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Manual Chapter : Setting Up IPsec To Use NAT Traversal on Both Sides of the WAN

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Manual Chapter

Setting Up IPsec To Use NAT Traversal on Both Sides of the WAN

Overview: Setting up IPsec to use NAT traversal on both sides of the WAN

When you are using IPsec to secure WAN traffic, you can set up an IPsec tunnel with NAT traversal (NAT-T) to get around a firewall or other NAT device. This implementation describes how to set up the IPsec tunnel when you have a NAT device on both sides of the tunnel.
The following illustration shows a network configuration with a firewall on both sides of the WAN.
Example of an IPsec deployment with NAT-T on both sides of the WAN
Example of an IPsec deployment with NAT-T on both sides of the WAN

Before you begin IPsec configuration

Before you configure IPsec on a BIG-IP® device, make sure that you have completed the following general prerequisites.
  • You must have an existing routed IP network between the two locations where the BIG-IP devices will be installed.
  • The BIG-IP hardware is installed with an initial network configuration applied.
  • The management IP address is configured on the BIG-IP system.
  • If you are using NAT traversal, forward UDP ports 500 and 4500 to the BIG-IP system behind each firewall.
  • Verify the connectivity between the client or server and its BIG-IP device, and between each BIG-IP device and its gateway. You can use
    ping
     to test connectivity.

Task summary

When you are configuring an IPsec tunnel, you must repeat the configuration tasks on the BIG-IP systems on both sides of the WAN.

Creating a forwarding virtual server for IPsec

For IPsec, you create a forwarding (IP) type of virtual server to intercept IP traffic and direct it over the tunnel. With a forwarding (IP) virtual server, destination address translation and port translation are disabled.
  1. On the Main tab, click
    Local Traffic
    Virtual Servers
    .
    The Virtual Server List screen opens.
  2. Click
    Create
    .
    The New Virtual Server screen opens.
  3. In the
    Name
     field, type a unique name for the virtual server.
  4. From the
    Type
     list, select
    Forwarding (IP)
    .
  5. In the
    Destination Address/Mask
     field, type a wildcard network address in CIDR format, such as
    0.0.0.0/0
     for IPv4 or
    ::/0
     for IPv6, to accept any traffic.
  6. From the
    Service Port
     list, select
    *All Ports
    .
  7. From the
    Protocol
     list, select
    *All Protocols
    .
  8. From the
    VLAN and Tunnel Traffic
     list, retain the default selection,
    All VLANs and Tunnels
    .
  9. Click
    Finished
    .

Creating an IPsec tunnel with NAT-T on both sides

You can create an IPsec tunnel to securely transport application traffic across the WAN. You must configure the IPsec tunnel on the BIG-IP systems on both sides of the WAN.
When you create an IKEv1 or IKEv2 peer for NAT traversal (NAT-T), the key configuration detail is that the
Remote Address
 setting is the public IP address of the firewall or other NAT device (not the IP address of the remote BIG-IP system). Also, you must turn on NAT traversal. You can customize the remaining settings to conform to your network.
For the IKE peer negotiations to be successful, the IKE Phase 1 settings (on the IKE peer) and the IKE Phase 2 settings (in an IPsec policy) must be the same on the BIG-IP systems at both ends of the IPsec tunnel.
You must perform this procedure twice, once on each BIG-IP system on either side of the WAN. For each step in the procedure where you need to type an IP address, the step shows two sample IP addresses -- one that you configure on the BIG-IP system located in Site A and the other that you configure on the BIG-IP system located in Site B.
  1. Create an IKE peer that specifies the other end of the IPsec tunnel.
    1. On the Main tab, click
      Network
      IPsec
      IKE Peers
      .
    2. Click the
      Create
       button.
    3. In the
      Name
       field, type a unique name for the IKE peer.
    4. In the
      Remote Address
       field, type the public IP address of the firewall or other NAT device that is between the WAN and the remote BIG-IP system. In other words, this is the IP address that the BIG-IP system address is translated to, not the original BIG-IP source address.
      This address is the IP address of the remote peer, and must match the value of the
      Tunnel Remote Address
       setting in the relevant IPsec policy.
      For example, the peer remote addresses for the BIG-IP systems in Site A and Site B are as follows.
      Location
      Remote (Peer) Address
      Site A
      165.160.15.20
      Site B
      203.0.113.2
      This screen snippet shows the peer
      Remote Address
       setting at Site A. Screen showing Site A Remote Address setting
    5. For the IKE Phase 1 Algorithms area, retain the default values, or select the options that are appropriate for your deployment.
    6. In the IKE Phase 1 Credentials area, for the
      Authentication Method
       setting, select either
      Preshared Key
       or
      RSA Signature
      , and specify additional information in the fields that appear.
      For example, if you select
      Preshared Key
      , type the key in the
      Preshared Key
       field that becomes available.
      IKE Phase 1 Preshared Key setting example
      The key you type must be the same at both ends of the tunnel.
    7. From the
      NAT Traversal
       list, select
      On
      .
      NAT Traversal setting example
    8. Click
      Finished
      .
  2. Create a custom IPsec policy that uses Tunnel mode and has the same remote IP address as the IKE peer.
    1. On the Main tab, click
      Network
      IPsec
      IPsec Policies
      .
    2. Click the
      Create
       button.
    3. In the
      Name
       field, type a unique name for the policy.
    4. For the
      IPsec Protocol
       setting, retain the default selection,
      ESP
      .
    5. From the
      Mode
       list, select
      Tunnel
      .
      The screen refreshes to show additional related settings.
    6. In the
      Tunnel Local Address
       field, type the local IP address of the system you are configuring.
      For example, the tunnel local addresses for the BIG-IP systems in Site A and Site B are as follows.
      Location
      Tunnel Local Address
      Site A
      10.100.20.3
      Site B
      10.102.20.5
    7. In the
      Tunnel Remote Address
       field, type the public IP address of the firewall or other NAT device that is between the WAN and the remote BIG-IP system. In other words, this is the IP address that the source IP address of the BIG-IP system is translated to, and not the original source address.
      This address must match the value of the
      Remote Address
       setting for the relevant IKE peer.
      For example, the tunnel remote addresses for the BIG-IP systems in Site A and Site B are as follows.
      Location
      Tunnel Remote Address
      Site A
      165.160.15.20
      Site B
      203.0.113.2
      This screen snippet shows the tunnel settings at Site A. Example of tunnel settings at Site A
    8. For the
      Authentication Algorithm
       setting, retain the default value, or select the algorithm appropriate for your deployment.
    9. For the
      Encryption Algorithm
       setting, retain the default value, or select the algorithm appropriate for your deployment.
    10. For the
      Perfect Forward Secrecy
       setting, retain the default value, or select the option appropriate for your deployment.
    11. Click
      Finished
      .
  3. Create a bidirectional traffic selector that uses the custom IPsec policy you created.
    The traffic selector filters the application traffic based on the source and destination IP addresses you specify.
    1. On the Main tab, click
      Network
      IPsec
      Traffic Selectors
      .
    2. Click
      Create
      .
    3. In the
      Name
       field, type a unique name for the traffic selector.
    4. For the
      Order
       setting, retain the default value.
    5. For the
      Source IP Address
       setting, in the
      Address
       field, type the IP address from which the application traffic originates.
      For example, the source IP addresses for the BIG-IP systems in Site A and Site B are as follows.
      Location
      Source IP Address
      Site A
      10.100.20.50
      Site B
      10.102.20.10
    6. In the
      Destination IP Address
       setting
      Address
       field, type the final IP address for which the application traffic is destined.
      For example, the source IP addresses for the BIG-IP systems in Site A and Site B are as follows.
      Location
      Destination IP Address
      Site A
      10.102.20.10
      Site B
      10.100.20.50
    7. For the
      Action
       setting, retain the default value,
      Protect
      .
    8. From the
      IPsec Policy Name
       list, select the name of the custom IPsec policy that you just created.
      This portion of a screen is an example of the completed Traffic Selector screen at Site A. Example of completed Traffic Selector screen
    9. Click
      Finished
      .
  4. Repeat this task on the BIG-IP system on the other side of the WAN.
You have now created an IPsec tunnel through which traffic travels in both directions across the WAN through firewalls on both sides.

Verifying IPsec connectivity for Tunnel mode

After you have configured an IPsec tunnel and before you configure additional functionality, you can verify that the tunnel is passing traffic.
Only data traffic matching the traffic selector triggers the establishment of the tunnel.
  1. Access the
    tmsh
     command-line utility.
  2. Before sending traffic, type this command at the prompt.
    tmsh modify net ipsec ike-daemon ikedaemon log-level debug
    This command increases the logging level to display the messages that you want to view.
  3. Send data traffic to the destination IP address specified in the traffic selector.
  4. For an IKEv1 configuration, check the IKE Phase 1 negotiation status by typing this command at the prompt.
    racoonctl -l show-sa isakmp
    This example shows a result of the command.
    Destination
     is the tunnel remote IP address.
    
Destination       Cookies               ST S  V E Created            Phase2
165.160.15.20.500 98993e6 . . . 22c87f1  9 I 10 M 2012-06-27 16:51:19     1
    This table shows the legend for interpreting the result.
    Column
    Displayed
    Description
    ST (Tunnel Status)
    1
    Start Phase 1 negotiation
    2
    msg 1 received
    3
    msg 1 sent
    4
    msg 2 received
    5
    msg 2 sent
    6
    msg 3 received
    7
    msg 3 sent
    8
    msg 4 received
    9
    isakmp tunnel established
    10
    isakmp tunnel expired
    S
    I
    Initiator
    R
    Responder
    V (Version Number)
    10
    ISAKMP version 1.0
    E (Exchange Mode)
    M
    Main (Identity Protection)
    A
    Aggressive
    Phase2
    <n>
    Number of Phase 2 tunnels negotiated with this IKE peer
  5. For an IKEv1 configuration, check the IKE Phase 2 negotiation status by typing this command at the prompt.
    racoonctl -ll show-sa internal
    This example shows a result of this command.
    Source
     is the tunnel local IP address.
    Destination
     is the tunnel remote IP address.
     
Source            Destination           Status         Side
10.100.20.3       165.160.15.20         sa established [R]
    This table shows the legend for interpreting the result.
    Column
    Displayed
    Side
    I (Initiator)
    R (Responder)
    Status
    init
    start
    acquire
    getspi sent
    getspi done
    1st msg sent
    1st msg recvd
    commit bit
    sa added
    sa established
    sa expired
  6. To verify the establishment of dynamic negotiated Security Associations (SAs), type this command at the prompt.
    tmsh show net ipsec ipsec-sa
    For each tunnel, the output displays IP addresses for two IPsec SAs, one for each direction, as shown in the example. 
    
IPsec::SecurityAssociations
10.100.20.3 -> 165.160.15.20 SPI(0x7b438626) in esp (tmm: 6)
165.160.15.20 -> 10.100.20.3 SPI(0x5e52a1db) out esp (tmm: 5)
  7. To display the details of the dynamic negotiated Security Associations (SAs), type this command at the prompt.
    tmsh show net ipsec ipsec-sa all-properties
    For each tunnel, the output displays the details for the IPsec SAs, as shown in the example. 
    
IPsec::SecurityAssociations
165.160.15.20 -> 10.100.20.3
-----------------------------------------------------------------------------
  tmm: 2                                                             
  Direction: out;  SPI: 0x6be3ff01(1810104065);  ReqID: 0x9b0a(39690)
  Protocol: esp;  Mode: tunnel;  State: mature                       
  Authenticated Encryption : aes-gmac128                             
  Current Usage: 307488 bytes                                        
  Hard lifetime: 94 seconds; unlimited bytes                         
  Soft lifetime: 34 seconds; unlimited bytes                         
  Replay window size: 64                                          
  Last use: 12/13/2012:10:42                        Create:  12/13/2012:10:39
  8. To display the details of the IKE-negotiated SAs (IKEv2), type this command at the prompt.
    tmsh show net ipsec ike-sa all-properties
  9. To filter the Security Associations (SAs) by traffic selector, type this command at the prompt.
    tmsh show net ipsec ipsec-sa traffic-selector ts_codec
    You can also filter by other parameters, such as SPI (
    spi
    ), source address (
    src_addr
    ), or destination address (
    dst_addr
    )
    The output displays the IPsec SAs that area associated with the traffic selector specified, as shown in the example. 
    
IPsec::SecurityAssociations
10.100.115.12  ->  10.100.15.132  SPI(0x2211c0a9)  in  esp  (tmm: 0)
10.100.15.132  ->  10.100.115.12  SPI(0x932e0c44)  out  esp  (tmm: 2)
  10. Check the IPsec stats by typing this command at the prompt.
    tmsh show net ipsec-stat
    If traffic is passing through the IPsec tunnel, the stats will increment. 
     
-------------------------------------------------------------------
Net::Ipsec
Cmd Id           Mode  Packets In  Bytes In  Packets Out  Bytes Out
-------------------------------------------------------------------
0           TRANSPORT           0         0            0          0
0           TRANSPORT           0         0            0          0
0              TUNNEL           0         0            0          0
0              TUNNEL           0         0            0          0
1              TUNNEL      353.9K    252.4M        24.9K       1.8M
2              TUNNEL      117.9K     41.0M       163.3K      12.4M
  11. If the SAs are established, but traffic is not passing, type one of these commands at the prompt.


    tmsh delete net ipsec ipsec-sa (IKEv1)


    tmsh delete net ipsec ike-sa (IKEv2)

    This action deletes the IPsec tunnels. Sending new traffic triggers SA negotiation and establishment.
  12. If traffic is still not passing, type this command at the prompt.
    racoonctl flush-sa isakmp
    This action brings down the control channel. Sending new traffic triggers SA negotiation and establishment.
  13. View the
    /var/log/racoon.log
     to verify that the IPsec tunnel is up.
    These lines are examples of the messages you are looking for.
    
2012-06-29 16:45:13: INFO: ISAKMP-SA established 10.100.20.3[500]-165.160.15.20[500] spi:3840191bd045fa51:673828cf6adc5c61
2012-06-29 16:45:14: INFO: initiate new phase 2 negotiation: 10.100.20.3[500]<=>165.160.15.20[500]
2012-06-29 16:45:14: INFO: IPsec-SA established: ESP/Tunnel 165.160.15.20[0]->10.100.20.3[0] spi=2403416622(0x8f413a2e)
2012-06-29 16:45:14: INFO: IPsec-SA established: ESP/Tunnel 10.100.20.3[0]->165.160.15.20[0] spi=4573766(0x45ca46
  14. To turn on IKEv2 logging on a production build, complete these steps.
    If you are using IKEv2, you can skip these steps; the BIG-IP system enables IPsec logging by default.
    1. Configure the log publisher for IPsec to use.
       
      
% tmsh create sys log-config publisher ipsec { destinations add { local-syslog }} 
% tmsh list sys log-config publisher ipsec
sys log-config publisher ipsec {
    destinations {
        local-syslog { }
    }
}
    2. Attach the log publisher to the
      ike-daemon
       object.
      tmsh modify net ipsec ike-daemon ikedaemon log-publisher ipsec
  15. For protocol-level troubleshooting, you can increase the debug level by typing this command at the prompt.
    tmsh modify net ipsec ike-daemon ikedaemon log-level debug2
    Use this command only for debugging. It creates a large log file, and can slow the tunnel negotiation.
    Using this command flushes existing SAs.
  16. After you view the results, return the debug level to normal to avoid excessive logging by typing this command at the prompt.
    tmsh modify net ipsec ike-daemon ikedaemon log-level info
    Using this command flushes existing SAs.
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