네트워크

netfilter, iptables

netfilter - The Packet Filtering Framework for Linux 리눅스 커널 모듈로서 네트워크 패킷을 처리하기 위한 프레임워크이다. netfilter는 패킷 필터링, 네트워크 주소 변환 및 포트 변환을 위한 다양한 기능 및 작업을 제공한다. 이러한 기능은 네트워크를 통해 패킷을 전달하고 패킷이 네트워크의 중요한 위치에 도달하는 것을 방지하는 데 필요한 기능을 제공한다. iptables - Packet Mangling Tool 패킷을 필터링하거나 변환할 수 있는 방화벽 규칙을 정의하기 위한 테이블 기반 시스템을 제공한다. NIC을 거쳐 유입되는 모든 네트워크 패킷을 netfilter에 등록된 룰을 거쳐 제어된다. iptables를 활용하면 특정 조건에 부합하는 패킷을 드랍하거..

[CCNA] CCNA1 - Chapter5

What happens to runt frames received by a Cisco Ethernet switch? In an attempt to conserve bandwidth and not forward useless frames, Ethernet devices drop frames that are considered to be runt (less than 64 bytes) or jumbo (greater than 1500 bytes) frames. Ethernet frame The minimum Ethernet frame is 64 bytes. The maximum Ethernet frame is 1518 bytes. A network technician must know the minimum a..

[CCNA] CCNA1 - Chapter4

reasons for physical layer protocols to use frame encoding techniques to distinguish data bits from control bits to identify where the frame starts and ends A network administrator notices that some newly installed Ethernet cabling is carrying corrupt and distorted data signals. The new cabling was installed in the ceiling close to fluorescent lights and electrical equipment. Which two factors m..

[CCNA] CCNA1 - Chapter3

flow control Flow control allows for this by ensuring that data is not sent too fast for it to be received properly. encapsulation Encapsulation is the process of placing one message format into another message format. An example is how a packet is placed in its entirety into the data field as it is encapsulated into a frame. network protocols Network protocols are implemented in hardware, or so..

[CCAN] CCNA1 - Chapter2

A network administrator needs to keep the user ID, password, and session contents private when establishing remote CLI connectivity with a switch to manage it. Which access method should be chosen? ssh Which command or key combination allows a user to return to the previous level in the command hierarchy? End and CTRL-Z : return the user to the privileged EXEC mode. Ctrl-C : ends a command in pr..

[CCNA] CCNA1 - Chapter1

Intermediary devices Intermediary devices direct path of the data Intermediary devices connect individual hosts to the network Intermediary devices interconnect end devices. Examples of intermediary network devices are: switches and wireless access points (network access) routers (internetworking) firewalls (security). Which two connection options provide an always-on, high-bandwidth Internet co..