topic IPSec L2L and NAT in Network Security

IPSec L2L and NAT

Statically — Tue, 12 Mar 2019 00:06:04 GMT

Good afternoon,

Sorry for asking such a beginner question but I am running a little short on time so thought I would post in here as you are always so very helpful while researching myself.

I have two ASAs set up in a lab which I have set up a Site-to-Site VPN and all is well. I also need to add PAT to the devices so any traffic not destined for the VPN go out to the default route on the ASA. The problem is whenever I add the typical PAT command of

Nat (inside,outside) source dynamic NAT interface (with NAT being a network object of my subnet)

or similar, this instantly stops any traffic flowing down the VPN. Excuse my novice-ness, any help would be greatly appreciated as I am sure I am not using my brain here!

Kind regards,

Sam

IPSec L2L and NAT

Statically — Mon, 08 Oct 2012 15:30:03 GMT

Apologies these are two 5505s and using 8.4.

IPSec L2L and NAT

Statically — Mon, 08 Oct 2012 15:48:51 GMT

Also - running config, as you can see I used ASDM for the VPN, just for speed purposes -

ASA Version 8.4(4)1
!
hostname ciscoasa
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
names
!
interface Ethernet0/0
!
interface Ethernet0/1
switchport access vlan 2
!
interface Ethernet0/2
shutdown
!
interface Ethernet0/3
shutdown
!
interface Ethernet0/4
shutdown
!
interface Ethernet0/5
shutdown
!
interface Ethernet0/6
shutdown
!
interface Ethernet0/7
shutdown
!
interface Vlan1
nameif outside
security-level 0
ip address 192.168.0.2 255.255.255.0
!
interface Vlan2
nameif inside
security-level 100
ip address 10.240.0.1 255.255.255.0
!
ftp mode passive
object network NAT
subnet 10.240.0.0 255.255.255.0
access-list outside_cryptomap extended permit ip 10.240.0.0 255.255.255.0 10.240 .1.0 255.255.255.0
access-list from_outside extended permit icmp any any echo
pager lines 24
logging enable
logging asdm informational
mtu outside 1500
mtu inside 1500
icmp unreachable rate-limit 1 burst-size 1
no asdm history enable
arp timeout 14400
route outside 0.0.0.0 0.0.0.0 192.168.0.1 1
timeout xlate 3:00:00
timeout pat-xlate 0:00:30
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00
timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00
timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute
timeout tcp-proxy-reassembly 0:01:00
timeout floating-conn 0:00:00
dynamic-access-policy-record DfltAccessPolicy
user-identity default-domain LOCAL
http server enable
http 10.240.0.0 255.255.255.0 inside
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart warmstart
crypto ipsec ikev1 transform-set ESP-AES-128-SHA esp-aes esp-sha-hmac
crypto ipsec ikev1 transform-set ESP-AES-128-MD5 esp-aes esp-md5-hmac
crypto ipsec ikev1 transform-set ESP-AES-192-SHA esp-aes-192 esp-sha-hmac
crypto ipsec ikev1 transform-set ESP-AES-192-MD5 esp-aes-192 esp-md5-hmac
crypto ipsec ikev1 transform-set ESP-AES-256-SHA esp-aes-256 esp-sha-hmac
crypto ipsec ikev1 transform-set ESP-AES-256-MD5 esp-aes-256 esp-md5-hmac
crypto ipsec ikev1 transform-set ESP-3DES-SHA esp-3des esp-sha-hmac
crypto ipsec ikev1 transform-set ESP-3DES-MD5 esp-3des esp-md5-hmac
crypto ipsec ikev1 transform-set ESP-DES-SHA esp-des esp-sha-hmac
crypto ipsec ikev1 transform-set ESP-DES-MD5 esp-des esp-md5-hmac
crypto ipsec ikev2 ipsec-proposal DES
protocol esp encryption des
protocol esp integrity sha-1 md5
crypto ipsec ikev2 ipsec-proposal 3DES
protocol esp encryption 3des
protocol esp integrity sha-1 md5
crypto ipsec ikev2 ipsec-proposal AES
protocol esp encryption aes
protocol esp integrity sha-1 md5
crypto ipsec ikev2 ipsec-proposal AES192
protocol esp encryption aes-192
protocol esp integrity sha-1 md5
crypto ipsec ikev2 ipsec-proposal AES256
protocol esp encryption aes-256
protocol esp integrity sha-1 md5
crypto map outside_map 1 match address outside_cryptomap
crypto map outside_map 1 set pfs
crypto map outside_map 1 set peer 192.168.1.2
crypto map outside_map 1 set ikev1 transform-set ESP-AES-128-SHA ESP-AES-128-MD5 ESP-AES-192-SHA ESP-AES-192-MD5 ESP-AES-256-SHA ESP-AES-256-MD5 ESP-3DES-SHA ES P-3DES-MD5 ESP-DES-SHA ESP-DES-MD5
crypto map outside_map 1 set ikev2 ipsec-proposal AES256 AES192 AES 3DES DES
crypto map outside_map 1 set nat-t-disable
crypto map outside_map interface outside
crypto ikev2 policy 1
encryption aes-256
integrity sha
group 5 2
prf sha
lifetime seconds 86400
crypto ikev2 policy 10
encryption aes-192
integrity sha
group 5 2
prf sha
lifetime seconds 86400
crypto ikev2 policy 20
encryption aes
integrity sha
group 5 2
prf sha
lifetime seconds 86400
crypto ikev2 policy 30
encryption 3des
integrity sha
group 5 2
prf sha
lifetime seconds 86400
crypto ikev2 policy 40
encryption des
integrity sha
group 5 2
prf sha
lifetime seconds 86400
crypto ikev2 enable outside
crypto ikev1 enable outside
crypto ikev1 policy 10
authentication crack
encryption aes-256
hash sha
group 2
lifetime 86400
crypto ikev1 policy 20
authentication rsa-sig
encryption aes-256
hash sha
group 2
lifetime 86400
crypto ikev1 policy 30
authentication pre-share
encryption aes-256
hash sha
group 2
lifetime 86400
crypto ikev1 policy 40
authentication crack
encryption aes-192
hash sha
group 2
lifetime 86400
crypto ikev1 policy 50
authentication rsa-sig
encryption aes-192
hash sha
group 2
lifetime 86400
crypto ikev1 policy 60
authentication pre-share
encryption aes-192
hash sha
group 2
lifetime 86400
crypto ikev1 policy 70
authentication crack
encryption aes
hash sha
group 2
lifetime 86400
crypto ikev1 policy 80
authentication rsa-sig
encryption aes
hash sha
group 2
lifetime 86400
crypto ikev1 policy 90
authentication pre-share
encryption aes
hash sha
group 2
lifetime 86400
crypto ikev1 policy 100
authentication crack
encryption 3des
hash sha
group 2
lifetime 86400
crypto ikev1 policy 110
authentication rsa-sig
encryption 3des
hash sha
group 2
lifetime 86400
crypto ikev1 policy 120
authentication pre-share
encryption 3des
hash sha
group 2
lifetime 86400
crypto ikev1 policy 130
authentication crack
encryption des
hash sha
group 2
lifetime 86400
crypto ikev1 policy 140
authentication rsa-sig
encryption des
hash sha
group 2
lifetime 86400
crypto ikev1 policy 150
authentication pre-share
encryption des
hash sha
group 2
lifetime 86400
crypto ikev1 policy 65535
authentication pre-share
encryption 3des
hash sha
group 2
lifetime 86400
telnet timeout 5
ssh timeout 5
ssh key-exchange group dh-group1-sha1
console timeout 0

threat-detection basic-threat
threat-detection statistics access-list
no threat-detection statistics tcp-intercept
webvpn
group-policy GroupPolicy_192.168.1.2 internal
group-policy GroupPolicy_192.168.1.2 attributes
vpn-tunnel-protocol ikev1 ikev2
username planetadmin password HQcYarQj.Yoy8WE9 encrypted privilege 15
tunnel-group 192.168.1.2 type ipsec-l2l
tunnel-group 192.168.1.2 general-attributes
default-group-policy GroupPolicy_192.168.1.2
tunnel-group 192.168.1.2 ipsec-attributes
ikev1 pre-shared-key *****
ikev2 remote-authentication pre-shared-key *****
ikev2 local-authentication pre-shared-key *****
!
class-map inspection_default
match default-inspection-traffic
!
!
policy-map type inspect dns preset_dns_map
parameters
message-length maximum client auto
message-length maximum 512
policy-map global_policy
class inspection_default
inspect dns preset_dns_map
inspect ftp
inspect h323 h225
inspect h323 ras
inspect ip-options
inspect netbios
inspect rsh
inspect rtsp
inspect skinny
inspect esmtp
inspect sqlnet
inspect sunrpc
inspect tftp
inspect sip
inspect xdmcp
inspect icmp
!
service-policy global_policy global
prompt hostname context
no call-home reporting anonymous
call-home
profile CiscoTAC-1
no active
destination address http https://tools.cisco.com/its/service/oddce/services/DD CEService
destination address email callhome@cisco.com
destination transport-method http
subscribe-to-alert-group diagnostic
subscribe-to-alert-group environment
subscribe-to-alert-group inventory periodic monthly
subscribe-to-alert-group configuration periodic monthly
subscribe-to-alert-group telemetry periodic daily
Cryptochecksum:86b9d6214f504d9ca205b610613c4a78
: end

IPSec L2L and NAT

Julio Carvajal — Mon, 08 Oct 2012 18:35:04 GMT

Hello Sam,

Where is the NAT setup??

Anyway, here is what you need

object network local_lan

subnet 10.240.0.0 255.255.255.0

object network remote-lan

subnet 10.240.1.0 255.255.255.0

nat (inside,outside) source static local_lan local_lan destination static remote-lan remote-lan

nat (inside,outside) source dynamic any interface

Any other question..Sure..Just remember to rate all of my helpful answers

Julio

IPSec L2L and NAT

Statically — Mon, 08 Oct 2012 19:25:34 GMT

Hello Julio,

Sorry, I had removed the NAT at the time for testing puposes. I think you may be my new hero. Unfortunately I'm not going to be able to test it for the time being but I think you are certainly on the right lines. I had not set a specific nat entry for the VPN so it was being sent through the dynamic NAT. Excuse when I kept mentioning PAT, I had been doing port redirection all afternoon....

The thing that throws me is, I would not have thought an L2L VPN would need NAT if the networks were connecting to each other, so am a touch confused....

nat (inside,outside) source static local_lan local_lan destination static remote-lan remote-lan

What does the previous command actually do?

Many thanks for your help.

Sam

IPSec L2L and NAT

Julio Carvajal — Mon, 08 Oct 2012 19:27:24 GMT

Hello,

That NAT rule will not NAT the traffic when the source is X ( Local_lan) and Y is the destination ( Destination_Lan)

So basically we are letting the ASA know, Do not NAT the VPN traffic

Any other question..Sure..Just remember to rate all of my helpful answers

IPSec L2L and NAT

Statically — Mon, 08 Oct 2012 19:59:07 GMT

You are beyond a legend, and no I will not forget, I'm not the type to not appreciate advice.

Thanks once again.

Sam

IPSec L2L and NAT

Julio Carvajal — Mon, 08 Oct 2012 20:43:31 GMT

Hello Sam,

Thanks for all your kind words.

have a great day

Julio