Re: Cisco PIX - "Allow inbound IPsec sessions to bypass interface access lists"

[Paul Melson <pmelson () gmail com>]

On Wed, May 13, 2009 at 7:31 AM, Michael Tewner <tewner () gmail com> wrote:
> As I understand it, by default, incoming packets from IPsec site-to-site
> VPN's are not checked by the standard interface ACL's -
>
> (1) Where _can_ I limit incoming traffic from a specific VPN - i.e. SSH from
> a specific remote host to a local host/LAN?

I don't believe this is default behavior, and it's certainly easy
enough to configure.  You can use the interface-bound access lists to
control VPN traffic.

> (2) I found that following checkbox in the "IPsec VPN Wizard" which might be
> a step in the right direction - "Enable inbound IPsec sessions to bypass
> interface access lists."
>      (a) Is this the proper setting?

Yes, this is just the ASDM/PDM checkbox for the 'sysopt connection
permit-ipsec' command.  If you unset that option in your config, IPSec
traffic will be subject to the same access lists that unencrypted
traffic is.

>      (b) I assume that this will send the incoming traffic through the
> "outside" interface? right?

Yes, the access-group that is configured for "in interface outside"
will affect traffic being decrypted by your firewall.  Similarly, the
access-group configured for "in interface inside" (if you do egress
filtering) will affect traffic being encrypted.

>      (c) Does this checkbox apply to ALL IPsec sessions on all VPN's? Will
> this apply to my other VPN's?

Yes, all of your IPSec tunnels, anyway.  I don't know for certain, but
I think SSL VPN connections are unaffected by this setting.

>      (d) What Cisco ASA/PIX command does this translate to

sysopt connection permit-ipsec

>      (e) Is there a screen in the ASDM where I can enable this
> after-the-fact?

No idea.  I've never been a fan of ASDM/PDM.


> (3) Or, perhaps, I'm looking in completely the wrong place?

I'd say you're right on track.

PaulM
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