RE: S2S VPN: why are static routes sometimes needed?
- From: "Stefaan Pouseele" <stefaan.pouseele@xxxxxxxxx>
- To: "'[ISAserver.org Discussion List]'" <isalist@xxxxxxxxxxxxx>
- Date: Wed, 28 Dec 2005 13:10:27 +0100
Hi Jim,
OK, I took up the challenge and replaced ISA-B with a Windows 2003 RRAS
server :-)
With the help of
http://support.microsoft.com/default.aspx?scid=kb;en-us;816514 I configured
an IPSec tunnel to the ISA-A. Guess what... you are right! I found exact the
same behavior.
I even simplified further the test environment as follows:
192.168.1.0/24
vvv
LAN-A -------- [ISA-A] ---+
192.168.22.0/24 .10 !
+--- [RTR] --- Internet
! .1
.30 !
LAN-B -------- [ISA-B] ---+
192.168.44.0/24
On ISA-A:
---------
Remote Site Network contains:
- 192.168.1.30/32
- 192.168.44.0/24
If Default gateway = 192.168.1.1 then the static route '192.168.44.0/24
Gateway 192.168.1.30' is needed.
If Default gateway = 192.168.1.30 then no static routes are needed.
On ISA-B:
---------
Remote Site Network contains:
- 192.168.1.10/32
- 192.168.22.0/24
If Default gateway = 192.168.1.1 then the static route '192.168.22.0/24
Gateway 192.168.1.10' is needed.
If Default gateway = 192.168.1.10 then no static routes are needed.
Thanks,
Stefaan
-----Original Message-----
From: Jim Harrison [mailto:Jim@xxxxxxxxxxxx]
Sent: dinsdag 27 december 2005 21:23
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: S2S VPN: why are static routes sometimes needed?
http://www.ISAserver.org
That is odd, but I'll bet you find that this behavior is the same without
ISA.
RRAS and the TCP/IP stack, not ISA, handle the actual packet routing.
--------------------------------------------
Jim Harrison
MCP(NT4, W2K), A+, Network+, PCG
http://isaserver.org/Jim_Harrison/
http://isatools.org
Read the help / books / articles!
--------------------------------------------
-----Original Message-----
From: Stefaan Pouseele [mailto:stefaan.pouseele@xxxxxxxxx]
Sent: Tuesday, December 27, 2005 4:58 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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