of the principles of work.
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There is not much: explanations of the operation and configuration of routing protocols, switching in networks, explanations, for example, how to determine if the IP address of a particular subnet belongs (such questions often occur), no classless networks, VLSM, IOS, troubleshooting.

TCP / IP network model

TCP / IP original	TCP / IP updated	Protocol examples	Package name
Application	Application	HTTP, POP3, SMTP
Transport	Transport	TCP, UDP	Segment (UDP - Datagram)
Internet	Network	IP	Packet
Link	Data link	Ethernet, Point-to-Point Protocol (PPP), T1	Frame
	Physical

OSI model

Level name	Protocols	Devices
Application (L7)	Telnet, HTTP, FTP, SMTP, POP3, VoIP, SNMP	Hosts firewalls
Presentation (L6)
Session (L5)
Transport (L4)	TCP, UDP	Hosts firewalls
Network (L3)	IP	Router
Data Link (L2)	Ethernet (IEEE 802.3), HDLC	LAN switch, wireless access point, cable modem, DSL modem
Physical (L1)	RJ-45 Ethernet (IEEE 802.3)	LAN hub, LAN repeater, cables

Mnemonic to remember the order of levels: Please Do Not Take Sausage Pizzas Away
(Please do not take pizza with sausages with you).

Ethernet technology, medium and maximum segment length

Ethernet	Cable type	Maximum length, m
10 BASE-T	UTP CAT3 or better, 2 pairs	100
100 BASE-TX	UTP CAT5 or better, 2 pairs	100
100 BASE-FX	Multimode fiber	400
1000 BASE-CX	STP	25
1000 BASE-T	UTP CAT5e or better, 2 4 pairs	100
1000 BASE-SX	Multimode fiber	275, 550
1000 BASE-LX	Multimode fiber	550
1000 BASE-LX	Singlemode fiber	10,000 (in the book for exam 100-101, 5 km is indicated - a lot of them)

Using pins in 10BASE-T and 100BASE-TX standards

Transmits on Pins 1,2	Transmits on Pins 3.6
PC NICs	Hubs
Routers	Switches
Wireless Access Point (Ethernet interface)	-

Full-duplex, Half-duplex

If there is no autonegotiation, according to the IEEE standard, duplex transmission parameters are selected as follows:

• If the rate is 10 or 100 Mbps, then half-duplex transmission is used.
• If the speed is 1000 Mbps, then duplex is used.

Interfaces operating at speeds above 1 Gbps always use full-duplex transmission.
When using duplex transmission there are no collisions.

WANs

HDLC
One of the data link layer protocols in point-to-point data transfer channels (High-Level Data Link Control) is a high-level data link control protocol.

By changing the standard protocol specification, Cisco created a proprietary version of it, adding a Protocol Type field to identify the type of packet contained within the frame:
Bytes

one	one	one	2	Var	2
Flag	Address	Control	Type	Data	FCS

Internet Access WAN Links: Leased Line, DSL, Cable.

IPv4 addressing

Class networks

Class	First Octet Range	Valid network numbers	Hosts per network	Number of Networks
reserved	0
A	1 - 126	1.0.0.0 - 126.0.0.0	16 777 214	126
reserved	127
B	128 - 191	128.0.0.0 - 191.255.0.0	65,534	16 384
C	192 - 223	192.0.0.0 - 223.255.255.0	254	2,097,152
D (multicast)	224 - 239
E (experimental)	240 - 255

Private IP Addresses

Address Class	Reserved Address Space
A	10.0.0.0 through 10.255.255.255
B	172.16.0.0 through 172.31.255.255
C	192.168.0.0 through 192.168.255.255

Methods of transferring traffic in networks:

Unicast traffic (single-purpose packet transmission) is used primarily for services of a “personal” nature. Each subscriber can request personal video content at an arbitrary, convenient time.

Broadcast traffic (packet broadcasting) uses a special IP address to send the same data stream to all subscribers of this IP network. For example, such an IP address may end in 255, for example 192.0.2.255, or have 255 in all four fields (255.255.255.255).

Multicast traffic (multicast packets) is used to stream video when it is necessary to deliver video content to an unlimited number of subscribers without overloading the network. This is the most commonly used type of data transmission in IPTV networks, when a large number of subscribers watch the same program. Multicast traffic uses a special class of destination IP addresses, for example, addresses in the range of 224.0.0.0 - 239.255.255.255. These may be class D IP addresses.

Applications, their port numbers and protocols

Port number	Protocol	application
20	Tcp	FTP data
21	Tcp	FTP control
22	Tcp	Ssh
23	Tcp	Telnet
25	Tcp	SMTP
53	UDP, TCP	DNS
67, 68	UDP	DHCP
69	UDP	Tftp
80	Tcp	HTTP (WWW)
110	Tcp	Pop3
161	UDP	SNMP
443	Tcp	SSL

Collision and Broadcast Domains



Cisco 2960 Catalyst. LED Switch Indicators

room	Title	Description
one	SYST (system)	General system status (green - power is on and the switch is functioning normally, IOS is loaded, orange - POST (Power on Self Test) has ended with errors and IOS has not been loaded, it is off - power is off)
2	RPS (redundant power supply)	Additional power supply status
3	STAT (status)	The status for each port (blinks green - the connection is working, data is transmitted through the interface, is lit green - the connection is working, but data is not being transmitted, it is blinking orange - the interface is administratively turned off or has been dynamically disconnected for some reason, turned off - the connection is not working)
four	DUPLX (duplex)	Lights green - the port is operating in full duplex mode, turned off - in half duplex
five	SPEED	Flashing green - 1 Gbit / s, Lit green - 100 Mbit / s, Off - 10 Mbit / s
6	Mode	Modes button
7	Port	Indicators indicate different states depending on which mode is selected by the Mode button.

Types of switch memory

RAM (Working Memory and Running Configuration)

Flash (Cisco IOS Software)

ROM (Bootstrap Program)

NVRAM (Startup Configuration)

Virtual LANs

In the local network, all devices are in the same broadcast domain.

Trunking protocols

- ISL (Inter-Switch Link). The protocol was created by Cisco many years before the IEEE organization developed its own. The protocol provides for the encapsulation of each Ethernet source frame in the header and the ISL trailer. Currently, some modern devices no longer support this protocol. (Cisco Catalyst 2960).

- 802.1Q. Developed by IEEE. Both protocols tag each frame VLAN ID. But the 802.1Q protocol does not encapsulate the original frame. Instead, it is provided to insert a 4-byte extra VLAN header in the Ethernet header of the source frame.

DA

SA

Tag

Type

Data

FCS

Tag:

Type

Priority

Flag

VLAN ID (12 bits)

VLAN IDs:

1-1005 - normal range
1006 - 4094 - extended range

802.1Q does not add a header to frames in its own (native) VLAN.
Both protocols support the use of multiple STP instances.

Trunking Administrative Mode Options (administrative mode of trunk connection, defined using the switchport mode command)

Options	Description
access	Prevents use of the trunk connection. The port always acts as a non-backbone (in network access mode)
trunk	Always use trunk connection
dynamic desirable	Initiates the transmission of channel mode negotiation messages and responses to negotiation messages in order to dynamically determine whether to start using a trunk connection, and also defines encapsulation in the trunk connection
dynamic auto	Passively waits for a message to negotiate the trunk connection, after which the switch responds and negotiates whether to use the trunk connection, and if so, matches the type of trunk connection

Coordination of administrative regimes on 2 switches

	Access	Dynamic auto	Trunk	Dynamic Desirable
Access	Access	Access	Do not use	Access
Dynamic auto	Access	Access	Trunk	Trunk
Trunk	Do not use	Trunk	Trunk	Trunk
Dynamic Desirable	Access	Trunk	Trunk	Trunk

CDP (Cisco Discovery Protocol)

The Cisco Device Discovery Protocol can be a useful tool to verify the information provided in the network diagram, as well as fill in the missing information about devices and network topology.

Show cdp group commands

Team	Description
show cdp neighbors [type number]	Displays one summary line with information about each adjacent device or only about that neighboring device that is connected to a specific interface, if that interface is specified
show cdp neighbors detail	Displays a large amount of information about each adjacent device (approximately 15 lines), representing each adjacent device separately.
show cdp entry name	Displays the same information as show cdp neighbors detail, but only for one specified neighboring device (case-sensitive)

Network Switch Interface Status Codes

Line condition	Protocol Status	Interface state	Cause
Administratively Down	Down	disabled	Apply the shutdown command on the interface
Down	Down	notconnect	The cable is not connected, faulty, the pin layout is wrong, the device speeds do not match, the device at the other end of the cable is turned off or its interface is stopped (power-off, shutdown, err-disabled)
Up	Down	notconnect	Practically not found
Down	Down (err-disabled)	err-disabled	Interface blocked by port security (Port security has disabled the interface)
Up	Up	connected	Works

Actions taken by the port security tool, depending on the established violation correction mode

Remedy mode	Destroying non-compliant traffic	Destroying all traffic after a violation occurs	The interface is set to "err-disabled" as a result of a violation	Increasing counter values ​​due to detection of each new violation
shutdown	Yes	Yes	Yes	Yes
restrict	Yes	Not	Not	Yes
protect	Yes	Not	Not	Not

Routing protocols are divided into 2 large categories:

Internal (IGP) - Internal Gateway Protocols - used within a single autonomous system (AS - autonomous system, a network under a single administrative control, owned by one organization)

Exterior Gateway Protocols (EGP) - used between autonomous systems

Algorithms IGP routing protocols

• distance vector (Bellman-Ford) (DV)
• considering the state of the channel (link-state, LS)
• balanced hybrid (extended vector distance)

IGP protocol comparison

Property	RIP-1	RIP-2	EIGRP	Ospf	IS-IS
Classless, supports VLSM masks, forwards the mask in route announcements	Not	Yes	Yes	Yes	Yes
Algorithm	DV	DV	advanced DV	LS	LS
Supports manual summation	Not	Yes	Yes	Yes	Yes
Corporate	Not	Not	Yes (but RFC was released in 2013)	Not	Not
Routing table updates are sent to the multicast address	Not	Yes	Yes	Yes	-
Convergence	Slow	Slow	Quickly	Quickly	Quickly

IP IGP Metrics

Igp	Metrics	Description
RIP-2	Hop count	Number of routers (transit devices) between this router and the recipient network
Ospf	Cost	The sum of the cost of all channels along the route of the packet, usually based on the value of the bandwidth
EIGRP	Composite bandwidth and delay	Calculated from the bandwidth values ​​of the slowest channel on the route and the cumulative delay for such a route.

Protocol Comparison

Characteristic	RIP-2	Ospf	EIGRP
Metrics	Hop count	Cost	Composite bandwidth and delay
Does periodic route announcements	Yes (every 30 sec.)	Not	Not
Full or partial announcements are sent.	Complete	Partial	Partial
Destination announcements routing	224.0.0.9	224.0.0.5 and 224.0.0.6	224.0.0.10
Maximum metric value ("infinite metric")	sixteen	2 ^ 24 - 1	2 ^ 32 - 1
Is load balancing supported on unequal channels (i.e., channels with different metrics)	Not	Not	Yes

Standard Administrative Distance Distances in IOS (Default Administrative Distances)

Route type	Administrative Distance
Connected	0
Static	one
BGP (external routes)	20
EIGRP (internal routes)	90
IGRP	100
Ospf	110
IS-IS	115
Rip	120
EIGRP (external routes)	170
BGP (internal routes)	200
Unusable	255

ACL (Access Control Lists)
Access Control Lists

Types of lists

Standard Numbered ACLs (1-99) - standard numbered
Extended Numbered ACLs (100-199) - Extended Numbered
Additional ACL Numbers (1300-1999 standard, 2000-2699 extended) - additional
Named ACLs - Named

Improved Editing with Sequence Numbers - advanced editing with sequence numbers.

Standard Access Control Lists

access-list access-list-number {deny | permit} source [source-wildcard] 

Standard lists should be located near the recipient of the packages, so as not to accidentally discard the necessary packages.
Standard lists allow you to check only the address of the sender in the package.
The list is searched sequentially, the packet is processed according to the first matching rule (first-match logic).
The standard action, if the package is not associated with any of the commands in the list, is a ban.

Application of the access control list on the selected interface of the router taking into account the desired directionality using the interface configuration mode command:

 ip access-group number {in | out} 

Extended Access Control Lists

Fields checked using extended lists only: destination IP address, parts of the destination IP address specified using an inverted mask, protocol type, source port, destination port, TCP streams, IP TOS byte, IP packet priority.

The access-list command should use the tcp keyword to check TCP port numbers, udp to check UDP port numbers. The ip keyword does not provide verification of the port number.

Parameters with indication of the port of the sender and receiver are positional. Their location in the command determines whether the parameter is used to check the port of the sender or the receiver:

packet filtering based on destination port number

 access-list 101 permit tcp 172.16.1.0 0.0.0.255 172.16.3.0 0.0.0.255 eq 21 

packet filtering based on the port number of the sender

 access-list 101 permit tcp 172.16.3.0 0.0.0.255 eq 21 172.16.1.0 0.0.0.255 access-list access-list-number {deny | permit} {tcp | udp} source source-wildcard [operator [port]] destination destination-wildcard [operator [port]] [established] [log] 

Extended lists should be placed as close as possible to the sender of the packets.

Named Lists

Command to configure a named standard or advanced access control list configuration with access to the access control list configuration mode

 ip access-list {standard | extended} name 

Access control list configuration mode command to enter information about matching criteria and actions related to a named access control list that maps to TCP segments

 {deny | permit} source [source wildcard] [log] {deny | permit} tcp source source-wildcard [operator [port]] destination destination-wildcard [operator [port]] [log] 

Editing access control lists using sequence numbers

Deleting a row with a sequence number of 20:

 no 20 

Insert a new first row with number 5:

 5 deny 10.0.0.1 

Before making changes to the access control list, delete it in the interface in which it is specified ( no ip access-group ).
If lists are created in a text editor (as recommended), then it may be convenient to start each file with the command no access-list number followed by the configuration commands in the access control list. In this case, after each editing of the file, it is enough to copy and paste the contents of the entire file; the first line will delete the entire existing access control list, and the remaining instructions will recreate the new list.

NAT. Network Address Translation. Network Address Translation

NAT Addressing Terms

Term	Value
Inside local	IP address assigned to a host on a private enterprise network
Inside global	To represent an internal node when a packet is forwarded through an external network. The NAT router changes the sender's address in the packet from internal local to internal global.
Outside global	The real IP address assigned to a node located outside the corporate network, usually on the Internet.
Outside local	NAT can broadcast external IP addresses. When a NAT router forwards a packet from an internal network to an external one using NAT to change the external address, the IP address representing the external node as the destination IP address in the packet header is called the external local address.

NAT Overload with Port Translation (PAT)

Allows NAT translations to support multiple clients with just a few public IP addresses.

NAT dynamic translation table with overload

Inside local	Inside global
10.1.1.1:1024	200.1.1.2:1024
10.1.1.2:1024	200.1.1.2:1025
10.1.1.3:1025	200.1.1.2:1026

Configuring static address translation

1. Using an interface subcommand

 ip nat inside 

Configure the interfaces so that they are inside the NAT scheme.
2. Using an interface subcommand

 ip nat outside 

Configure the interfaces so that they are located in the outer part of the NAT scheme.
3. Configure static transforms using the global configuration command

 ip nat inside source static inside-local inside-global 

Configuring Dynamic Address Translation

1. Using an interface subcommand

 ip nat inside 

Configure the interfaces so that they are inside the NAT scheme.
2. Using an interface subcommand

 ip nat outside 

Configure the interfaces so that they are located in the outer part of the NAT scheme.
3. Configure an ACL list corresponding to packets arriving at the internal interfaces for which NAT translation should be applied.
4. Using the global configuration command, specify a pool of registered addresses:

 ip nat pool name first-address last-address mask subnet-mask 

5. Enable dynamic translation by specifying the ACL access list and address pool:

 ip nat source list acl-number pool pool-name 

Configuring NAT Overload (PAT)

The same actions as in paragraphs. 1-4 for configuring dynamic translation

 5. ip nat source list acl-number interface type number overload 

IPv6

IPv6 routing protocols

Routing protocol	Defined by	Remarks
RIPng (RIP Next Generation)	RFC	Link to "Star Trek: the Next Generation."
OSPFv3 (OSPF version 3)	RFC	OSPFv2 is used for IPv4
EIGRPv6 (EIGRP for IPv6)	Cisco	Cisco owns the rights to the EIGRP protocol, but also published it as an informative RFC
MP BGP-4 (Multiprotocol BGP version 4)	RFC	BGP version 4 was created highly extensible, IPv6 support was added as an add-on to MP BGP-4

IPv6 address types

Type of	First hex
Global unicast	2 or 3
Unique local	Fd
Multicast	FF
Link-Local	FE80

Global unicast

Set by IANA, RIR or ISP (P bits)	Set by Local Engineer (S bits)	(I bits)
Global Routing Prefix	Subnet	Interface ID

P + S + I = 128

 : 2001:DB8:1111:4::1 

Unique Local Unicast

8 bits	40 bits	16 bits	64 bits
Fd	Global ID (Pseudo-Random)	Subnet	Interface ID
Subnet ID

 : FD00:1:1:0001::1 

Link-Local

10 bits	54 bits	64 bits
FE80 / 101111111010	All 0	Interface ID

Multicast

Address Usage	IPv6	IPv4
All IP Channel Nodes	FF02 :: 1	Subnet Broadcast Address
All channel routers	FF02 :: 2	Not
OSPF protocol messages	FF02 :: 5, FF02 :: 6	224.0.0.5, 224.0.0.6
RIP protocol messages (version 2 and NG)	FF02 :: 9	224.0.0.9
EIGRP messages	FF02 :: A	224.0.0.10
DHCP Forwarding Agents (routers that perform service message forwarding to the DHCP server)	FF02 :: 1: 2	Not

Special addresses:

:: 1 (analog 127.0.0.1)
:: (unknown, all zeros)

Address format with interface identifier and EUI-64

48 bits	16 bits	64 bits
Subnet prefix	Subnet	Interface ID
		1st Half of MAC Invert 7th Bit, 1st Byte (Reading Left to Right)	FFFE	2nd Half of MAC
Defined by Configuration		Calculated by Router Using EUI-64

Information sources:
1. Odom U. CCENT / CCNA ICND1 100-101 Official Cert Guide, 2013
2. Odom U. Official guide to the preparation for certification exams CCENT / CCNA ICND1, 2nd ed .: Trans. from English - M .: OOO “I.D. Williams, 2009, i.e. This is to the old 640-822,
3. Odom U. Official guide to preparing for the certification exam CCNA ICND2, 2nd ed .: Trans. from English - M .: OOO “I.D. Williams, 2009, i.e. this is to the old 640-816 and 640-802,
4. Lammle T. CCNA Cisco Certified Network Associate Study Guide, 7th edition, 2011
5. Transmission of Unicast, Broadcast and Multicast traffic.
6. KDPV taken from here

Useful links: