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21 ARP 21.1 ( A R P ) I P 48 bit A R P I P 48 bit A R P RFC 826 Plummer 1982] I P I A R A R P I A R P I P A R P I A R P N e t / 3 A R 1 4 A R P 21.2 ARP N e t / 3 A R P A R P 21-1 A R P b s d i A R P I f n e t i f a d d r i n _ i f a d d r 3-32 6-5 3 6 i f a d d r s o c k a d d r _ d l i n _ i f a d d r 1) l l i n f o _ a r p A R P l l i n f o _ a r p l a _ p r e v l a _ n e x t A R P 5 2) I P (r t e n t r y ) l l i n f o _ a r p l a _ r t r t e n t r y r t e n t r y r t _ l l i n f o l l i n f o _ a r p s u n ( 140. 252. 13. 33 ) s v r 4( 140. 252. 13. 34 ) b s d i( 140. 252. 13. 35 ) l l i n f o _ a r p 18-2 3) l l i n f o _ a r p ( 140. 252. 13. 32 ) r t _ f l a g s C IP i n _ i f i n i t ( 6-19 ) r t i n i t ( H ) b s d i

21 A R P 543 A R P ( L ) 4) r t e n t r y r t _ g a t e w a y s o c k a d d r _ d l s d l _ a l e n 6 s o c k a d d r _ d l 5) r t _ i f p i f n e t l e _ s o f t c[ 0 ] b s d i l o i f r t _ i f p. i f _ o u t p u t 21-1 ARP

544 TCP/IP 2 6) i n _ i f a d d r ( 6-8 i n _ i f a d d r i f a d d r t _ i f a i f a d d r ) l e 0 I P I P i n _ i f a d d r r t _ i f p r t _ i f a 7) l a _ h o l d m b u f I P A R P A R P m b u f l a _ h o l d A R P l a _ h o l d m b u f I P 8) r t _ m e t r i c r m x _ e x p i r e A R P ( 20 ) A R P 4.3BSD Reno 4.3BSD Reno N e t / 2. 4. 4 B S D A R P A R A R P N e t / 2 A R P I m b u f ( 21-1 l a _ h o l d ) N e t / 3 21.3 21-2 9 A R P C net/if arp.h a r p h d r netinet/if ether.h n e t i n e t / i f _ e t h e r. d A R P 21-2 2 1-3 A R P A R 19 21.3.1 10 21-4 21.3.2 A R P a r p _ i n u s e a r p _ a l l o c a t e d 21-4 A R P A R n e t s t a t arp -a A R P s y s c t l 19-36 21-5 18-2 224. 0. 0. 1 L a r p R T F _ L L I N F O A R P i n c o m p l e t e p e r m a n e n t

21 A R P 545 arp ARP / ARP 5 IP RTM_ADD RTF_UP RTF_CLONING ifa_rtrequest 21-3 ARP l l i n f o _ a r p struct llinfo_arp l linfo_arp a r p i n t r q struct ifqueue A R P a r p t _ p r u n e I n t A R P ( 5 ) a r p t _ k e e p I n t A R P ( 20 ) a r p t _ d o w n I n t A R P ( 20 ) a r p _ i n u s e I n t A R P a r p _ a l l o c a t e d I n t A R P a r p _ m a x t r i e s I n t I P A R P ( 5 ) a r p i n i t _ d o n e I n t u s e l o o k b a c k i n t ( ) 21-4

546 TCP/IP 2 21-5 18-2 arp -a 21.3.3 SNMP 1 2 5. 8 SNMP MIB A R P M I B - I I ( I P ) N e t / 2 N e t / 3 A R P A R P S N M P I P index = <i p N e t To M e d i a I f I n d e x>. <i p N e t To M e d i a N e t A d d re s s> i p N e t T o M e d i a I f I n d e x i f _ i n d e x i f I n d e x i p N e t T o M e d i a P h y s A d d r e s s r t _ g a t e w a y i p N e t T o M e d i a N e t A d d r e s s r t _ k e y I P i p N e t T o M e d i a T y p e r t _ f l a g s 1 = 2 = 3 = 4 = ( ) 21-6 IP i p N e t T o M e d i a T a b l e 2 1-6 M I B - I I I P i p N e t T o M e d i a T a b l e i f n e t 0 21.4 ARP A R P 21-7 6 bytes op ARP IP IP ARP 21-7 A R P e t h e r _ h e a d e r a r p h d 5 A R P e t h e r _ a r p a r p h d r a r p h d r 21-8 21-7 4

21 A R P 547 21-8 a r p h d r A R P / 2 1-9 e t h e r _ a r p a r p h d r I P A R P 48 bit 32 I P 21-9 e t h e r _ a r p A R P l l i n f o _ a r p 21-10 A R P 21-1 A R P 21-10 llinfo_arp N e t / 2 A R P A R P N e t / 3 A R P A R P A R A R P 104-106 i n s q u e r e m q u e l a _ r t

548 TCP/IP 2 r t _ l l i n f o l a _ r t 107 A R P I P A R P A R P l a _ h o l d l a _ h o l d 108-109 l a _ a s k e d I P 21-24 A R P 110 r t _ m e t r i c s r m x _ e x p i r e A R P 0 A R P 21.5 a r p w h o h a s a r p w h o h a s a r p r e s o l v e A R P 21-11 I P ( 6-28 SIOCSIFADDR ioctl) I P a r p w h o h a s a r p r e q u e s t 2 1-11 a r p w h o h a s A R P 196-202 a r p c o m ( 3-26 ) l e _ s o f t c ( 3-20 a c _ i p a d d r I P SIOCSIFADDR ioctl ( 6-28 ) a c _ e n a d d r a d d r A R P I P a d d r a c _ i p a d d r a r p r e q u e s t I P I P 21.6 a r p r e q u e s t a r p r e q u e s t a r p w h o h a s A R P A R P A R P e t h e r _ o u t p u t e t h e r _ o u t p u t m b u f 21-7 I P ( 2 1-3 i p _ o u t p u t e t h e r _ o u t p u t ) s a _ f a m i l y A F _ U N S P E C e t h e r _ o u t p u t

21 A R P 549 e t h e r _ o u t p u t a r p r e s l o v e 21-3 a r p r e q u e s t e t h e r _ o u t p u t e t h e r _ o u t p u t a r p r e s o l v e 2 1-12 m b u f s o c k a d d r e h e a 1 14 (72 ) (28 ) 21-12 a r p r e q u e s t s o c k a d d r m b u f 2 1-13 a r p r e q u e s t 21-13 a r p r e q u e s t A R P

550 TCP/IP 2 1. m b u f 21-13 ( ) 209-223 m b u f M H _ A L I G N 2 8 e t h e r _ a r p m b u f m _ d a t a m b u f e t h e r _ o u t p u t 14 m b u f 2. 224-226 e a e h e t h e r _ a r p 0 b z e r o 0 8 3. 227-229 E T H E R T Y P E _ A R P 21-14 E T H E R T Y P E _ I P 0 x 0 8 0 0 I P E T H E R T Y P E _ A R P 0 x 0 8 0 6 A R P E T H E R T Y P E _ R E V A R P 0 x 8 0 3 5 A R P E T H E R T Y P E _ I P T R A I L E R S 0 x 1 0 0 0 ( ) 21-14 RARP I P R A R P T C P / I P 1 5 R A R P 4. A R P 230-237 e t h e r _ a r p A R P A R P H R D _ E T H E R 1 6 4 I P a r p _ p r o 21-14 I P ( 0 x 800 ) 21-15 A R P R A R 5. s o c k a d d r 238-241 s a _ f a m i l y A P _ U N S P E C s a _ m e m b e r 1 6 e t h e r _ o u t p u t

21 A R P 551 A R P O P _ R E Q U E S T 1 A R P A R P O P _ R E P L Y 2 A R P A R P O P _ R E V R E Q U E S T 3 R A R P A R P O P _ R E V R E P L Y 4 R A R P 21-15 ARP 21.7 a r p i n t r 4-13e t h e r _ i n p u t E T H E R T Y P E _ A R P N E T I S R _ A R P A R a r p i n t r q a r p i n t r 21-16 21-16 a r p i n t r A R P / 3 1 9-3 4 3 w h i l e a r p h d r E T H E R T Y P E _ I P E T H E R T Y P E _ I P T R A I L E R S i n _ a r p i n p u t i f a r p h d r a r p h d

552 TCP/IP 2 21.8 i n _ a r p i n p u t a r p i n t r A R P / A R P 1) I P A R P A R P I 2) A R P A R P s o c k a d d r _ d l A R P a r p r e q u e s t A R P I P 3) A R P I P N e t / 3 ( i n _ a r p i n o u t A R P ) 4) A R P A R P A R P A R P 5 ). A R P A R A R P I P A R P 1 4. 6 A R P N e t / 3 A R P A R P a r p I P p u b 21-20 21-12 i n _ a r p i n p u t 21-17 358-375 e t h e r _ a r p (a r p _ i n t r ) e a A R P ( ) o p I P i s a d d r i t a d d r 1. I P 376-382 I n t e r n e t (i n _ i f a d d r 6-5 ) I P i f n e t ( m b u f ) f o r I P I P I I P 383-384 m a y b e _ i a 0 I P o u t( 2 1-19 ) m b u f A R P I

21 A R P 553 385 m a y b e _ i a 0 I P I P I P m y a d d r I P ( ) m y a d d r I P I 21-17 i n _ a r p i n p u t 2 1-18 i n _ a r p i n p u t 21-18 i n _ a r p i n p u t

554 TCP/IP 2 2. 3 8 6-3 8 8 3 8 9-3 9 5 3. I P 396-402 I P m y a d d r I P I P m y a d d r r e p l y( 2 1-19 ) A R P I P 2 1-19 i n _ a r p i n p u t 21-19 i n _ a r p i n p u t A R P A R 4. I P 403 a r p l o o k u p A R P I (i s a d d r) A R P I P I P A R P 1 A R P 0 A R P A R P A R P A R P 0 A R P ( ) l l i n f o _

21 A R P 555 a r p 5. 404 i f 1) A R P A R ( l a ) 2) ARP (r t) 3) r e _ g a t e w a y s o c k a d d r _ d l A R P I P 6. 405-408 (s d l _ a l e n) 0 A R P A R P I P 7. 409-410 r t _ g a t e w a y s o c k a d d r _ d l s o c k a d d r _ d l (s d l _ a l e n) 6 A R P ( 21-3 ) 8. A R P 4 1 1-4 1 2 2 0 (a r p t _ k e e p) a r p A R P A R P 0 21-24 A R P ( A R P ) 0 413-414 R T F _ R E J E C Tl a _ a s k e d 0 a r p r e s o l v e A R P 415-420 A R P A R P m b u f mbuf ( 21-1 ) m b u f A R P e t h e r _ o u t o u t a r p r e s o l v e m b u f 9. A R P 421-426 A R P i n _ a r p i n p u t 21-20 A R P A R P 1) 2) A R P A R P A R P 10.

556 TCP/IP 2 427-432 I P m y a d d r ( ) a r p c o m A R P e l s e 21-20 in_arpinput A R P 11. A R P 433-437 A R P a r p l o o k u p 0 S I N _ P R O X Y S I N _ P R O X Y 1 ( A R P ) o u t m b u f 12. 437-442 A R P A R A R P I P A R P A R P a r p p u b I P ( ) A R P 13. A R P 443-444 A R P I P I i t a d d r

21 A R P 557 I P ( 21-18 ) 445-446 A R P A R P O P _ R E P L Y E T H E R T Y P E _ I P E T H E R T Y P E _ I P T R A I L E R S a r p i n t r (trailer encapsulation) 14. s o c k a d d r 447-452 s o c k a d d r 14 21-12 45 3-4 5 5 A R P 21.9 A R P A R P 21-1 21-10 # d e f i n e r m x _ e x p i r e A R P 21.9.1 a r p t i m e r 21-21 5 A R P 1. 21-21 a r p t i m e r 5 A R P 80 a r p _ r t r e q u e s t a r p t i m e r a r p t i m e 5 (a r p t _ p r u n e) 2. A R P 81-86 A R P ( ) a r p t f r e e r t _ e x p i r e 21.9.2 a r p t f r e e 21-22 a r p t f r e e a r p t i m e r l l i n f o _ d l

558 TCP/IP 2 A R P 1. ( ) 467-473 0 r t _ g a t e w a r y s o c k a d d r _ d l a r p t f r e e 1) 0 2) l a _ a s k e d 0 3) R T F _ R E J E C T s d l _ a l e n 0 A R P 21-22 a r p t f r e e A R P 2. 474-475 r t r e q u e s t 21. 13 a r p _ r t r e q u e s t a r p _ r t r e q u e s t A R P m b u f ( l a _ h o l d ) l l i n f o _ a r p 21.10 a r p r e s o l v e 4-16 e t h e r _ o u t p u t a r p r e s o l v e I P a r p r e s l o v e 1 I P a r p r e s o l v e 0 a r p s o l v e l l i n f o _ a r p l a _ h o l d (h e l d) I P A R A R P I P a r p r e s o l v e A R P A R A R P I I P e t h e r _ o u t p u t 11. 9 A R P 21-23 a r p r e s o l v e

21 A R P 559 252-261 d s t s o c k a d d r _ i n I P ( 6 ) 21-23 a r p r e s o l v e A R P 1. 262-270 m b u f M _ B C A S T 1 M _ M C A S T E T H E R _ M A P _ I P _ M U L T I C A S T( 1 2-6 ) D 2. l l i n f o _ a r p 271-276 l a l l i n f o _ a r p a r p l o o k u p I P 1 a r p l o o k u p A R P 0 A R P 277-281 r t l a a r p l o o k u p r t l a 0 2 1-24 a r p r e s o l v e A R P A R P

560 TCP/IP 2 21-24 a r p r e s o l v e A R P A R 3. A R P 282-291 A R P A R 1) ( 0 ) 2) r t _ g a t e w a y s d l _ f a m i l A F _ L I N K 3) (s d l _ a l e n) 0 a r p t f r e e A R P s d l _ a l e n 0 s o c k a d d r _ d l d e s t e n 1 4. I P 292-299 A R P A R P l a _ h o l d m b u f l a _ h o l d A R P A R P I I P l a _ h o l d N F S N F S 8500 I P 6 A R P A R P i p _ o u t p u t e t h e r _ o u t p u t 5

21 A R P 561 A R P N F S 6 5. A R P A R 300-314 RFC 1122 A R P A R P A R P N e t / 3 A R P Net/3 A R P 5 A R P ( 5 ) R T F _ R E J E C T 1 20 e t h e r _ o u t p u t 2 0 I P E H O S T D O W N E H O S T U N R E A C H( 4-15 ) 20 a r p r e s o l v e A R P 0 ( ) R T F _ R E J E C T A R P l a _ a s k e d A R P 0 ( ) A R P A R ( t i m e _ t v _ u s e c ) l a _ a s k e d 5 (a r p _ m a x t r i e s) 1 5 a r p w h o h a s A R P 5 A R P R T F _ R E J E C T 1 20 l a _ a s k e d 0 2 1-25 a r p r e s o l v e e t h e r _ o u t p u t A R P ARP ARP ARP ARP ARP RTF_REJECT EHOSTDOWN ARP 21-25 A R P 26 10 3 6 0. 5 I P 1 ~ 52 A R P A R P 1 l a _ a s k e d 0 l a _ h o l d 1 r t _ e x p i r e ( 10 ) l a _ a s k e d 1 A R P 0 2 1 l a _ h o l d 2 r t _ e x p i r e ( 10 ) A R P 0 3 2 l a _ h o l d 3 ( 11 ) r t _ e x p i r e( 10 ) r t _ e x p i r e 11 l a _ a s k e d 1 5 A R P l a _ a s k e d 2 4 3 l a _ h o l d 4 r t _ e x p i r e

562 TCP/IP 2 ( 11 ) 0 5 ~ 10 9 A R P l a _ a s k e d 5 11 10 l a _ h o l d 11 ( 15 ) r t _ e x p i r e( 14 ) r t _ e x p i r e 15 l a _ a s k e d 5 A R P R T F _ R E J E C T 1 r t _ e x p i r e 35 ( 20 ) l a _ a s k e d 0 12 e t h e r _ o u t p u t R T F _ R E J E C T 1 r t _ e x p i r e( 35 ) E H O S T D O W N ( i p _ o u t p u t) 13 5 0 E H O S T D O W N 51 R T F _ R E J E C T 1 ( 35 ) r t _ e x p i r e( 35 ) a r p r e s o l v e 5 5 A R P 20 A R P 2 1. 11 a r p l o o k u p a r p l o o k u p r t a l l o c l I n t e r n e t A R P 3 a r p l o o k u p 1) i n _ a r p i n p u t A R P I P A R 2) i n _ a r p i n p u t A R P A R 3) a r p r e s o l v e I P A R P a r p l o o k u p l l i n f o _ a r p a r p l o o k u p I P A R P A R P I n t e r n e t s o c k a d d r _ i n a r p 21-26 A R P 21-26 s o c k a d d r _ i n a r p 111-119 8 s o c k a d d r _ i n s i n _ f a m i l y A F _ I N E T 8

21 A R P 563 s i n _ s r c a d d r s i n _ t o s s i n _ o t h e r s i n _ o t h e r S I N _ P R O X Y( 1 ) 2 1-27 a r p l o o k u p 21-27 a r p l o o k u p A R P 1. s o c k a d d r _ i n a r p 480-489 s i n _ a d d r I P p r o x y 0 s i n _ o t h e r S I N _ P R O X Y 0 2. 490-492 r t a l l o c l I n t e r n e t I P c r e a t e 0 0 ( ) 3. 493 A R P r t _ r e f c n t A R P 494-499 R T F _ G A T E W A Y R T F _ L L I N F O r t _ g a t e w a y A F _ L I N K a r p t n e w N e t / 2 A R P r t a l l o c l R T F _ C L O N I N G a r p _ r t r e q u e s t ( 21. 13 ) r t r e q u e s t 21.12 A R P N e t / 3 A R P A R a r p p u b

564 TCP/IP 2 A R P a r p _ r t r e q u e s t ( 21-28 ) R T F _ A N N O U N C E 1 A R P I A R 0 x f f f f f f f f S I N _ P R O X Y 1 21-27 r t a l l o c l 21-20 a r p l o o k u p S I N _ P R O X Y H 1 A R P A R H 1 A R P A R P ( H 1 ) arp -a p u b l i s h e d A R P ( ) sockaddr_inarp ( 2 1-26 ) s i n _ o t h e r S I N _ P R O X Y 12 I n t e r n e t ( 1 8-39 ) 8 S I X _ P R O X Y a r p l o o k u p r t a l l o c l s i n _ o t h e r S I N _ P R O X Y S I N _ P R O X A R P A R P A R P H D 1) H S H D A R P H S H D 2) 3) HS H D 4) H D H H n e t b A R P 1 4.6 arp - a published (proxy only) 21.13 a r p _ r t r e q u e s t 2 1-3 A R P A R 1) a r p l o o k u p r t a l l o c l A R P A R P R T F _ C L O N I N G ( ) R T F _ C L O N I N G r t a l l o c l R T M _ R E S O L V E r t r e q u e s t 1 8-2 140. 252. 13. 33 1 40. 252. 13. 34 140. 252. 13. 32 2) a r p t f r e e R T M _ D E L E T E r t r e q u e s t A R P a r p A R P a r

21 A R P 565 R T M _ R E S O L V E R T M _ D E L E T E R T _ G E T r t r e q u e s t r t a l l o c l I P r t i n i t r t r e q u e s t R T M _ A D D R T F _ U P R T F _ C L O N I N G 18-2 140 252 13 32 19 i f a d d r (i f a _ r t r e q u e s t ) 6-17 i n _ i f i n i t a r p _ r t r e q u e s t A R P a r p _ r t r e q u e s t a r p _ r t r e q u e s t A R P a r p _ r t r e q u e s t l l i n f o _ a r p R T M _ D E L E T E a r p _ r t r e q u e s t l l i n f o _ a r p 2 1-28 a r p _ r t r e q u e s t 21-28 a r p _ r t r e q u e s t R T M _ A D D

566 TCP/IP 2 1. ARP timeout 21-28 ( ) 92-105 a r p _ r t r e q u e s t ( I P ) t i m e o u t a r p t i m e r A R P 5 a r p t i m e r t i m e o u t 2. 106-107 R T F _ G A T E W A Y R T F _ G A T E W A Y A R P 108 s w i t c h R T M _ A D D R T M _ R E S O L V E RTM_DELETE ( ) 3. RT M _ A D D 109 R T M _ A D D a r p A R P r t i n i t I P ( 2 1-3 ) 4. 110-117 R T F _ H O S T ( ) 1 R T F _ C L O N I N G / e t c / n e t s t a r t route add -net 224.0.0.0 -interface bsdi 18-2 R T F _ C L O N I N G 5. 118-126 R T F _ C L O N I N G(i n _ i f i n i t ) r t i n i t r t _ s e t g a t e s o c k a d d r _ d l r t _ g a t e w a y 21-1 1 40. 252. 13. 32 s d l _ f a m i l y s d l _ l e n n u l l _ s d s d l _ t y p e( I F T _ E T H ER ) s d l _ i n d e x i f n e t s d l _ a l e n 0 127-128 b r e a k r m x _ e x p i r e 21-1 l l i n f o _ a r p a r p t i m e r s o c k a d d r _ d l r t _ g a t e w a y R T M _ R E S O L V E r t r e q u e s t

21 A R P 567 n e t s t a t s d l _ i n d e x l i n k # n 18-2 6. A R P 130-135 R T F _ A N N O U N C E a r p p u b (1) s o c k a d d r _ i n a r p s i n _ o t h e r S I N _ P R O X Y ( 2 ) R T F _ A N N O U N C E R T F _ A N N O U N C E a r p r e q u e s t A R P A R I I P 136 R T M _ R E S O L V E c a s e 2 1-29 a r p _ r t r e q u e s t R T M _ R E S O L V E r t a l l o c l R T F _ C L O N I N G r t a l l o c l (a r p l o o k u p c r e a t e ) 0 l l i n f o _ a r p 21-29 a r p _ r t r e q u e s t R T M _ R E S O L V E

568 TCP/IP 2 7. s o c k a d d r _ d l 21-29 ( ) 137-144 r t _ g a t e w a y s o c k a d d r _ d l s a _ f a m i l y s a _ l e n ( I F T_E T H E R) s o c k a d d r _ d l 8. 145-146 l l i n f o _ a r p l a a r p _ r t r e q u e s t l l i n f o _ a r p b r e a k 9. l l i n f o _ a r p 147-158 l l i n f o _ a r p r t _ l l i n f o a r p _ i n u s e a r p _ a l l o c a t e d 1 l l i n f o _ a r p 0 l a _ h o l d l a _ a s k e d 0 159-161 r t l l i n f o _ a r p R T F _ L L I N F O 18-2 A R P 140. 252. 13. 33 1 40. 252. 13. 34 1 40. 252. 13. 35 L 240. 0. 0. 1 a r p ( 1 9-36 ) i n s q u e l l i n f o _ a r p A R P r t r e q u e s t ( ) a r p _ r t r e q u e s t l l i n f o _ a r p A R P a r p r e s o l v e a r p l o o k u p a r p _ r t r e q u e s t ( 21-3 ) a r p r e s o l v e A R P 10. 162-173 4. 4 B S D ( ) 21-1 I P ( 140. 252. 13. 35 ) i f I P 11. 174-176 0 a r p c o m r t _ g a t e w a y s o c k a d d r _ d l 12. 177-178 u s r l o o p b a c k 0 ( 1 ) 4. 4 B S D / e t c / n e t s t a r t route add 140.252.13.35 127.0.0.1 I P 4. 4 B S D

21 A R P 569 I P A R P I P R T M _ R E S O L L V E a r p _ r t r e q u e s t 21-30 R T M _ D E L E T E 21-3 a r p A R P a r p t f r e e 21-30 arp_rtrequest R T M _ D E L E T E 13. l a 182-183 l a l l i n f o _ a r p b r e a k 14. l l i n f o _ a r p 184-190 a r p _ i n u s e 1 r e m q u e l l i n f o _ a r p r t _ l l i n f o 0 R T F _ L L I N F O A R P m b u f ( A R P ) m b u f l l i n f o _ a r p s w i t c h d e f a u l t R T M _ G E T a r p R T M _ G E T r o u t e _ o u t p u t r t r e q u e s 21-3 R T M _ G E T r t a l l o c l 0 r t a l l o c l r t r e q u e s t 21.14 ARP I P i p _ o u t p u t ( 12-40 ) i p _ o u t p u t ( 8-24 ) I P 18-2 224. 0. 0. 0 f l a g 224 ( l e 0 ) ( 2 25 ~ 239 ) 224. 0. 11 ( ) 224. 0. 0. 0 I P _ M U L T I C A S T _ I F 18-2 224. 0. 0. 0

570 TCP/IP 2 l e 0 a r p r e s o l v e 21-23 E T H E R _ M A P _ I P _ M U L T I C A S T 23 ( 1 2-6 ) A R P A R P A R P 21-5 R T F _ L L I N F O A R P A R P E T H E R _ M A P _ I P _ M U L T I C A S T A R P A R P 18-2 224. 0. 0. 1 r t r e q u e s t r t _ m e t r i c s ( 19-9 ) 21-28 r m x _ e x p i r e R T M _ A D D 224. 0. 0. 1 a r p t i m e r 224. 0. 0. 1 A R P 21.15 A R P I P N e t / 3 BSD A R P l l i n f o _ a r p 21-1 A R P A R P i n _ a r p i n p u t I P A R I P A R A R P N e t / 3 B S D A R P 5 20 A R P 21.1 2 1-17 a c 21.2 p i n g arp -a A R P 21.3 21-19 s d l _ a l e n 6 21.4 N e t / 2 A R P a r p r e s o l v e A R P N e t / 3 21.5 N e t / 2 A R P A R P 3 A R P N e t / 3 N e t / 3 21.6 N e t / 3 A R P

21 A R P 571 21.7 2 1-1 r m x _ e x p i r e 21.8 A R P A R 21.9 21-25 1 C s o c k 500 ms U D P ( - p ) E H O S T D O W N 10 U D P 21-25 11 21.10 A R P A R P