Understanding DNS and DHCP

Giới thiệu về DNS : - Mỗi máy tính, thiết bị mạng tham gia vào mạng Internetđều giao tiếp với nhau bằng địa chỉ IP (Internet Protocol) . Để thuận tiện cho việc sử dụng và dễ nhớ ta dùng tên (domain name) để xác định thiết bị đó. Hệ thống tên miền (Domain Name System) được sử dụng để ánh xạ tên miền thành địa chỉ IP. Vì vậy, khi muốn liên hệ tới các máy, chúng chỉ cần sử dụng chuỗi ký tự dễ nhớ (domain name) như: , ., thay vì sử dụng địa chỉ IP là. | Cisco Systems NETWORKERS 2004 UNDERSTANDING DHCP AND DNS SESSION NMS-1101 NMS-1101 9592_04_2004_c2 2004 Cisco Systems Inc. All rights reserved 1 Agenda Introduction to Names and Addresses Managing Addresses with DHCP Protocol Assignment and Reliability Resolving Names with DNS Protocol Database Reliable Operation New Things NMS-1101 9592_04_2004_c2 2004 Cisco Systems Inc. All rights reserved. 2 2004 Cisco Systems Inc. All rights reserved. Printed in USA. Address Review 128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1 10000000000010010000000000100001 128 9 0 33 IPv4 address 32 bits Decimal 8-bit fields period separation IPv6 address 128 bits Hexadecimal 16-bit fields colon separation 2001 0DB8 0000 0001 02A0 C9FF FE61 1216 NMS-1101 9592_04_2004_c2 2004 Cisco Systems Inc. All rights reserved. 3 Address Hierarchy and Naming ADDRESSES have a topological hierarchy NAMES have a logical hierarchy NOT NECESSARILY ALIGNED WITH EACH OTHER. NMS-1101 9592_04_2004_c2 2004 Cisco Systems Inc. All rights reserved 4 2004 Cisco Systems Inc. All rights reserved. Printed in USA. Subnet Mask Address 10000000000010010000000000100001 Mask 11111111111111111111111100000000 Mask separates network 1 from host 0 part of the address Prefix longest match routing contiguous 1 bits to the left NMS-1101 9592_04_2004_c2 2004 Cisco Systems Inc. All rights reserved Subnets Each range of addresses for hosts defines a subnet . 24 24 is the number of 1 bits in the mask for this address 32-24 8 is the number of bits in host address Within the subnet hosts communicate directly using layer 2 Special meaning for certain host addresses All ones broadcast All zero network NMS-1101 9592_04_2004_c2 2004 Cisco Systems Inc. All rights reserved. 6 2004 Cisco Systems Inc. All rights reserved. Printed in USA. .