Here is my setup it work fine.
Building configuration...
Current configuration : 2051 bytes
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version 12.2
service tcp-keepalives-in
service tcp-keepalives-out
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
service udp-small-servers
service tcp-small-servers
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hostname TERM_SRV
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enable password xxxx
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ip subnet-zero
no ip domain-lookup
ip host R4 2004 2.2.2.2
ip host R3 2003 2.2.2.2
ip host R2 2002 2.2.2.2
ip host R1 2001 2.2.2.2
ip host sw2 2008 2.2.2.2
ip host sw3 2009 2.2.2.2
ip host sw1 2011 2.2.2.2
ip host bb1 2012 2.2.2.2
ip host bb2 2013 2.2.2.2
ip host bb3 2014 2.2.2.2
ip host R5 2005 2.2.2.2
ip host R6 2006 2.2.2.2
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chat-script cisco-default ABORT ERROR "" "AT Z" OK "ATDT \T" TIMEOUT 30 \c CONNECT
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!
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interface Loopback0
ip address 2.2.2.2 255.255.255.255
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interface Ethernet0
ip address x.x.x.x 255.255.255.0
no ip route-cache
no ip mroute-cache
!
interface Serial0
no ip address
no ip route-cache
no ip mroute-cache
shutdown
!
interface Serial1
no ip address
no ip route-cache
no ip mroute-cache
shutdown
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no ip http server
ip classless
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alias exec r1 telnet r1 2001
alias exec r2 telnet r2 2002
alias exec r3 telnet r3 2003
alias exec r4 telnet r4 2004
alias exec r5 telnet r5 2005
alias exec r6 telnet r6 2006
alias exec sw1 telnet sw1 2007
alias exec sw2 telnet sw1 2008
alias exec sw3 telnet sw1 2009
alias exec sw4 telnet sw1 2010
alias exec bb1 telnet bb1 2011
alias exec bb2 telnet bb2 2012
alias exec bb3 telnet bb3 2013
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line con 0
exec-timeout 0 0
logging synchronous
telnet speed 9600 9600
line 1 16
no exec
transport input telnet
telnet speed 9600 9600
autohangup
stopbits 1
Not sure why you have the NAT configuration.
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