Tag Archives: Cisco ASA

ISAKMP (IKE Phase 1) Status Messages MM_WAIT_MSG#

I’ve been meaning to copy this back here but haven’t had the chance until now. I reference this so much, figured it’d have stuck in my mind by now… Anyway, this is one of the best resources for quick analysis troubleshooting of MM_WAIT_MSG errors on VPN tunnels for Cisco ASA / PIX from https://www.tunnelsup.com/isakmp-ike-phase-1-status-messages/.

ISAKMP (IKE Phase 1) Negotiations States

The MM_WAIT_MSG state can be an excellent clue into why a tunnel is not forming. If your firewall is hanging at a specific state review this graph below to find where along the path the VPN is failing.

ASA ISAKMP STATES

Graph source: tunnelsup.com

These are the possible ISAKMP negotiation states on an ASA firewall. ISAKMP stands for: The Internet Security Association and Key Management Protocol

  • MM_WAIT_MSG2 Initiator Initial DH public key sent to responder. Awaiting initial contact reply from other side. Initiator sends encr/hash/dh ike policy details to create initial contact. Initiator will wait at MM_WAIT_MSG2 until it hears back from its peer. If stuck here it usually means the other end is not responding. This could be due to no route to the far end or the far end does not have ISAKMP enabled on the outside or the far end is down.
  • MM_WAIT_MSG3 Receiver Receiver is sending back its IKE policy to the initiator. Initiator sends encr/hash/dh ike policy details to create initial contact. Initiator will wait at MM_WAIT_MSG2 until it hears back from its peer. Hang ups here may also be due to mismatch device vendors, a router with a firewall in the way, or even ASA version mismatches.
  • MM_WAIT_MSG4 Initiator Initiator is sending the Pre-Shared-Key hash to its peer. Initiator sends a hash of its PSK. Initiator will stay at MSG4 until it gets a PSK back from its peer. If the receiver is missing a tunnel group or PSK the initiator will stay at MM_WAIT_MSG4
  • MM_WAIT_MSG5 Receiver Receiver is sending its PSK hash to its peer. Receiver does not yet check if PSK hashes match. If receiver has a tunnel-group and PSK configured for this peer it will send the PSK hash to the peer. If PSKs don’t match, receiver will stay at MM_WAIT_MSG5. I have also seen the tunnel stop here when NAT-T was on when it needed to be turned off.
  • MM_WAIT_MSG6 Initiator Initiator checks if PSK hashes match. If PSK keys match, Initiator becomes MM_ACTIVE and lets receiver know of match. If PSK doesn’t match, initiator stays at MM_WAIT_MSG6. I have also seen the tunnel stop here when NAT-T was on when it needed to be turned off. However, if the state goes to MSG6 then the ISAKMP gets reset that means phase 1 finished but phase 2 failed. Check that IPSEC settings match in phase 2 to get the tunnel to stay at MM_ACTIVE.
  • AM_ACTIVE / MM_ACTIVE The ISAKMP negotiations are complete. Phase 1 has successfully completed.

PIX ISAKMP STATES

    • MM_NO_STATE

ISAKMP SA has been created but nothing else has happened yet.

    • MM_SA_SETUP

The peers have agreed on parameters for the ISAKMP SA.

    • MM_KEY_EXCH

The peers have exchanged Diffie-Hellman public keys and have generated a shared secret. The I SAKMP SA remains unauthenticated.

    • MM_KEY_AUTH

The ISAKMP SA has been authenticated. If the router initiated this exchange, this state trans itions immediately to QM_IDLE and a Quick mode exchange begins.

    • AG_NO_STATE

The ISAKMP SA has been created but nothing else has happened yet.

    • AG_INIT_EXCH

The peers have done the first exchange in Aggressive mode but the SA is not authenticated.

    • AG_AUTH

The ISAKMP SA has been authenticated. If the router initiated this exchange, this state transitions immediately to QM_IDLE and a Quick mode exchange begins.

    • QM_IDLE

The ISAKMP negotiations are complete. Phase 1 successfully completed. It remains authenticated with its peer and may be used for subsequent Quick mode exchanges.

What is the difference between MM and AM?

Main mode vs Aggressive mode. Here is a image taken from Cisco’s website to show the difference.

Graphic source: tunnelsup.com

As you can see the Main mode is the same as the flowchart at the top of the page. Aggressive mode only uses 4 steps to establish the tunnel.

Troubleshooting ISAKMP Or Phase 1 VPN connections

When troubleshooting VPNs, a very common problem is phase 1 not establishing correctly. Here’s a quick checksheet to make sure you have the configuration correct.

  • Verify ISAKMP parameters match exactly.
  • Verify pre-shared-keys match exactly.
  • Check that each side has a route to the peer address that you are trying to form a tunnel with.
  • Verify ISAKMP is enabled on the outside interfaces.
  • Is ESP traffic permitted in through the outside interface?
  • Is UDP port 500 open on the outside ACL?
  • Some situations require that UDP port 4500 is open for the outside.

Warning, DHCP pool range is limited to 128 addresses

For all ASA models, the maximum number of DHCP client addresses varies depending on the license:

  • If the limit is 10 hosts, the maximum available DHCP pool is 32 addresses.
  • If the limit is 50 hosts, the maximum available DHCP pool is 128 addresses.
  • If the number of hosts is unlimited, the maximum available DHCP pool is 256 addresses.

That’s annoying.

Configure Cisco ASA to Capture Specific Port Traffic

On a Cisco ASA you can configure capturing of data to allow for deeper troubleshooting of issues. With the recent issue of the Heartbleed bug, I needed a way to capture HTTPS traffic and inspect remote hosts for the vulnerability. If the site was vulnerable, I would create a temporary block until that site patched.

On the Cisco ASA I setup an access-list:

access-list heartbleed line 1 extended permit tcp any any eq https

I create a capture:

capture heartbleed access-list heartbleed interface inside

Then I can view the capture:

show capture heartbleed

Example output of the above command:

1025: 09:52:27.882385 10.147.204.104.55665 > 74.125.228.5.443: . ack 3734113485 win 64860
1026: 09:52:27.882858 192.168.1.104.55666 > 74.125.228.5.443: . ack 3798098736 win 64860
1027: 09:52:27.883239 192.168.1.104.55666 > 74.125.228.5.443: . ack 3798101496 win 64860
1028: 09:52:27.883438 192.168.1.104.55666 > 74.125.228.5.443: . ack 3798104256 win 64860

Alternatively, while the capture is enabled it is accessible via the web interface of the ASA.

https://192.168.1.1/admin/capture/heartbleed

Test Cisco ASA VPN Authentication

Had an issue with a user that was failing to log into the VPN from remote.  Couldn’t initially figure it out while at home while troubleshooting the authentication.  So here’s how to test authentication from the Cisco ASA CLI.

ciscoasa# test aaa-server authentication AUTH2K8 host 192.168.1.2 username rkreider password s3cr3t

The blue highlights are values that need specified. If not sure of the AAA-SERVER, use the following command to list all the authentication servers.

ciscoasa# show aaa-server

This lists all the aaa-servers; to narrow it down, as in my case, I specified some additional arguments.

ciscoasa# show aaa-server authentication protocol nt

Here is a list of available protocols.

ciscoasa# show aaa-server protocol ?

  http-form  Protocol HTTP form-based
  kerberos   Protocol Kerberos
  ldap       Protocol LDAP
  nt         Protocol NT
  radius     Protocol RADIUS
  sdi        Protocol SDI
  tacacs+    Protocol TACACS+

So the output from showing the aaa-server type of NT is follows for me.

Server Group:    AUTH2K8
Server Protocol: nt
Server Address:  192.168.1.2
Server port:     139
Server status:   ACTIVE, Last transaction at 13:16:58 EDT Wed Mar 26 2014
Number of pending requests              0
Average round trip time                 0ms
Number of authentication requests       435
Number of authorization requests        0
Number of accounting requests           0
Number of retransmissions               0
Number of accepts                       389
Number of rejects                       31
Number of challenges                    0
Number of malformed responses           0
Number of bad authenticators            0
Number of timeouts                      15
Number of unrecognized responses        0

I used the highlighted values in my test case. Again, here is my command.

ciscoasa# test aaa-server authentication AUTH2K8 host 192.168.1.2 username rkreider password s3cr3t
INFO: Attempting Authentication test to IP address <192.168.1.2> (timeout: 12 seconds)
ERROR: Authentication Rejected: AAA failure

ciscoasa# test aaa-server authentication AUTH2K8 host 192.168.1.2 username rkreider password sup3rs3cr3t
INFO: Attempting Authentication test to IP address <192.168.1.2> (timeout: 12 seconds)
INFO: Authentication Successful

My issue was actually related to a setting on the account profile in Active Directory restricting server logons which inherently prevented authentication from working.