Tag Archives: phase 2

Cisco ASA: Received a DELETE PFKey message from IKE

Posted on by
Reply

KB ID 0001720

Problem

I was debugging a VPN tunnel today. (From a Fortigate to a Cisco ASAv). I was messing around with the encryption and hashing, when the tunnel fell over. Phase 1 was establishing fine but not Phase 2 (IPSEC). 

I’ve got better skills on the ASA, so that’s where I was debugging;

[box]

IPSEC: Received a PFKey message from IKE
IPSEC: Parsing PFKey GETSPI message
IPSEC: Creating IPsec SA
IPSEC: Getting the inbound SPI
IPSEC DEBUG: Inbound SA (SPI 0x00000000) state change from inactive to embryonic
IPSEC: New embryonic SA created @ 0x00007fc98613ea60,
    SCB: 0x85567700,
    Direction: inbound
    SPI      : 0x3B5A332E
    Session ID: 0x00004000
    VPIF num  : 0x00000002
    Tunnel type: l2l
    Protocol   : esp
    Lifetime   : 240 seconds
IPSEC: Received a PFKey message from IKE
IPSEC DEBUG: Received a DELETE PFKey message from IKE for an inbound SA (SPI 0x3B5A332E)
IPSEC DEBUG: Inbound SA (SPI 0x3B5A332E) destroy started, state embryonic
IPSEC: Destroy current inbound SPI: 0x3B5A332E
IPSEC DEBUG: Inbound SA (SPI 0x3B5A332E) free started, state embryonic
IPSEC DEBUG: Inbound SA (SPI 0x3B5A332E) state change from embryonic to dead
IPSEC DEBUG: Inbound SA (SPI 0x3B5A332E) free completed
IPSEC DEBUG: Inbound SA (SPI 0x3B5A332E) destroy completed

[/box]

Solution

Google that error and you get some posts about NAT, that we’re  not applicable to me. I took a look on the Fortigate and the only clue there was;

[box]

Forti-FW # diagnose vpn tunnel list
list all ipsec tunnel in vd 0
------------------------------------------------------
name=Tunnel-To-SiteB ver=2 serial=1 192.168.100.100:0->192.168.100.111:0 dst_mtu=1500
bound_if=4 lgwy=static/1 tun=intf/0 mode=auto/1 encap=none/512 options[0200]=frag-rfc  run_state=0 accept_traffic=0 overlay_id=0

proxyid_num=1 child_num=0 refcnt=14 ilast=1 olast=782 ad=/0
stat: rxp=0 txp=0 rxb=0 txb=0
dpd: mode=on-demand on=1 idle=20000ms retry=3 count=0 seqno=0
natt: mode=none draft=0 interval=0 remote_port=0
proxyid=Tunnel-To-SiteB proto=0 sa=0 ref=1 serial=2
  src: 0:192.168.1.0/255.255.255.0:0
  dst: 0:172.16.1.0/255.255.255.0:0
run_tally=1

[/box]

There’s not much I can discern from that either; 

sa=0 There is a mismatch between selectors (or no traffic is being initiated).
sa=1 IPsec SA is matching and there is traffic between the selectors.
sa=2 Only seen during IPsec SA rekey

So I went back to basics and checked the Phase 2 on BOTH, firstly the Fortigate;

For the uninitiated: GCM Protocols DON’T require a hashing algorithm, (that’s why you can’t see SHA or MD5 on there), they disappear when a GCM protocol is selected.

Then on the Cisco ASA;

[box]

Cisco-ASA(config-ipsec-proposal)# show run crypto ipsec
crypto ipsec ikev2 ipsec-proposal FORTIGATE
 protocol esp encryption aes-gmac-256
 protocol esp integrity null <--Note: This can say anything it gets ignored!

[/box]

Or if you prefer the ASDM;

THE ANSWER IS STARING YOU/ME IN THE FACE. I just didn’t realise yet, I changed the phase 2 protocols to DES/MD5 and the tunnel came up, I walked up through the protocols and options and discovered what I’d done wrong.

Root Cause: The ASA is set to use AES-GMAC-256 that’s a DIFFERENT PROTOCOL to the AES256GCM configured on the Fortigate! The ASA should be set to AES-GCM-256! (So the Phase 2 proposals didn’t match).

[box]

Cisco-ASA(config)# crypto ipsec ikev2 ipsec-proposal FORTIGATE
Cisco-ASA(config-ipsec-proposal)# protocol esp encryption aes-gcm-256
WARNING: GCM\GMAC are authenticated encryption algorithms.esp integrity config is ignored

[/box]

Or, via ASDM (from the same location as above);

Problem solved!

Related Articles, References, Credits, or External Links

NA

Cisco PIX 500 – IPSEC Site to Site VPNs (v6)

Posted on by

KB ID 0000611 

Problem

Note: This is for firewalls running an operating system BEFORE version 7, if you have an PIX running version 7 or above go here instead. I’ll run though he commands first and then the configuration from PDM at the end.

Solution

PIX 500: Configure a site to site VPN from command line

1. Connect to the PIX, go to “enable mode”, then to “Configure terminal mode”

[box]

User Access Verification

Password:
Type help or '?' for a list of available commands.
PetesPIX> enable
Password: ********
PetesPIX# configure Terminal
PetesPIX(config)#

[/box]

2. I’m assuming the network BEHIND the PIX 500 is 192.168.124.0/24 and the network at the far end of the tunnel is 192.168.123.0/24. So I’m going to create two ACL’s one to tell the PIX that this traffic should be encrypted, and the second to tell the PIX NOT to perform NAT on the VPN traffic.

Note: Yes I can use one ACL, but having two makes it easier to troubleshoot any VPN problems.

[box]

PetesPIX(config)# access-list VPN_CRYPTO_ACL permit ip 192.168.124.0 255.255.255.0 192.168.123.0 255.255.255.0
PetesPIX(config)# access-list VPN_NO_NAT line 1 permit ip 192.168.124.0 255.255.255.0 192.168.123.0 255.255.255.0

[/box]

3. Now I’ve got an ACL that will stop performing NAT I need to add it as a “Nat 0” (this means don’t perform NAT).

Note: Check to make sure you do not already have a nat(inside) 0 xxx command, if you do, use the SAME ACL that is already in use.

[box]

PetesPIX(config)# nat (inside) 0 access-list VPN_NO_NAT

[/box]

4. To set up all the VPN parameters you need to create a crypto map. In the example below I set the peer IP (the firewall at the other end of the tunnel), to 81.81.81.81. Then I tie it to the ACL I created earlier (VPN_CRYPTO_ACL). I’ve set the encryption and hashing used for the tunnel to 3DES and SHA (These will be used for IPSec (Phase 2)). Set the timeouts for the tunnel, and finally apply the cryptomap I’ve just created, to the outside interface.

[box]

PetesPIX(config)# crypto map VPN_CRYPTO_MAP 20 set peer 81.81.81.81
PetesPIX(config)# crypto map VPN_CRYPTO_MAP 20 match address VPN_CRYPTO_ACL
PetesPIX(config)# crypto ipsec transform-set ESP-3DES-SHA esp-3des esp-sha-hmac
PetesPIX(config)# crypto map VPN_CRYPTO_MAP 20 set transform-set ESP-3DES-SHA
PetesPIX(config)# crypto map VPN_CRYPTO_MAP 20 set security-association lifetime seconds 28800 kilobytes 4608000
PetesPIX(config)# crypto map VPN_CRYPTO_MAP interface outside

[/box]

5. The next command lets VPN traffic bypass any other ACLs configured on the firewall.

[box]

PetesPIX(config)# sysopt connection permit-ipsec

[/box]

6. I’m using a “shared secret” that also needs to be setup on the other end of the tunnel. As I said earlier the peer IP is 81.81.81.81.

[box]

PetesPIX(config)# isakmp key 123456 address 81.81.81.81 netmask 255.255.255.255 no-xauth no-config-mode

[/box]

7. To establish the VPN phase 1 (ISAKMP) the devices at both ends of the tunnel need a matching ISAKMP policy. I’ve already set up my shared secret, the first line lets the other end know that’s how we will be communicating. Then once again I’m using 3DES and SHA. I’m telling the system to use Diffie Hellman group 2 for the secure key exchange, and then binding this policy to the outside interface.

Note: If you are interested on how all this stuff works see here

[box]

PetesPIX(config)# isakmp policy 20 authen pre-share
PetesPIX(config)# isakmp policy 20 encrypt 3des
PetesPIX(config)# isakmp policy 20 hash sha
PetesPIX(config)# isakmp policy 20 group 2
PetesPIX(config)# isakmp enable outside

[/box]

8. Then save the changes with a write mem command.

[box]

PetesPIX# write mem
Building configuration...
Cryptochecksum: 79745c0a 509726e5 b2c66028 021fdc7d

7424 bytes copied in 1.710 secs (7424 bytes/sec)
[OK]
PetesPIX#

[/box]

PIX 500: Configure a site to site VPN from the PDM

1. To connect to the PDM you are going to need two things, an OLD browser (IE6) and an OLD version of Java. Select Wizards > VPN Wizard.

2. Site to Site > Next.

3. Set the Peer (Device at the other end of the tunnel) and a shared secret that you will also use at the other end > Next.

4. Set the policy that will be used for phase 1 > Next.

5. Now the phase 2 policy > Next

6. Enter the network behind the PIX > Next.

7. Enter the network at the far end of the tunnel > Finish.

8. Finish by saving the changes > File > Save running configuration to flash.

Related Articles, References, Credits, or External Links

Set up a PIX Firewall with the PDM

PIX 506E and 501 Firewall Image and PDM Upgrade

Cisco ASA Site to Site VPN’sSite to Site ISAKMP VPN (Main Mode)

Posted on by

KB ID 0000213

Problem

As with most things, before you have a hope of fixing something, you will stand a better chance if you know how it works in the first place. Below is a quick run though of what’s happening with your site to site VPN‘s and how they work.

For the entire process we will have two Cisco ASA 5500 firewalls and a site to site VPN.

Solution

What’s an Initiator and a Responder?

1. Our Laptop 192.168.1.50 wants to talk to a server on the other site at 172.16.1.50

2. To get out of the local network the Laptop goes through the ASA at its local site, The ASA knows that traffic destined for 172.16.1.50 needs to be sent down the VPN tunnel, so it needs to bring up the tunnel. IT BECOMES THE INITIATOR, contacts the ASA on the other site THAT BECOMES THE RESPONDER.

3 Once that’s complete the tunnel is up and traffic can pass.

So how does it bring up the Tunnel?

To establish an ISAKMP VPN tunnel 3 things have to happen.

1. Phase 1 has to complete.

2. Phase 2 has to complete.

3. The Traffic has to be allowed to pass.

VPN Phase 1 (ISAKMP)

This stage brings up the first secure tunnel (eventually there will be three tunnels) and for it to establish the firewalls need to agree what they are going to do to bring up the tunnel, then Secure the tunnel. This process uses SIX MESSAGES (Note: We are dealing to Main Mode here not Aggressive mode). Both firewalls need a matching Phase 1 Policy to continue. And the Policy is proposed in MESSAGE1 and accepted in MESSAGE2.

A Phase 1 policy consists of,

1. The Authentication method (either a pre shared key or an RSA signature is usual).

2. The Encryption method (DES, 3DES, AES, AES-192, or AES-256).

3. The Hashing Method (MD5 or SHA).

4. The Diffie Helman Group (1, 2 or 5 usually).

5. Lifetime (In seconds before phase 1 should be re-established – usually 86400 seconds [1 day]).

MESSAGE 1

The Initiator sends policies that it proposes to use, for phase 1 to the other ASA.

MESSAGE 2

Providing the responder has a matching policy it will accept one of those proposed by the initiator and send it back in message 2.

 

Now the two ends have agreed HOW they will establish phase 1, they then need to agree on a “Shared Key” both ends must use the same shared key, but the shared key cant be sent between them because the network link is not secure. To do this they use a Diffie Hellman key exchange, this uses a mathematical process called modular exponentiation, a simple example of how that works (The math’s involved in a real key exchange are much more complicated!).

How Diffie Hellman works (simply)

Problem Site A and Site B need to use the same secret key (which will be a big long number). they cant send that number to each other because if they do it will be seen.

Solution:

Both sites pick a random number, and they have a common number, this common number can be passed between sites, In our example Site A chooses 4 and Site B chooses 5

Both sites use the common number and raise it by the power of the random number they are using so Site A arrives at 16, and Site B at 32.

The sites then send the number they have arrived at, to the other site.

Each site uses the other sites total and raises it to the power of their original random number, this results in them both having the same key, with only the numbers 2, 16 and 32 being passed between them.

Back to our VPN Tunnel

The next two messages are the initiator and responder swapping their Diffie Hellman information, Each side produces a DH Public Key, and mathematically computes a long number called a “Nonce”

MESSAGE 3

The initiator generates a “Public Key” also called the DH Public Value or Xa It also generates a Nonce or Ni and sends both of them to the responder.

MESSAGE 4

The responder generates a “Public Key” also called the DH Public Value or Xb It also generates a Nonce or Nr and sends both of them to the initiator.

At this point both the initiator and the responder can calculate the DH Shared secret key, they then use the DH Secret Key, the “Shared Secret” that is manually entered onto both peers, and the Nonce from the other peer to create 3 DIGITAL KEYS, because of the nature of Diffie Hellman each end will produce the same keys.

Key 1 = SKEYID_d Used to work out any future IPsec keying Key 2 = SKEYID_a Used for data integrity and authentication (IKE) Key 3 = SKEYID_e Used to encrypt all further IKE traffic.

MESSAGE 5

The initiator now sends its ID to the responder (this is either its IP address or a hostname). It also sends a “Hash” this authenticates the initiator to the responder as its made from the SKEYID, the pre-shared key and other information only known to the two peers.

MESSAGE 6

Message 6 is basically the mirror of Message 5, the responder sends its ID (IP or Hostname) Back the the initiator with its “Hash” and authenticates itself back to the initiator.

At this point both peers recalculate the hash they have received from the other peer, and they should both come out the same, if this happens then the IKE SA’s are established and phase 1 is complete.

So what’s PFS?

Perfect Forward Secrecy is a method by which new keys are generated, each new key is mathematically linked to the key that came before it, the prior key being a “Grandfather” key. With PFS enabled this link is broken so a key can not be forward/reverse engineered to guess a previous/new key value). Every new negotiation produces a new fresh key.

VPN Phase 2

Once Phase 1 has completed the second stage of the VPN can start. Like phase 1 this state also requires messages to be sent between the peers, IPsec usually executes in “Quick mode” this means that there are only 3 MESSAGES.

Note: If PFS is configured only on one end then it will fail at this point with an “Attribute not supported” error.

MESSAGE 1

The Initiator sends another Hash to the responder, this is similar to the one used in phase 1 but also includes info within this message to guarantee integrity.

The Phase 2 proposal includes

1. Encapsulation method either ESP or AH.

2. Hashing method (Integrity checking) either SHA-HMAC or MD5-HMAC.

3. Diffie Hellman Group (1, 2, or 5).

4. The SPI – This number is the LABEL for the end of the tunnel the initiator will use for outbound traffic.

Tunnel mode (Tunnel or Transport). A timeout in seconds is specified, as is the ID (usually the subnet of both ends of the tunnel).

MESSAGE 2

The Responder replies with its own “Hash” with the accepted proposal and its own SPI for outgoing encrypted traffic from the responder, and finally its own Key Exchange Payload.

Once this is complete both peers generate new DH secret keys and combine them with the SKEYID_d key from phase 1 to create keys for IPsec encryption.

MESSAGE 3

The final Message is sent from imitator to responder, and serves to inform the responder that its previous message was received.

Once phase 2 is complete IPsec SA’s have been established and the tunnel is up.

 

Related Articles, References, Credits, or External Links

NA

Troubleshooting Phase 2 Cisco Site to Site (L2L) VPN Tunnels

Posted on by

KB ID 0000625 

Problem

It’s been over two years since I wrote Troubleshooting Phase 1 Cisco Site to Site (L2L) VPN Tunnels. I’ve always meant to come back and write the ‘Phase 2’ article but never got around to it.

This article is NOT intended to be a ‘fix all” for phase 2 problems, it’s designed to point you in the right direction to locate the source of the problem.

Solution

Here’s my fictional VPN setup,

1. Before you start: We are looking at phase 2 problems, MAKE SURE phase 1 has established!

[box]

Petes-ASA>
Petes-ASA> en
Password: ********
Petes-ASA# show crypto isakmp

IKEv1 SAs:

Active SA: 1 Rekey SA: 0 (A tunnel will report 1 Active and 1 Rekey SA during rekey)
Total IKE SA: 1

1 IKE Peer: 234.234.234.234
Type : L2L Role : responder
Rekey : no State : MM_ACTIVE <<<< Phase 1 has established!

[/box]

2. At the first site, issue a ‘show crypto ipsec sa’ command. Note: if you have a lot of tunnels and the output is confusing use a ‘show crypto ipsec sa peer 234.234.234.234’ command instead.

Click for Larger Image

Note: Yes I can zero in on the problem here, but your output may be different (And if you already know why are you reading this!).

3. Check the IP addresses and networks listed highlighted in yellow are correct, then repeat for the ones highlighted in pink (I don’t care if you don’t think it’s pink! I’m a man, I see in 16 colours like a Sinclair ZX Spectrum!). Check the access-list (above shown in blue text) that access-list should be referenced in the crypto map like so;

[box]

Petes-ASA# show run crypto
{Lots of output removed for the sake of space}
crypto map outside_map 1 match address outside_38_cryptomap <<<<Good!!
crypto map outside_map 1 set pfs
crypto map outside_map 1 set peer 234.234.234.234
crypto map outside_map 1 set ikev1 transform-set ESP-3DES-SHA <<<< Only seen after v8.4!
{Lots of output removed for the sake of space}

[/box]

4. Now we need to make sure that the traffic is NOT subject to NAT, issue a “show run nat” command;

[box]

Output with an Operating System Newer than 8.3 

Petes-ASA# show run nat
{Lots of output removed for the sake of space}
nat (inside,outside) source static NETWORK_OBJ_192.168.1.0_24 NETWORK_OBJ_192.168.1.0_24 destination static NETWORK_192.168.2.0_24 NETWORK_OBJ_192.168.2.0_2
{Lots of output removed for the sake of space}
Petes-ASA# show run object network <<<<Lets check those objects exist
object network obj_any
subnet 0.0.0.0 0.0.0.0
object network NETWORK_OBJ_192.168.1.0_24
subnet 192.168.1.0 255.255.255.0
object network NETWORK_OBJ_192.168.2.0_24
subnet 192.168.2.0 255.255.255.0


Output with an Operating System Older than 8.3

Petes-ASA# show run nat
nat (inside) 0 access-list inside_nat0_outbound
nat (inside) 1 192.168.1.0 255.255.255.0
Petes-ASA# show run access-list inside_nat0_outbound <<<<Lets make sure that ACL is correct
access-list inside_nat0_outbound extended permit ip 192.168.1.0 255.255.255.0 192.168.2.0 255.255.255.0

[/box]

5. Now repeat the process at the other end;

Click for Larger Image

6. You will notice I’ve shown the SPI numbers in green, these should match (but be the opposite way round) at both ends. (Geek Note: These denote the TWO tunnels IPSEC brings up inside the original ISAKMP tunnel that it then passes information up one and down the other – like a two lane road).

7. If you compare both outputs look at the pkts encaps (in red) and the pkts decaps (in purple). In this case we can see that the tunnel is working as it should from the 234.234.234.234 site but no traffic is getting encrypted from the 123.123.123.123 site. THAT’S WHERE THE PROBLEM IS.

8. Now you know where the problem is you can issue a “debug crypto ipsec” command there. Then try to bring up the tunnel and analyse the output. Note: If debug shows nothing make sure there is NOT another crypto map pointing to the same subnet, with a different peer.

9. So on our ‘problem’ end we see something like;

So on that firewall, locate the ACL that is being used for the crypto map, and make sure its ‘hit count’ is going up as you try and send traffic over the VPN tunnel. If not then the ACL is wrong, there’s a routing problem or a subnet mask is wrong on the firewalls internal interface.

[box]

Petes-ASA# show run crypto
crypto ipsec ikev1 transform-set ESP-3DES-SHA esp-3des esp-sha-hmac
crypto map outside_map 1 match address outside_1_cryptomap << Here!
crypto map outside_map 1 set pfs
crypto map outside_map 1 set peer 234.234.234.234
crypto map outside_map 1 set ikev1 transform-set ESP-3DES-SHA
crypto map outside_map interface outside
crypto ikev1 enable outside
crypto ikev1 policy 10
authentication pre-share
encryption 3des
hash sha
group 2
lifetime 86400
Petes-ASA# show access-list outside_1_cryptomap
access-list outside_1_cryptomap; 1 element; name hash: 0xcf826bcb
access-list outside_1_cryptomap line 1 extended permit ip 192.168.1.0 255.255.255.0 192.168.2.0 255.255.255.0 (hitcnt=93) 0xf965c6f9

[/box]

10. As a last resort recycle/restart the VPN Tunnel.

Cisco ASA 5500 – Reset / Recycle VPN Tunnels

11. You’ve done your best and still it wont establish! Then I would upgrade the ASA(s) to the latest OS (70% of the calls I log to Cisco TAC for VPN issues are fixed by simply upgrading them, 29% are caused by a configuration error, and 1% need a version of the operating system that has not been released yet). If you’re under warranty or Cisco SmartNet, you can then log a call to Cisco TAC. If not then I would suggest heading over to EE and asking for help. (You might even get hold of me).

Related Articles, References, Credits, or External Links

Troubleshooting Phase 1 Cisco Site to Site (L2L) VPN Tunnels

Cisco ASA Site to Site VPN’s

Cisco ASA5500 Site to Site VPN from ASDM

Cisco ASA 5500 Site to Site VPN (From CLI)

Cisco ASA to Juniper SRX Site to Site VPN

Posted on by

KB ID 0000710

Problem

You want to establish a site to site VPN from a site with a Cisco ASA firewall, to another site running a Juniper SRX firewall. I had to do this this week, and struggled to find any good information to help.

In the example below I’m configuring the whole thing from a laptop (172.16.254.206) that’s on the Juniper’s site. Use the diagram below, and substitute your own IP addresses and subnet addresses, to get a workable solution for your site.

When the process is complete, I will test it by pinging the host behind the Cisco ASA on the remote site (10.254.254.5).

Solution

Before you begin, I will assume both firewalls are functioning properly and the clients behind them can access internet services (where allowed) through them already.

Step 1 – Configure the ASA

Model used Cisco ASA 5505 v8.4 (ASDM 6.4)

1. Connect to the ASDM > Wizards > VPN Wizards > Site-to-site VPN Wizard.

2. Next.

3. Enter the public IP address of the Juniper Firewall > Next, (Note: I’m assuming the VPN is terminated on the outside interface, if not change it).

4. IKE version 1 > Next.

5. Enter the Local (behind the ASA) network > Then the Remote (behind the Juniper) network > Next.

Note: You can type them in, but if you use the pick-list button you can select ‘inside-network’ for the local, and define a network object for the remote network.

6. Enter a pre shared key, (remember this, you need to enter it on the Juniper).

7. Accept the default of 3DES and SHA1 > Next.

8. Enable PFS > Tick the box to exempt traffic from NAT > Next.

9. Review the settings > Finish

11. Save the changes > File > Save running Configuration to Flash.

Step 2 – Configure the Juniper SRX (Route Based VPN)

Model used SRX100B version 11.2R4.3

The SRX support two types of VPN

  1. Route based VPN – VPN selection is done based on the route. In this you define a route pointing to the tunnel interface (st0 interface) bound to the VPN.
  2. Policy based VPN – VPN is selected based on the policy.

12. Log onto the Juniper Web Device Manager.

13. Tasks > Configure VPN > Launch VPN Wizard.

14. Accept the default of Site-to-site > Start.

15. Give the tunnel a name > Set the local zone to trust > Add in the local subnet (behind the Juniper) > Name the Secure Tunnel Interface (just put in a zero) > Set the secure tunnel zone to Untrust > Enter the physical address the VPN will be terminating on, (usually the fe0/0/0.0 interface, but it does not have to be) > Next.

Note: On the Juniper, when specifying a subnet use the short subnet notation, i.e. 192.168.1.0 255.255.255.0 would be 192.168.1.0/24 (if you get stuck use my subnet calculator).

16. Supply the public IP address of the ASA > and add in the subnet at the far end of the tunnel (behind the ASA) > Next.

17. Set the IKE (phase 1) settings to Compatible, Main Mode, enter the same pre shared key you setup in Step 1 (number 6) > Set the IPSEC (phase 2) settings to Compatible, IPsec Perfect Forward Secrecy (PFS) to group 2 > Next.

18. Accept the defaults > Next.

19. Review the settings > Commit.

Step 3 – Additional Steps required (for Cisco ASA)

20. Navigate to IPsec VPN > Auto Tunnel > Phase II > Select your tunnel > Edit > IPsec VPN Options > Tick ‘use proxy identity’ > Enter the local and remote subnets > OK.

21. Navigate to Security > Zones/Screen > Select the untrust zone > Edit > Host Inbound traffic – Interface > Select the physical address that the VPN is terminating on (usually fe-0/0/0.0) > Add IKE as an Interface service > OK.

22. To save the changes > Action > Commit.

23. Test the VPN by attempting to ping a host on the other end.

Juniper SRX Command Line

On the Cisco firewalls I prefer to work at command line. The Juniper Firewall also supports CLI, you can check the VPN config with the following commands;

If you want you can execute the below commands on CLI to get the “set” commands

            show security ike | display set
            show security ipsec | display set
            show | display set | match <external interface configured in ike>
            show | display set | match <st.x>

Above  commands will give you the “set” commands for cli.

Related Articles, References, Credits, or External Links

Special thanks to Kalanidhi Tripathi at JTAC for his assistance.

Juniper KB Articles

 

SRX Getting Started – Configure VPN tunnel for site-to-site connectivity

How to configure IPSec VPN on a J Series or SRX Series device

 

Cisco ASA 5500 – VPN Works in One Direction

Posted on by

KB ID 0000759

Problem

The title of this article can cover a multitude of possible causes, however I recently had a strange problem where a client with a remote site protected by an ASA5505 had a VPN tunnel connected to their main site which had an ASA5510. The tunnel established at phase 1, and phase 2, the main site could talk to the remote site, but the remote site refused to talk back to the main site.

Update 23/04/19: Seen again this time, the ASA at the ‘problem end’ had a static route pointing 10.0.0.0/8 internally, but VPN traffic needed to get to 10.4.0.0/24 at the other end of the VPN tunnel, so traffic was reputed back into the LAN again and dropped.

Update 13/08/14: Seen again, this time from ASA at the problem end, I could ‘ping inside {IP at the remote site}’ and get a response, and the tunnel established. But internal clients could not send traffic over the VPN.

Solution

Usually if you can only “Establish” a tunnel from one side, and it still works, the culprit is normally that PFS has only been specified at one end of the tunnel. On both ends issue a ‘show run crypto map’ command and make sure both ends either use PFS or do not use PFS.

[box]

crypto map outside_map 1 match address outside_1_cryptomap
 crypto map outside_map 1 set pfs
 crypto map outside_map 1 set peer 123.123.123.123 
 crypto map outside_map 1 set ikev1 transform-set ESP-3DES-SHA[/box]

However in this case there was a ‘Rogue NAT entry’ on the ASA5505, that looks like a throwback from an OS upgrade.

[box]

 nat (inside,outside) source static LocalSN LocalSN destination static Site1SN Site1SN
 nat (inside,outside) source static LocalSN LocalSN destination static Site2SN Site2SN
 nat (inside,outside) source static LocalSN LocalSN destination static Site3SN Site3SN
 nat (inside,outside) source static LocalSN LocalSN destination static Site4SN Site4SN
 nat (inside,outside) source dynamic any interface
 nat (inside,outside) source static LocalSN LocalSN destination static Site5SN Site5SN
 !
 object network OBJ-NAT-ALL
 subnet 0.0.0.0 0.0.0.0 
 nat (inside,outside) dynamic interface [/box]


Note: The line in red should not have been there. The last three lines are all you need (Note: your object may be called obj_any).

You can see why it’s causing a problem if you do a packet-trace on some traffic, (see the two examples below).

Packet-Tracer Results (Misconfigured)

[box]

PetesASA# packet-tracer input inside icmp 192.168.2.2 8 0 192.168.1.1

Phase: 1
 Type: ROUTE-LOOKUP
 Subtype: input
 Result: ALLOW
 Config:
 Additional Information:
 in 0.0.0.0 0.0.0.0 outside

Phase: 2
 Type: ACCESS-LIST
 Subtype: log
 Result: ALLOW
 Config:
 access-group inside_access_in in interface inside
 access-list inside_access_in extended permit ip any any
 Additional Information:

Phase: 3
 Type: CONN-SETTINGS
 Subtype:
 Result: ALLOW
 Config:
 class-map class-default
 match any
 policy-map global_policy
 class class-default
 set connection decrement-ttl
 service-policy global_policy global
 Additional Information:

Phase: 4
 Type: NAT
 Subtype:
 Result: ALLOW
 Config:
 nat (inside,outside) source dynamic any interface <Problem!
 Additional Information:
 Dynamic translate 192.168.2.2/0 to 123.123.123.123/21205 <Problem!

Phase: 5
 Type: NAT
 Subtype: per-session
 Result: ALLOW
 Config:
 Additional Information:

Phase: 6
 Type: IP-OPTIONS
 Subtype:
 Result: ALLOW
 Config:
 Additional Information:

Phase: 7
 Type: INSPECT
 Subtype: np-inspect
 Result: ALLOW
 Config:
 class-map inspection_default
 match default-inspection-traffic
 policy-map global_policy
 class inspection_default
 inspect icmp
 service-policy global_policy global
 Additional Information:

Phase: 8
 Type: INSPECT
 Subtype: np-inspect
 Result: ALLOW
 Config:
 Additional Information:

Phase: 9
 Type: NAT
 Subtype: rpf-check
 Result: ALLOW
 Config:
 nat (inside,outside) source dynamic any interface <Problem!
 Additional Information:

Phase: 10
 Type: NAT
 Subtype: per-session
 Result: ALLOW
 Config:
 Additional Information:

Phase: 11
 Type: IP-OPTIONS
 Subtype:
 Result: ALLOW
 Config:
 Additional Information:

Phase: 12
 Type: FLOW-CREATION
 Subtype:
 Result: ALLOW
 Config:
 Additional Information:
 New flow created with id 32065, packet dispatched to next module

Result:
 input-interface: inside
 input-status: up
 input-line-status: up
 output-interface: outside
 output-status: up
 output-line-status: up
 Action: allow

[/box]

Packet-Tracer Results (Configured Correctly)

[box]

PetesASA# packet-tracer input inside icmp 192.168.2.2 8 0 192.168.1.1

Phase: 1
 Type: ROUTE-LOOKUP
 Subtype: input
 Result: ALLOW
 Config:
 Additional Information:
 in 0.0.0.0 0.0.0.0 outside

Phase: 2
 Type: UN-NAT
 Subtype: static
 Result: ALLOW
 Config:
 nat (inside,any) source static NETWORK_OBJ_192.168.2.0_24 NETWORK_OBJ_192.168.2.0_24 destination static NETWORK_OBJ_192.168.1.0_24 NETWORK_OBJ_192.168.1.0_24 no-proxy-arp route-lookup < That's Better!
 Additional Information:
 NAT divert to egress interface outside
 Untranslate 192.168.1.1/0 to 192.168.1.1/0  < That's Better!

Phase: 3
 Type: ACCESS-LIST
 Subtype: log
 Result: ALLOW
 Config:
 access-group inside_access_in in interface inside
 access-list inside_access_in extended permit ip any any
 Additional Information:

Phase: 4
 Type: CONN-SETTINGS
 Subtype:
 Result: ALLOW
 Config:
 class-map class-default
 match any
 policy-map global_policy
 class class-default
 set connection decrement-ttl
 service-policy global_policy global
 Additional Information:

Phase: 5
 Type: NAT
 Subtype:
 Result: ALLOW
 Config:
 nat (inside,any) source static NETWORK_OBJ_192.168.2.0_24 NETWORK_OBJ_192.168.2.0_24 destination static NETWORK_OBJ_192.168.1.0_24 NETWORK_OBJ_192.168.1.0_24 no-proxy-arp route-lookup < That's Better!
 Additional Information:
 Static translate 192.168.2.2/0 to 192.168.2.2/0 < That's Better!

Phase: 6
 Type: NAT
 Subtype: per-session
 Result: ALLOW
 Config:
 Additional Information:

Phase: 7
 Type: IP-OPTIONS
 Subtype:
 Result: ALLOW
 Config:
 Additional Information:

Phase: 8
 Type: INSPECT
 Subtype: np-inspect
 Result: ALLOW
 Config:
 class-map inspection_default
 match default-inspection-traffic
 policy-map global_policy
 class inspection_default
 inspect icmp
 service-policy global_policy global
 Additional Information:

Phase: 9
 Type: INSPECT
 Subtype: np-inspect
 Result: ALLOW
 Config:
 Additional Information:

Phase: 10
 Type: VPN
 Subtype: encrypt
 Result: ALLOW
 Config:
 Additional Information:

Phase: 11
 Type: NAT
 Subtype: rpf-check
 Result: ALLOW
 Config:
 nat (inside,any) source static NETWORK_OBJ_192.168.2.0_24 NETWORK_OBJ_192.168.2.0_24 destination static NETWORK_OBJ_192.168.1.0_24 NETWORK_OBJ_192.168.1.0_24 no-proxy-arp route-lookup  < That's Better!
 Additional Information:

Phase: 12
 Type: VPN
 Subtype: ipsec-tunnel-flow
 Result: ALLOW
 Config:
 Additional Information:

Phase: 13
 Type: NAT
 Subtype: per-session
 Result: ALLOW
 Config:
 Additional Information:

Phase: 14
 Type: IP-OPTIONS
 Subtype:
 Result: ALLOW
 Config:
 Additional Information:

Phase: 15
 Type: FLOW-CREATION
 Subtype:
 Result: ALLOW
 Config:
 Additional Information:
 New flow created with id 33263, packet dispatched to next module

Result:
 input-interface: inside
 input-status: up
 input-line-status: up
 output-interface: outside
 output-status: up
 output-line-status: up
 Action: allow

[/box]

Related Articles, References, Credits, or External Links

Cisco ASA Site to Site VPN’s Site to Site ISAKMP VPN (Main Mode)

Original Article Written 05/02/13