Routing Issue_please need help

Unanswered Question
Jul 31st, 2009
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i am configuring a cisco2611 and in need of help please.the layout as follow:cable modem > cisco851 (service provider router-i believe in bridge mode) > cisco2611.

i am not able to:

1-get internet connection.

2-not able to get dhcp address on vista laptop. was working and stopped.

router config, extended ping and tracert attached.

thank you for all your help



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Laurent Aubert Fri, 07/31/2009 - 07:07
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  • Cisco Employee,

Hi,


If you can't have a DHCP address, you will not be able to reach the Internet so this is the first issue to fix.


You can run deb ip dhcp server events and deb ip dhcp server packets to see what's going on.


Then you need to translate your traffic so all your traffic will use your true public WAN IP address as the source address:


ip nat inside source list 101 interface Ethernet0/1 overload

!

access-list 101 permit ip 172.20.1.0 0.0.0.255 any

!


also access-list 1 is useless in your config


HTH


Laurent.

mhasabal Fri, 07/31/2009 - 07:41
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Laurent,

thank you so much. you solved my problem.

can you please help me understand why my access list 1 usless and why 101 worked.

thanks again.

Laurent Aubert Fri, 07/31/2009 - 08:44
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  • Cisco Employee,

Hi,


I'm glad to read that !!!


Applying an ACL on an interface which permit anything is like not applying the ACL at all.


ACL 101 filters which packets should be natted and as a best practice I prefer specifying the source subnet.

You can notice ACL 101 is not apply to any interface but to the NAT rule statement.


Don't hesitate to rate my post if it was helpful ;-)


Thanks


Laurent.



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