ну тогда попробуй следующее - поставь маскарад на это подключение и будет тебе щасте.
например запретил входящие пинги и еще чего.
зы: и какой ТТЛ у пинга с роутера показывает?
и ещё - с TTL в mangle нет никаких приколов? проверь все закладки файрвола
[admin@MikroTik] > /ip firewall mangle print
Flags: X - disabled, I - invalid, D - dynamic
0 D ;;; special dummy rule to show fasttrack counters
chain=prerouting action=passthrough
1 D ;;; special dummy rule to show fasttrack counters
chain=forward action=passthrough
2 D ;;; special dummy rule to show fasttrack counters
chain=postrouting action=passthrough
[admin@MikroTik] > /ip route print
Flags: X - disabled, A - active, D - dynamic,
C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme,
B - blackhole, U - unreachable, P - prohibit
# DST-ADDRESS PREF-SRC GATEWAY DISTANCE
0 ADS 0.0.0.0/0 192.168.0.1 1
1 ADC 192.168.0.0/24 192.168.0.3 ether1 0
2 ADC 192.168.112.254/32 192.168.112.40 <ИМЯ> 0
3 X S 192.168.113.0/24 <ИМЯ> 1
4 ADC 192.168.141.0/24 192.168.141.1 bridge 0
[admin@MikroTik] /ip firewall filter> /ip route print
Flags: X - disabled, A - active, D - dynamic,
C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme,
B - blackhole, U - unreachable, P - prohibit
# DST-ADDRESS PREF-SRC GATEWAY DISTANCE
0 ADS 0.0.0.0/0 192.168.0.1 1
1 ADC 192.168.0.0/24 192.168.0.3 ether1 0
2 ADC 192.168.XXX.254/32 192.168.XXX.YYY <ИМЯ> 0
3 A S 192.168.ZZZ.0/24 <ИМЯ> 1
4 ADC 192.168.CCC.0/24 192.168.DDD.1 bridge
либо на самом компе
[admin@MikroTik] /ip firewall filter> print
Flags: X - disabled, I - invalid, D - dynamic
0 D ;;; special dummy rule to show fasttrack counters
chain=forward action=passthrough
1 ;;; defconf: accept established,related,untracked
chain=input action=accept connection-state=established,related,untracked
log=no log-prefix=""
2 ;;; defconf: drop invalid
chain=input action=drop connection-state=invalid log=no log-prefix=""
3 ;;; defconf: accept ICMP
chain=input action=accept protocol=icmp log=no log-prefix=""
4 ;;; defconf: drop all not coming from LAN
chain=input action=drop in-interface-list=!LAN log=no log-prefix=""
5 ;;; defconf: accept in ipsec policy
chain=forward action=accept log=no log-prefix="" ipsec-policy=in,ipsec
6 ;;; defconf: accept out ipsec policy
chain=forward action=accept log=no log-prefix="" ipsec-policy=out,ipsec
7 ;;; defconf: fasttrack
chain=forward action=fasttrack-connection
connection-state=established,related log=no log-prefix=""
8 ;;; defconf: accept established,related, untracked
chain=forward action=accept
connection-state=established,related,untracked log=no log-prefix=""
9 ;;; defconf: drop invalid
chain=forward action=drop connection-state=invalid log=no log-prefix=""
10 ;;; defconf: drop all from WAN not DSTNATed
chain=forward action=drop connection-state=new
connection-nat-state=!dstnat in-interface-list=WAN log=no log-prefix="
[admin@MikroTik] /ip firewall filter> /interface print
Flags: D - dynamic, X - disabled, R - running, S - slave
# NAME TYPE ACTUAL-MTU L2MTU MAX-L2MTU
0 R ether1 ether 1500 1598 9214
1 RS ether2 ether 1500 1598 9214
2 S ether3 ether 1500 1598 9214
3 S ether4 ether 1500 1598 9214
4 S ether5 ether 1500 1598 9214
5 XS wlan2Ghz wlan 1500 1600 2290
6 RS wlan5Ghz wlan 1500 1600 2290
7 R <ИМЯ> l2tp-out 1450
8 R ;;; defconf
bridge bridge 1500 159
[admin@MikroTik] /ip firewall filter> /ip route print
Flags: X - disabled, A - active, D - dynamic,
C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme,
B - blackhole, U - unreachable, P - prohibit
# DST-ADDRESS PREF-SRC GATEWAY DISTANCE
0 ADS 0.0.0.0/0 192.168.0.1 1
1 ADC 192.168.0.0/24 192.168.0.3 ether1 0
2 ADC 192.168.XXX.254/32 192.168.XXX.YYY <ИМЯ> 0
3 A S 192.168.ZZZ.0/24 <ИМЯ> 1
4 ADC 192.168.CCC.0/24 192.168.DDD.1 bridge
P.S. В Cisco Packet Tracer'е в университете на парах было не так весело ковыряться как здесь =)