Kingsley,

 

icmp error will not allow traceroute back in.  Instead what it is used for
is when you are using NAT on the inside.  It translates the source address
in a packet to allow the icmp error return traffic to be directed to the
correct source.  It hides the internal address from the external networks
but still requires you to allow time-exceeded and unreachable on the outside
ACL.  Without the command the ASA hides the source address.

 

http://www.cisco.com/en/US/docs/security/asa/asa82/command/reference/i2.html
#wp1736134

 

 

 

Regards,

 

Tyson Scott - CCIE #13513 R&S and Security

Technical Instructor - IPexpert, Inc.


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From: [email protected]
[mailto:[email protected]] On Behalf Of Kingsley
Charles
Sent: Tuesday, September 29, 2009 10:49 AM
To: [email protected]
Subject: Re: [OSL | CCIE_Security] Traceroute across ASA

 

typo 

 

first solution is 

 

Solution 1

 

Allowing the "time-exceeded" and "unreachable" to outside interface.

 

access-list mine extended permit icmp any any time-exceeded
access-list mine extended permit icmp any any unreachable

 

access-group icmpany in interface outside



 

On Tue, Sep 29, 2009 at 7:52 PM, Kingsley Charles
<[email protected]> wrote:

Hi all

 

I am trying two solutions for getting "traceroute" across ASA to work. First
solution is working for me but the second solution is not working.

Am I missing something?

 

 

Solution 1

 

Allowing the "time-exceeded" and "unreachable" to outside interface.

 

access-list mine extended permit icmpacl any any time-exceeded
access-list mine extended permit icmpacl any any unreachable

 

access-group icmpany in interface outside

 

 

Solution 2

 

I am not allowing the "time-exceeded" and "unreachable" to outside
interface. Rather I am relying on inspect icmp and icmp error.

 

policy-map global_policy
 class inspection_default
  inspect dns migrated_dns_map_1
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect netbios
  inspect rsh
  inspect rtsp
  inspect skinny
  inspect esmtp
  inspect sqlnet
  inspect sunrpc
  inspect tftp
  inspect sip
  inspect xdmcp
  inspect icmp
  inspect icmp error

 

 

With regards

Kings

 

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