![]() ![]() IKMP_NO_ERROR_NO_TRANS indicates a matching transform set was not found Please note that you cannot limit the debug output to a specific tunnel. Debug level 5 should be sufficient for most troubleshooting however level 7 provides more detailed information if necessary. ![]() The debug crypto isakmp 5 command will display real time information on every step of the Phase I connection. OAK_MM_KEY_AUTH The ISAKMP SA has been authenticated. OAK_MM_KEY_EXCH The peers have exchanged DH public keys and have generated a shared secret. MM_WAIT_MSG The firewall is waiting on the remote end device to respond with DH and public key. ![]() Phase I will be in this state after packet 1 and packet 2 exchange of the Main Mode negotiation (see above). OAK_MM_SA_SETUP The peers have agreed on parameters for the ISAKMP Indication that a failure of tunnel establishment for In this state for longer than a few seconds, this is an OAK_MM_No_STATE This is the initial state of Phase I. More specific information can be found by running a debug(discussed later). This will give you an indication of where the problem has occurred. If Phase I does not complete, refer to the table below to find out exactly what state the Phase I connection is currently in. A state of MM_Active indicates that Phase I was successfully completed. Show crypto isakmp sa detail – This command will display the state of Phase I of the IPSEC tunnel. To view a specific ISAKMP policy type show run isakmp | grep This will show the isakmp policies for all VPN connections. #isakmp policy 20 authentication pre-share When a Phase I connection is being established, configured ISAKMP policies will be tried one at a time until a match is found. Phase I is not configured on a per connection basis. The first 2 octets of IPs have been replaced with "y.y." Step 7 If CA authentication is configured with the various crypto ca commands, the router uses public and private keys previously configured, obtains the CA's public certificate, gets a certificate for its own public key, and then uses the key to negotiate an IKE SA, which in turn is used to establish an IPSec SA to encrypt and transmit the packet. Step 6 If the IKE SA has not been set up, Cisco IOS software checks to see if certification authority (CA) has been configured to establish an IKE policy. Step 5 If the IKE SA has been set up, the IKE SA governs negotiation of the IPSec SA as specified in the IKE policy configured by the crypto isakmp policy command, the packet is encrypted by IPSec, and it is transmitted. Step 4 If the SA has not been established, Cisco IOS software checks to see if an IKE SA has been configured and set up. ![]() Step 3 If the SA has already been established by manual configuration using the crypto ipsec transform-set and crypto map commands or has been previously set up by IKE, the packet is encrypted based on the policy specified in the crypto map and is transmitted out of the interface. Step 2 Cisco IOS software checks to see if IPSec SAs have been established. Step 1 Access lists applied to an interface and crypto map are used by Cisco IOS software to select interesting traffic to be encrypted. The SA represents a unidirectional instance of a security policy for a given connection. Each device must agree on the policies or rules of the conversation by negotiating these policies with their potential peers. In order to have an IPSEC conversation, you first need a security association. It is important to understand that AH encapsulates the IP packet but does not encrypt it.ĮSP communicates over IP 50 and provides the same service as AH in addition to providing data confidentiality by encrypting the original payload and encapsulating the packet. AH communicates over IP 51 and provides data authentication, integrity, and replay protection (for man in the middle attacks), but does not provide confidentiality. Security Protocols consist of AH (Authentication Header) and ESP (Encapsulating Security Payload). ISAKMP defines the procedures and packet formats used to establish, negotiate, and modify Security Associations. IPSEC consists of Security Protocols (AH and ESP), Key Management (ISAKMP, IKE, and SKEME), and Algorithms (3DES, AES256, etc). IPSEC is a suite of protocols, defined in RFC 2401, that is used to protect information as it travels from one private network to another private network over a public network. This is a quick overview of IPSEC and is by no means a complete detailed guide. It is important to understand how IPSEC works in order to understand how to troubleshoot a VPN connection. ![]()
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