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Network Security Firewalls
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RE: PIX dhcprelay via IPSec.

Subject: RE: PIX dhcprelay via IPSec.
Date: Fri, 17 Mar 2006 08:58:43 +0100
Hi Cosmin,

Here are the relevant parts (things in caps are sanitized):

REMOTE SITE PIX

hostname REMOTE
access-list outside_access_in permit icmp any interface outside
echo-reply 
access-list outside_access_in permit ip any any 
access-list inside_access_out permit ip any any 
logging on
logging buffered informational
ip address outside REMOTE_OUTSIDE 255.255.255.240
ip address inside REMOTE_INSIDE 255.255.255.0
global (outside) 1 interface
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
access-group outside_access_in in interface outside
access-group inside_access_out in interface inside
route outside 0.0.0.0 0.0.0.0 CORRECT_STANDARD_GW 1
management-access inside
dhcprelay server DHCP_IP outside
dhcprelay enable inside
vpnclient server GATEWAY_OUTSIDE
vpnclient mode network-extension-mode
vpnclient vpngroup GROUP password GROUP_PW
vpnclient username USER password USER_PW
vpnclient enable

CENTRAL PIX

hostname CENTRAL
access-list outside_access_in permit icmp any interface outside
echo-reply 
access-list inside_access_out permit ip any any 
access-list outside_access_in permit ip any any 
access-list inside_outbound_nat0_acl permit ip any REMOTE_INSIDE
255.255.255.0 
access-list outside_cryptomap_dyn_20 permit ip any REMOTE_INSIDE 0
255.255.255.0 
logging on
logging buffered informational
ip address outside GATEWAY_OUTSIDE 255.255.255.240
ip address inside GATEWAY_INSIDE 255.255.255.0
ip local pool REMOTE_POOL 10.180.248.0-10.180.248.255
global (outside) 1 interface
nat (inside) 0 access-list inside_outbound_nat0_acl
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
access-group outside_access_in in interface outside
access-group inside_access_in in interface outside
route outside 0.0.0.0 0.0.0.0 CORRECT_STANDARD_GW 1
sysopt connection permit-ipsec
crypto ipsec transform-set ESP-3DES-MD5 esp-3des esp-md5-hmac 
crypto dynamic-map outside_dyn_map 20 match address
outside_cryptomap_dyn_20
crypto dynamic-map outside_dyn_map 20 set transform-set ESP-3DES-MD5
crypto map outside_map 65535 ipsec-isakmp dynamic outside_dyn_map
crypto map outside_map client authentication LOCAL 
crypto map outside_map interface outside
isakmp enable outside
isakmp policy 20 authentication pre-share
isakmp policy 20 encryption 3des
isakmp policy 20 hash md5
isakmp policy 20 group 2
isakmp policy 20 lifetime 86400
vpngroup GROUP address-pool REMOTE_POOL
vpngroup GROUP dns-server DNS
vpngroup GROUP wins-server WINS
vpngroup GROUP default-domain DOMAIN.TLD
vpngroup GROUP idle-time 1800
vpngroup GROUP password GROUP_PW
username USER password USER_PW priv 3

Before anyone shoots off that there's no nat 0 rule on the remote side,
remember that this rule comes automagically from the vpnclient, and is
correct - I checked.

The any/any access-lists are, of course, just for testing. So they will
obviously be changed as soon as the boat is afloat (these firewalls and
the VLANs inbetween are actually all on my table at the moment being
tested.) I am also aware that I don't need the inside_access_in
access-lists - I just use them as an easy way to watch the hit counts
for packets being passed.

Thanks for any assistance,

Chris

-----Original Message-----
From: Stejerean, Cosmin [mailto:cosmin@cti.depaul.edu] 
Sent: Thursday, March 16, 2006 11:35 PM
To: Meidinger Chris
Subject: RE: PIX dhcprelay via IPSec.

Sounds to me that you have a problem with routing. Can you do a
traceroute from a client to the DHCP server to make sure that 
the packet
follows the correct route. Why would pinging from the remote 
pix to the
DHCP server work over the inside interface? The inside interface
connects you to the client network not the VPN, right? Can 
you post the
entire config file (after sanitizing any confidential information)?

Cosmin

-----Original Message-----
From: Meidinger Chris [mailto:chris.meidinger@badenIT.de] 
Sent: Thursday, March 16, 2006 1:44 AM
To: Stejerean, Cosmin; firewalls@securityfocus.com
Subject: RE: PIX dhcprelay via IPSec.

Hi Cosmin,

I forgot to mention in my original post, that I can hping on 
udp/67 in both directions as well. 

I've also noticed, that on the remote firewall i can't ping 
the DHCP-Server normally, but i can if I specify the inside 
interface. That is, "ping x.x.x.x" doesn't work, but but 
"ping inside x.x.x.x" does work.

Can anyone think of a reason for that? 

I'd appreciate any more ideas, because I've got quite a bit 
of pressure to get this running.

Thanks,

Chris

-----Original Message-----
From: Stejerean, Cosmin [mailto:cosmin@cti.depaul.edu]
Sent: Thursday, March 16, 2006 3:04 AM
To: Meidinger Chris; firewalls@securityfocus.com
Subject: RE: PIX dhcprelay via IPSec.

Do you have rules to allow traffic on UDP 67 on all the PIX 
boxes? The 
fact that you can ping the DHCP server means you can deliver ICMP 
packets but UDP packets on port 67 might be filtered 
along the way. 
Try to send a UDP packet on port 67 to the DHCP server 
using nmap and 
see if your sniffers pick it up. If it gets dropped you 
should see 
where it gets dropped. If this udp packet makes it 
through then you 
probably have some more serious issue with the remote pix. 
Also make 
sure the return packet can make it's way back to the remote pix.

Regards,

Cosmin Stejerean

-----Original Message-----
From: Meidinger Chris [mailto:chris.meidinger@badenIT.de]
Sent: Wednesday, March 15, 2006 5:22 PM
To: firewalls@securityfocus.com
Subject: PIX dhcprelay via IPSec.

Hi List,

I have a question about relaying DHCP over VPN with PIX.

I have the following setup:

Client
 |
 |
 |
Remote Site PIX running in network-extension mode
|V| 
|P| Internet
|N|
Central PIX acting as concentrator
 |
 |  Net 1
 |
Inside Pix providing access control
 |
 |  Net 2
 |
DHCP Server x.x.x.x

The client needs to talk to the DHCP-Server in Net 2. 
It can ping 
the DHCP fine so routing and all is OK, but the relayed 
Unicasts on 
udp/67 seem to die inside the remote PIX. No log 
messages, no debug 
messages (at least in any debug mode I though to try) and 
still no 
packet.

I have the following config:

hostname(config)# show dhcprelay
dhcprelay server x.x.x.x outside
dhcprelay enable inside

I see statistics,

hostname(config)# show dhcprelay stat Packets Relayed
BOOTREQUEST          0
DHCPDISCOVER         48
DHCPREQUEST          0
DHCPDECLINE          0
DHCPRELEASE          0
DHCPINFORM           0

BOOTREPLY            0
DHCPOFFER            0
DHCPACK              0
DHCPNAK              0

but no packet in Net 1 and no packet in Net 2 (got inline 
sniffers 
in both trying to troubleshoot this)

Can anyone point me in the right direction what the problem
might be?

Thanks in advance,

Chris





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