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becool
20210517 (월) 본문
9:33 review
프로토콜 요약
TCP
연결지향, 신뢰성있는 바이트스트림
신뢰성있는 데이터 전송 : 메시지를 성공적으로 수신 했거나 오류가 발생했다는 것을 알리는 것.
신뢰성있고 순서적인 데이터 전송 : Connection Oritented Service 송신측 전송 계층 프로세스와 목적지 전송 계층 프로세스 사이에 연결이라는 논리적 관계가 설정된다는 것
※ TCP 3-way handshake : SYN, SYN-ACK, ACK
TCP를 통한 데이터 전송 전 TCP 세션 연결을 수립하는 과정
체결 established
※ TCP 4-way handshake : FIN ACK, ACK, FIN ACK, ACK (Active close - Passive close)
TCP 세션 연결을 정상 종료하는 과정
TCP 헤더의 구조
Source Port
Destination Port
Sequence Number
Acknowledgement Number
Offset
Reserved
TCP control flags
CWR(Reduced) : Congestion Windows
ECE : ECN echo, Congestion Windows
urg : Urgent data 가 있는경우 1, 없는경우 0
ack : Acknowledgement number 수신 데이터에 대한 응답을 보낼 때 사용하는 플래그
psh : Push 데이터 전송 시 사용하는 플래그
rst : Reset 연결을 강제종료 하거나 리셋시 사용하는 플래그
syn : synchronize TCP 연결 동기화를 위해 사용하는 플래그
fin : TCP 연결을 정상적으로 종료하기 위해 사용하는 플래그
Windows size : 16bit 길이로 수신버퍼의 크기
Checksum : 16bit TCP 세그먼트의 전체 데이터 (TCP 헤더 + 데이터) 오류 체크하기 위한 필드
Urgent Pointer ; 16bit 길이로 Urgent Data가 존재하는 경우 Urgent Data의 끝 부분을 가리키는 Pointer
Options : 가변길이 4bytes 단위
UDP
비연결 지향 프로토콜 (Connectionless Oriented Protocol)
헤더의 크기 : 8bytes
독립적인 제어메시지 사용하지 않음
요청메시지/응답메시지 두가지로 구성
DNS, DHCP, SNMP 등
================================
Packet Tracer
Cisco Systems 사에서 개발한 네트워크 시뮬레이터
www.netacd.com 에서 회원가입, Packet Tracer 7.3.1
스위치 : catalyst 2950 3750 L2 데이터링크부터 L3까지 커버가능한 다양한 모델이 있음.
기본스위치 : L2에서 동작하는 스위치위주로 실습 (2950 : fast ethernet , 2960)
2950-24 : 포트 24개까지 지원
2950-24T : 포트 24개까지 지원 + giga bit 2개의 포트 추가 지원
2960 : giga bit 기본 지원
3750 : L3까지 지원하면서 광슬롯
Connection 전송매체 종류
Straight-Through Cable (=Direct) :
Crossover Cable : 같은 장비들끼리 연결 (pc-pc, switch-switch, hub-hub 등)
Rollover Cable : 제어하고자 할때 네트워크 장비-PC 간 연결 → Terminal Configuration
※ 네트워크 장비에는 별도의 입력장치가 없으므로 PC와 연결(console)을 통하여 세팅
※ RS232 (해당 규격이 사라지는 추세, USB나 USB로 컨버터로 PC와 연결) + 네트워크 장비 콘솔
Serial DCE
Serial DTE
DCE (Data Communication Equipment)
Serial 통신에서 Clock을 생성해주는 장비
CSU/DSU/Modem
DTE (Data Terminal Equipment)
Serial 구간에서 관리하는 네트워크와 연결된 마지막 장비
▶ 패킷 트레이서에서 serial DTE, serial DCE는 먼저 클릭한 쪽과 이끌어서 연결한 쪽 두가지로 나누게됨.
Cisco Systems IOS : Internetwork OS
Cisco 네트워크 장비의 운영체제
Cisco IOS 모드
각각의 모드에서 사용가능한 명령어, 설정 등이 정해져있으므로 각각의 모드에 대한 이해가 필요.
- User Mode : 가장 처음 진입하는 모드. 제한적인 모드 (다른장비와의 통신 테스트 정도만 가능)
- Privileged mode : 특권, 관리자모드. enable로 접근가능 다른 네트워크장비의 설정 확인, 저장 등이 가능
- Global Configuration mode : 네트워크 장비의 전역적 설정을 할 수 있는 모드 (Hostname, Interface 등)
- Interface Mode : Ethernet, FastEthernet, Serial 등 인터페이스를 설정하는 모드
- Line Interface Mode : Console, VTY 등 Line Interface를 설정하는 모드
=== IOS의 명령어 ===
<유저실행모드>
Router>?
Exec commands:
<1-99> Session number to resume
connect Open a terminal connection
disable Turn off privileged commands
disconnect Disconnect an existing network connection
enable Turn on privileged commands
exit Exit from the EXEC
logout Exit from the EXEC
ping Send echo messages
resume Resume an active network connection
show Show running system information
ssh Open a secure shell client connection
telnet Open a telnet connection
terminal Set terminal line parameters
traceroute Trace route to destination
<프리빌리지모드>
Router#?
Exec commands:
<1-99> Session number to resume
auto Exec level Automation
clear Reset functions
clock Manage the system clock
configure Enter configuration mode
connect Open a terminal connection
copy Copy from one file to another
debug Debugging functions (see also 'undebug')
delete Delete a file
dir List files on a filesystem
disable Turn off privileged commands
disconnect Disconnect an existing network connection
enable Turn on privileged commands
erase Erase a filesystem
exit Exit from the EXEC
logout Exit from the EXEC
mkdir Create new directory
more Display the contents of a file
no Disable debugging informations
ping Send echo messages
reload Halt and perform a cold restart
resume Resume an active network connection
rmdir Remove existing directory
send Send a message to other tty lines
setup Run the SETUP command facility
show Show running system information
ssh Open a secure shell client connection
telnet Open a telnet connection
terminal Set terminal line parameters
traceroute Trace route to destination
undebug Disable debugging functions (see also 'debug')
vlan Configure VLAN parameters
write Write running configuration to memory, network, or terminal
<글로벌컨피그레이션 모드>
Router(config)#?
Configure commands:
aaa Authentication, Authorization and Accounting.
access-list Add an access list entry
banner Define a login banner
bba-group Configure BBA Group
boot Modify system boot parameters
cdp Global CDP configuration subcommands
class-map Configure Class Map
clock Configure time-of-day clock
config-register Define the configuration register
crypto Encryption module
default Set a command to its defaults
do To run exec commands in config mode
dot11 IEEE 802.11 config commands
enable Modify enable password parameters
end Exit from configure mode
exit Exit from configure mode
flow Global Flow configuration subcommands
hostname Set system's network name
interface Select an interface to configure
ip Global IP configuration subcommands
ipv6 Global IPv6 configuration commands
key Key management
license Configure license features
line Configure a terminal line
lldp Global LLDP configuration subcommands
logging Modify message logging facilities
login Enable secure login checking
mac-address-table Configure the MAC address table
no Negate a command or set its defaults
ntp Configure NTP
parser Configure parser
policy-map Configure QoS Policy Map
port-channel EtherChannel configuration
priority-list Build a priority list
privilege Command privilege parameters
queue-list Build a custom queue list
radius-server Modify Radius query parameters
router Enable a routing process
secure Secure image and configuration archival commands
security Infra Security CLIs
service Modify use of network based services
snmp-server Modify SNMP engine parameters
spanning-tree Spanning Tree Subsystem
tacacs-server Modify TACACS query parameters
username Establish User Name Authentication
vpdn Virtual Private Dialup Network
vpdn-group VPDN group configuration
Router(config)#line ?
<2-499> First Line number
aux Auxiliary line
console Primary terminal line 콘솔
tty Terminal controller
vty Virtual terminal 원격
x/y/z Slot/Subslot/Port for Modems
Router(config)#line console 0
<인터페이스모드>
Router(config)#interface ?
Dialer Dialer interface
Dot11Radio Dot11 interface
Ethernet IEEE 802.3
FastEthernet FastEthernet IEEE 802.3
GigabitEthernet GigabitEthernet IEEE 802.3z
Loopback Loopback interface
Port-channel Ethernet Channel of interfaces
Serial Serial
Tunnel Tunnel interface
Virtual-Template Virtual Template interface
Vlan Catalyst Vlans
range interface range command
=== IOS의 명령어 실습 ===
Router>enable → Privileged 모드로 전환
Router#show interfaces
Router#show running-config
Router#configure terminal → 글로벌 컨피그레이션 모드로 전환
Enter configuration commands, one per line. End with CNTL/Z.
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname R1 → hostname [NAME] 라우터의 장비 이름을 영구적으로 변경(런타임이 아닌)
R1(config)#interface gigabitEthernet 0/0 → interface + Device : 인터페이스 모드로 전환
R1(config-if)#exit
R1(config)#line console 0 → 라인콘솔 모드
R1(config-line)# exit → 글로벌 컨피그레이션 모드로 전환
R1(config)#exit → priviledged 모드로 전환
R1#
%SYS-5-CONFIG_I: Configured from console by console
disable → user mode로 전환
R1>
※ priviledged mode에서 오타입력. 호스트로 인식하여 접속을 시도 : 접속 시도를 중지할려면 Ctrl + Shift + 6 입력


serial 0/0/0, serial 0/0/1 형태로 추가됨
장비에 전원을 넣고 CLI 탭으로 이동
Router>enable
Router#show interfaces
FastEthernet0/0 is administratively down, line protocol is down (disabled)
Hardware is Lance, address is 00d0.d36d.5401 (bia 00d0.d36d.5401)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Full-duplex, 100Mb/s, media type is RJ45
ARP type: ARPA, ARP Timeout 04:00:00,
Last input 00:00:08, output 00:00:05, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: fifo
Output queue :0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 input packets with dribble condition detected
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
Router#show interfaces
FastEthernet0/0 is administratively down, line protocol is down (disabled)
Hardware is Lance, address is 00d0.d36d.5401 (bia 00d0.d36d.5401)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Full-duplex, 100Mb/s, media type is RJ45
ARP type: ARPA, ARP Timeout 04:00:00,
Last input 00:00:08, output 00:00:05, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: fifo
Output queue :0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 input packets with dribble condition detected
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
FastEthernet0/1 is administratively down, line protocol is down (disabled)
Hardware is Lance, address is 00d0.d36d.5402 (bia 00d0.d36d.5402)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Full-duplex, 100Mb/s, media type is RJ45
ARP type: ARPA, ARP Timeout 04:00:00,
Last input 00:00:08, output 00:00:05, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: fifo
Output queue :0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 input packets with dribble condition detected
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
Serial0/0/0 is administratively down, line protocol is down (disabled)
Hardware is HD64570
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation HDLC, loopback not set, keepalive set (10 sec)
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/0/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
Available Bandwidth 1158 kilobits/sec
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 output buffer failures, 0 output buffers swapped out
0 carrier transitions
DCD=down DSR=down DTR=down RTS=down CTS=down
Serial0/0/1 is administratively down, line protocol is down (disabled)
Hardware is HD64570
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation HDLC, loopback not set, keepalive set (10 sec)
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/0/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
Available Bandwidth 1158 kilobits/sec
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 output buffer failures, 0 output buffers swapped out
0 carrier transitions
DCD=down DSR=down DTR=down RTS=down CTS=down
FastEthernet1/0 is administratively down, line protocol is down (disabled)
Hardware is Lance, address is 000a.41d9.b501 (bia 000a.41d9.b501)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Full-duplex, 100Mb/s, media type is RJ45
ARP type: ARPA, ARP Timeout 04:00:00,
Last input 00:00:08, output 00:00:05, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: fifo
Output queue :0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 input packets with dribble condition detected
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
FastEthernet1/1 is administratively down, line protocol is down (disabled)
Hardware is Lance, address is 000a.41d9.b502 (bia 000a.41d9.b502)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Full-duplex, 100Mb/s, media type is RJ45
ARP type: ARPA, ARP Timeout 04:00:00,
Last input 00:00:08, output 00:00:05, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: fifo
Output queue :0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 input packets with dribble condition detected
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
Vlan1 is administratively down, line protocol is down
Hardware is CPU Interface, address is 0001.4337.c736 (bia 0001.4337.c736)
MTU 1500 bytes, BW 100000 Kbit, DLY 1000000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
ARP type: ARPA, ARP Timeout 04:00:00
Last input 21:40:21, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
1682 packets input, 530955 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicast)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
563859 packets output, 0 bytes, 0 underruns
0 output errors, 23 interface resets
0 output buffer failures, 0 output buffers swapped out
Router(config)#interface fastEthernet 0/0
Router(config-if)#exit
Router(config)#interface FastEthernet 0/1
Router(config-if)#exit
Router(config)#interface FastEthernet 1/0
Router(config-if)#exit
Router(config)#interface FastEthernet 1/1
Router(config-if)#exit
Router(config)#interface Serial 0/0/0
Router(config-if)#exit
Router(config)#interface Serial 0/0/1
Router(config-if)#exit
PC마다 IP 부여하기 : desktop → ip configuration → static → ipv4 address, subnet mask, default gateway, dns 입력 후 저장
각 PC마다 서로 통신되는지 확인 : 토폴리지가 구성되어서 통신이 되는지 확인 desktop → command line → ping [IP]
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