A4_1¶

1. NETWORK INFRASTRUCTURE & ROUTER¶

Thành phần Router¶

CPU, RAM (running-config), Flash, NVRAM (startup-config)
Interfaces: Management (console, miniUSB, aux), LAN (GigaEthernet, FastEthernet), WAN (Serial)

Vai trò Router¶

LAN Segmentation, Routing, Forwarding
Luồng dữ liệu: IP thay đổi theo interface, MAC = interface → default gateway

Loại định tuyến¶

L (Local), C (Connected), S (Static), R (RIP), D (EIGRP), O (OSPF)

2. STATIC ROUTING¶

Ưu/Nhược điểm¶

Ưu: Bảo mật tốt, ít băng thông/CPU, đường đi xác định
Nhược: Khó bảo trì, dễ lỗi cấu hình, không mở rộng tốt

Cấu hình¶

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Router(config)# ip route <destination> <subnet-mask> <next-hop/exit-interface>
Router(config)# ip route 0.0.0.0 0.0.0.0 <gateway>  // Default route

Loại Static Route¶

Standard, Default, Summary, Floating

3. RIP (Distance Vector)¶

Đặc điểm¶

Metric: Hop count (max 15)
Update: 30s, broadcast/multicast
Algorithm: Bellman-Ford

RIPv1 vs RIPv2¶

Tiêu chí	RIPv1	RIPv2
Update address	255.255.255.255	224.0.0.9
VLSM/CIDR	No	Yes
Authentication	No	Yes

Cấu hình¶

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Router(config)# router rip
Router(config-router)# version 2
Router(config-router)# network <network-address>
Router(config-router)# passive-interface <interface>
Router(config-router)# default-information originate

4. OSPF (Link-State)¶

Đặc điểm¶

Algorithm: Dijkstra
Metric: Cost (bandwidth-based)
Hội tụ nhanh, hỗ trợ VLSM/CIDR

Cấu hình¶

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Router(config)# router ospf <process-id>
Router(config-router)# network <ip> <wildcard-mask> area <area-id>
Router(config-router)# passive-interface <interface>

5. VLAN & INTER-VLAN ROUTING¶

Cấu hình VLAN trên Switch¶

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Switch(config)# vlan <vlan-id>
Switch(config-vlan)# name <vlan-name>
Switch(config)# interface <interface>
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan <vlan-id>

Trunk Configuration¶

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Switch(config-if)# switchport mode trunk
Switch(config-if)# switchport trunk allowed vlan <vlan-list>

Inter-VLAN Routing Methods¶

Legacy: Mỗi VLAN = 1 interface vật lý
Router-on-a-Stick: Sub-interface trên trunk
Multilayer Switch: SVI (Switch Virtual Interface)

Router-on-a-Stick¶

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Router(config)# interface g0/0/0.10
Router(config-subif)# encapsulation dot1Q 10
Router(config-subif)# ip address <ip> <mask>

Multilayer Switch¶

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Switch(config)# ip routing
Switch(config)# interface vlan 10
Switch(config-if)# ip address <ip> <mask>
Switch(config-if)# no shutdown

6. DHCP¶

DHCP Process (DORA)¶

Discover (broadcast)
Offer (unicast/broadcast)
Request (broadcast)
ACK (unicast/broadcast)

Router làm DHCP Server¶

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Router(config)# ip dhcp pool <name>
Router(dhcp-config)# network <network> <mask>
Router(dhcp-config)# default-router <gateway>
Router(dhcp-config)# dns-server <dns-ip>
Router(dhcp-config)# lease <days>
Router(config)# ip dhcp excluded-address <start-ip> <end-ip>

Router làm DHCP Relay Agent¶

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Router(config)# interface <interface>
Router(config-if)# ip helper-address <dhcp-server-ip>

7. NAT (Network Address Translation)¶

NAT Types¶

Static NAT: 1-1 mapping
Dynamic NAT: Pool mapping
PAT (Overload): Many-to-One

Cấu hình NAT Overload (PAT)¶

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Router(config)# access-list 1 permit <source-network> <wildcard>
Router(config)# ip nat inside source list 1 interface <outside-interface> overload
Router(config)# interface <inside-interface>
Router(config-if)# ip nat inside
Router(config)# interface <outside-interface>
Router(config-if)# ip nat outside

Port Forwarding (Static NAT)¶

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Router(config)# ip nat inside source static tcp <local-ip> <local-port> <global-ip> <global-port>

8. ACL (Access Control List)¶

Wildcard Mask¶

0 = must match, 1 = don't care
Ví dụ: 192.168.1.0 0.0.0.255 = network 192.168.1.0/24
Keywords: host (0.0.0.0), any (255.255.255.255)

Standard ACL (1-99, 1300-1999)¶

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Router(config)# access-list <1-99> {permit|deny} <source> <wildcard>
Router(config)# interface <interface>
Router(config-if)# ip access-group <acl-number> {in|out}

Đặt gần destination

Extended ACL (100-199, 2000-2699)¶

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Router(config)# access-list <100-199> {permit|deny} <protocol> <source> <wildcard> [operator port] <dest> <wildcard> [operator port]
Router(config-if)# ip access-group <acl-number> {in|out}

Đặt gần source
Protocol: tcp, udp, icmp, ip
Operator: eq (equal), lt (less than), gt (greater than)

ACL Rules¶

1 ACL/protocol/direction/interface
Implicit deny all ở cuối
Top-down processing

9. LINUX ADMINISTRATION¶

User Management¶

Bash

useradd -u <uid> -g <group> -G <groups> -c "comment" -d <home> <username>
passwd <username>
usermod -c "new comment" -d <new-home> -e <expire-date> <username>
userdel -r <username>  # -r xóa cả home directory

Group Management¶

Bash

groupadd -g <gid> <groupname>
groupmod -n <new-name> -g <new-gid> <groupname>
groupdel <groupname>

File Quan Trọng¶

/etc/passwd: User info
/etc/shadow: Encrypted passwords
/etc/group: Group info
/etc/login.defs: Default settings
/etc/default/useradd: Useradd defaults

Network Configuration¶

Bash

# Interface config
ifconfig <interface> <ip> netmask <mask>
ip addr add <ip>/<prefix> dev <interface>
ip link set <interface> up

# Routing
route add default gw <gateway>
ip route add default via <gateway>

# DNS: /etc/resolv.conf
nameserver <dns-ip>

Network Tools¶

Bash

ping <host>              # Test connectivity
netstat -rn              # Routing table
netstat -tln             # Listening TCP ports
dig <domain>             # DNS lookup
host <domain/ip>         # Reverse/forward lookup
ssh <user>@<host>        # Remote login

10. WINDOWS SERVER¶

DHCP Server¶

Scope: Pool IP addresses
Exclusions: Reserved IPs
Reservations: MAC-to-IP binding
Options: Gateway, DNS, lease time

DNS Server¶

Forward Lookup Zone: Name → IP
Reverse Lookup Zone: IP → Name
Record types: A, AAAA, CNAME, MX, PTR

Web Server (IIS)¶

Host multiple websites trên 1 server
Binding: IP, port, hostname

File Services¶

Share folders với permissions
NTFS permissions vs Share permissions

Active Directory (AD DS)¶

Thành phần¶

Domain: Security boundary
OU (Organizational Unit): Container for objects
Objects: Users, Computers, Groups

User/Computer Accounts¶

Domain users vs Local users
Computer accounts trong domain

Groups¶

Security Groups: Assign permissions
Distribution Groups: Email lists
Scope: Domain Local, Global, Universal

Group Policy (GPO)¶

Password policies
Software deployment
Security settings
Apply theo thứ tự: LSDOU (Local, Site, Domain, OU)

VPN Server¶

Remote access cho users
Access network resources qua VPN tunnel

11. NETWORK MANAGEMENT¶

FCAPS Model¶

Fault Management: Phát hiện/sửa lỗi
Configuration Management: Quản lý cấu hình
Accounting Management: Theo dõi usage
Performance Management: Monitor hiệu năng
Security Management: Bảo mật

Components¶

Manager: Thu thập/phân tích data
Agent: Chạy trên thiết bị được quản lý
MIB (Management Information Base): Database info
Protocol: SNMP (Simple Network Management Protocol)

12. VIRTUALIZATION¶

Loại¶

Process VM: Java VM, .NET CLR
System VM: VMware, VirtualBox, Hyper-V

Techniques¶

Full Virtualization: Guest OS không cần sửa
Para-virtualization: Guest OS cần sửa, hiệu năng cao
OS-level: Containers (Docker, LXC)

VMM (Virtual Machine Monitor) / Hypervisor¶

Type 1 (Bare-metal): ESXi, Hyper-V, Xen
Type 2 (Hosted): VMware Workstation, VirtualBox

TIPS THI¶

Các lệnh show quan trọng¶

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show ip interface brief
show ip route
show running-config
show vlan brief
show interfaces trunk
show ip dhcp binding
show ip nat translations
show access-lists

Troubleshooting Steps¶

Physical layer (cables, lights)
Data link (MAC, VLAN)
Network (IP, routing)
Transport (ports, ACL)
Application (services)

Tính Wildcard từ Subnet Mask¶

Wildcard = 255.255.255.255 - Subnet Mask

/24 (255.255.255.0) → 0.0.0.255
/16 (255.255.0.0) → 0.0.255.255