RE: S2S VPN: why are static routes sometimes needed?
- From: "Thomas W Shinder" <tshinder@xxxxxxxxxxx>
- To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
- Date: Tue, 27 Dec 2005 07:32:59 -0600
Hi Stefaan,
I don't know all the details, but I do know that routing support for
IPSec tunnel mode in problematic, and one of the reasons why its not
recommended, especially if you're connecting two ISA firewalls. If ISA
firewalls are on each side, you should be using L2TP/IPSec to get better
routing support.
HTH,
Tom
Thomas W Shinder, M.D.
Site: www.isaserver.org
Blog: http://spaces.msn.com/members/drisa/
Book: http://tinyurl.com/3xqb7
MVP -- ISA Firewalls
**Who is John Galt?**
> -----Original Message-----
> From: Stefaan Pouseele [mailto:stefaan.pouseele@xxxxxxxxx]
> Sent: Tuesday, December 27, 2005 6:58 AM
> To: [ISAserver.org Discussion List]
> Subject: [isalist] S2S VPN: why are static routes sometimes needed?
>
> http://www.ISAserver.org
>
> Hi,
>
> it seems that if a S2S VPN connection of type IPSec Tunnel is
> used and if
> the remote tunnel endpoint can't be reached through the
> default gateway,
> then you need to create extra static routes for the remote
> network ID's
> reachable through that remote tunnel endpoint. I don't
> understand why this
> is needed? Take note that there were no problems in setting
> up the IPSec MM
> and QM SA's!
>
> To explain it better, here is a little diagram of the lab setup:
>
> 192.168.1.0/24
> vvv
> LAN-A -------- [ISA-A] ---+
> 192.168.22.0/24 .10 !
> +--- [RTR] --- Internet
> ! .1
> .30 !
> [RTR-B]
> ! .1
> .10 !
> LAN-B -------- [ISA-B] ---+
> 192.168.44.0/24 ^^^
> 192.168.11.0/24
>
>
> On ISA-A:
> ---------
>
> Remote Site Network contains:
> - 192.168.11.10/32
> - 192.168.44.0/24
>
> Default gateway: 192.168.1.1
>
> Static routes configured:
> - 192.168.11.0/24 Gateway 192.168.1.30
> - 192.168.44.0/24 Gateway 192.168.1.30 <<<< WHY is this one needed ???
>
>
> On ISA-B:
> ---------
>
> Remote Site Network contains:
> - 192.168.1.10/32
> - 192.168.22.0/24
>
> Default Gateway: 192.168.11.1
>
> No static routes configured.
>
>
> Test:
> -----
>
> From a host on LAN-B ping a host on LAN-A. Without the static route
> '192.168.44.0/24 Gateway 192.168.1.30' on ISA-A, I can see
> the ping request
> and reply on LAN-A but the reply never makes it back to
> LAN-B. The ping
> reply just disappeared into thin air! Creating the static
> route and bingo,
> it works. What's the logic behind this behavior?
>
>
> Thanks,
> Stefaan
>
>
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