4月10日路由题库的几道题

joward

求高手指导，QUESTION 222和QUESTION 202、QUESTION 223和QUESTION 220，好像答案有点问题

+ f5 a) P. l/ E& vQUESTION 222
What’s uRPF checking first when the packet enters the interface ? or when unicast reverse patch forwarding is configured on interinterface.
5 R4 T# E3 \2 ~& xA. it check the ingress access list
B. it check the egress access list
' h6 M1 x8 }9 a/ ?3 R0 @C. Route available in FIB ot it verifies a reverse patch via the fib to the source
D. it verify that the source has a......
6 j- o  G" q/ N& u, y/ k: v% ICorrect Answer: C
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, ^+ h/ x( }6 _/ ~2 ~. t$ _. {QUESTION 202
8 B9 k7 h1 X2 _1 C+ [* l0 sWhen unicast reverse path forwarding is configured on an interface, which action does the interface take first when it receives a packet?
2 H' P: o( u; Q& d$ PA. It check the ingress access list
, S4 C4 x( q2 n' Z8 f5 O0 |. G2 HB. It check the egress access list
C. It verifies that the source has a valid CEF adjacency
D. It verifies a reverse path via the FIB to the source
Correct Answer: A
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& i, f, k6 D# k! a( hQUESTION 223
! d8 r/ b9 Y$ P# N7 S( CTwo scenarios for preventing fragmentation on GRE tunnel(Choose two)
) T8 l1 i+ K5 r: s- r0 P2 YA. TCP MSS
+ {) R; U% k- {B. DF Bit Clear
+ z* I: p! a& K% I7 `/ ^. lC. IP MTU
( t7 e9 y' b" w- d* KD. PMTUD
- }4 x2 P0 u) {E. http://bbs.hh010.com/
1 t* Z. n3 z; M. d) LF. http://bbs.hh010.com/
5 V( v% i/ I9 ZCorrect Answer: AD
$ W+ {1 {3 {& Z. v" F% X
QUESTION 220
Two GRE sccenarios for preventing(Choose two)
* a0 c  |2 `2 _) kA. TCP MSS
B. DF Bit
C. http://bbs.hh010.com/
1 O- ]6 _9 Q* p% L- P" R, a8 d4 xD. http://bbs.hh010.com/
Correct Answer: AB
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joward

joward

求答案

liugangpaul

QUESTION 202和222问的其实是一样的内容
2 P) u) n- r- M3 Z- K4 ?+ [0 d/ c6 h参考CCNP学习指南英文版（300新版）关于uRPF的叙述：
% X9 b9 w" {+ x3 g7 \Network administrators can use Unicast Reverse Path Forwarding (uRPF) to help limit
$ M* g. P  _" S7 Sthe malicious traffic on an enterprise network. This security feature works with Cisco
Express Forwarding (CEF) by enabling the router to verify that the source of any IP
" O0 \( m* B$ i6 ~  mpackets received is in the CEF table and reachable via the routing table. If the source IP
+ R6 u4 q" h% o) ^, y) `address is not valid, the packet is discarded.
$ N5 P6 R8 b$ X( Y1 g9 t
! c. n' T5 p, i) I6 naccess list与ACL有关，可以排除
CEF和FIB，我倾向于选FIB，符合上述中的reachable via the routing table
6 Q9 {% p3 c' N5 U
- y7 ]; \- m* z, O+ |' M3 `+ m

请各位指教

liugangpaul

220和223看起来也像同一道题，我选TCP MSS和PMTUD
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参见http://www.cisco.com/c/en/us/sup ... 5-pmtud-ipfrag.html

maomaoqd

请教有正确答案了吗?