Lock and Key

From: GAURAV MADAN (gauravmadan1177@gmail.com)
Date: Sat Aug 30 2008 - 10:16:52 ART


Hi Friends

Dynamic ACL is something that troubles me all the time whenever i get
the question on same .
PLease help me understanding the concept .

I labbed the following scenario

R4
   \
    \
     \
      R1
      /
     /
    /
 R5

I want if from R4 ; I telnet to 150.1.1.1 (R1 loopback ) on line 3023
; it should land me in R1
However if I do simple telnet 150.1.1.1 ; it should land me on R5
I am using login local ( username CISCO password CISCO )

R1
*****
Rack1R1(config)#do sh ip access-li
Extended IP access list 101
    10 permit tcp any any eq telnet
    20 permit tcp any any eq 3023 (8 matches)

Extended IP access list TELNET
    10 Dynamic 10 permit tcp any any eq telnet
       permit tcp any any eq telnet (26 matches) (time left 287)
    20 deny tcp any host 150.1.5.5 eq telnet
    30 permit ip any any (68 matches)

line vty 0 1
 password cisco
 login local
 autocommand access-enable timeout 5
line vty 2 4
 access-class 101 in
 password cisco
 login local
 rotary 23
!
int s0/1/0.1
ip access-group TELNET in
!
================ 1st requirement works fine =================
Rack1R4#telnet 150.1.1.1 3023
Trying 150.1.1.1, 3023 ... Open

User Access Verification

Username: CISCO
Password:
Rack1R1>
================= 2nd requirement dont work ==================

Rack1R4#telnet 150.1.1.1
Trying 150.1.1.1 ... Open

User Access Verification

Username: CISCO
Password:
[Connection to 150.1.1.1 closed by foreign host]
Rack1R4#telnet 150.1.1.1
Trying 150.1.1.1 ... Open

User Access Verification

Username: CISCO
Password:
% List#TELNET-10 already contains this IP address pair
[Connection to 150.1.1.1 closed by foreign host]
Rack1R4#

================================================

Please guide me in this context

Thnx
Gaurav Madan.

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