TCPIP 4 ARP Address Resolution Protocol 4 1

TCP/IP 통신망 특론 제 4장 주소변환 프로토콜 (ARP : Address Resolution Protocol)

4. 1 ARP개 요 (cont’d) 32 -비트 인터넷 주소 ARP RARP 48 -비트 이더넷 주소 Computer Network Lab. 4

Host이름 4. 2 예(cont’d) % ftp bsdi를 입력 Resolver Host이름 FTP IP 주소로 연결설정 TCP IP IP 데이터그램을 IP 주소로 보냄 ARP Ethernet Driver ARP Request (Ethernet Broad Cast) Ethernet Driver ARP Reply (IP주소와 하드웨어 주소) ARP • ftp 호스트 명을 입력 했을 때 ARP동작 Computer Network Lab. IP TCP 7

4. 5 ARP 예 n 일반적인 예 tcpdump 출력 1 0. 0 0: 0: c 0: 6 f: 2 d: 40 ff: ff: ff: ff arp 60: arp who-has svr 4 tell bsdi % arp -a 2 0. 002174 (0. 0022) 0: 0: c 2: 9 b: 26 0: 0: c 0: 6 f: 2 d: 40 arp 60: arp reply svr 4 is-at 0: 0: c 2: 9 b: 26 bsdi % telnet svr 4 discard 3 0. 002831 (0. 0007) 0: 0: c 0: 6 f: 2 d: 40 0: 0: c 2: 9 b: 26 ip 60: Trying 140. 252. 13. 34… dsdi. 1030 > svr. discard: s 596459521: 596459521 (0) Connected to svr 4. Escape character is `^]` win 4096 <mss 1024> [tos 0 x 10] 4 0. 007834 (0. 0050) . ^] svr. discard > dsdi. 1030: s 3562228225: 3562228225 (0) Telnet> quit Connection closed. 0: 0: c 0: 9 b: 26 0: 0: c 0: 6 f: 2 d: 40 ip 60: ack 596459522 win 4096 <miss 1024> 5 0. 009615 (0. 0018) 0: 0: c 0: 6 f: 2 d: 40 0: 0: c 2: 9 b: 26 ip 60: bsdi. 1030 > svr 4. discard: . Ack 1 win 4096 [tos 0 x 10] Computer Network Lab. 11

참고 (그림 2. 1) IEEE 802. 2/802. 3 캡슐화(RFC 1042)와 이더넷 캡슐화(RFC 894) IEEE 802. 2/802. 3 Encapsulation(RFC 1042) 802. 3 MAC 802. 2 LLC dest addr src addr leng 6 6 2 DSAP AA SSAP AA 1 1 802. 2 SNAP cntl 03 1 org code 00 type 3 2 type 0800 2 type 0806 2 type 0835 Ethernet Encapsulation (RFC 894) dest addr src addr 6 6 2 data CRC 38 -1492 4 IP datagram 38 -1492 ARP request/reply 28 RARP request/reply 28 PAD 10 46 -1500 bytes data type 2 46 -1500 type 0800 46 -1500 ARP request/reply 2 type 0835 4 IP datagram 2 type 0806 CRC 28 RARP request/reply 2 Computer Network Lab. 28 PAD 18 12

4. 5 ARP 예 (cont’d) n 존재하지 않는 호스트로의 ARP 요구 Bsdi % date; telnet 140. 252. 13. 36; date Sat Jan 30 06: 46: 33 MST 1993 Trying 140. 252. 13. 34. . . Telnet : Unable to connect to remote host: Connection time out Sat Jan 30 06: 47: 49 MST 1993 bsdi % arp -a ? (140. 252. 13. 36) at (incomplete) tcpdump 출력 1 0. 0 arp who-has 140. 252. 13. 36 tell bsdi 2 5. 509. 069 ( 5. 5091) arp who-has 140. 252. 13. 36 tell bsdi 3 29. 509745 (24. 0007) arp who-has 140. 252. 13. 36 tell bsdi Computer Network Lab. 13

gemini ARP request for 140. 252. 1. 29 Ethernet, subnet 140. 252. 1. 183 ARP reply 140, 252, 1 netb Telebit Net. Blazer router configured to act as proxy ARP agent for sun mode m SLIP (dialup) mode m 140. 252. 1. 29 slip SLIP. 65 . 66 bsdi. 35 Computer Network Lab. sun. 33 svr 4. 34 Ethernet 140. 252. 13 16

4. 8 ARP 명령어 ARP - a : 모든 엔트리를 보임 Bsdi % arp -a sun (140. 252. 13. 33) at 8: 0: 20: 3: f 6: 42 svr 4 (140. 252. 13. 34) at 0: 0: c 2: 9 b: 26 ARP - d : 엔티티의 삭제 ARP - s : 엔트리 추가 • temp : 캐시로부터 타임 아웃 • pub : ARP 대행자 기능 Computer Network Lab. 20