Because IKE negotiations must be protected, each IKE negotiation begins by agreement of both peers on a common (shared) IKE policy. This policy states which security parameters will be used to protect subsequent IKE negotiations and mandates how the peers are authenticated.

After the two peers agree upon a policy, the security parameters of the policy are identified by an SA established at each peer, and these SAs apply to all subsequent IKE traffic during the negotiation.

You can configure multiple, prioritized policies on each peer--each with a different combination of parameter values. However, at least one of these policies must contain exactly the same encryption, hash, authentication, and Diffie-Hellman parameter values as one of the policies on the remote peer. For each policy that you create, you assign a unique priority (1 through 10,000, with 1 being the highest priority).

Note

If you are interoperating with a device that supports only one of the values for a parameter, your choice is limited to the value supported by the other device. Aside from this limitation, there is often a trade-off between security and performance, and many of these parameter values represent such a trade-off. You should evaluate the level of security risks for your network and your tolerance for these risks.

When the IKE negotiation begins, IKE searches for an IKE policy that is the same on both peers. The peer that initiates the negotiation will send all its policies to the remote peer, and the remote peer will try to find a match. The remote peer looks for a match by comparing its own highest priority policy against the policies received from the other peer. The remote peer checks each of its policies in order of its priority (highest priority first) until a match is found.

A match is made when both policies from the two peers contain the same encryption, hash, authentication, and Diffie-Hellman parameter values, and when the remote peer's policy specifies a lifetime that is less than or equal to the lifetime in the policy being compared. (If the lifetimes are not identical, the shorter lifetime--from the remote peer's policy--will be used.)

If a match is found, IKE will complete negotiation, and IPsec security associations will be created. If no acceptable match is found, IKE refuses negotiation and IPsec will not be established.

Note	Depending on which authentication method is specified in a policy, additional configuration might be required. If a peer's policy does not have the required companion configuration, the peer will not submit the policy when attempting to find a matching policy with the remote peer.

You should set the ISAKMP identity for each peer that uses preshared keys in an IKE policy.

When two peers use IKE to establish IPsec SAs, each peer sends its identity to the remote peer. Each peer sends either its hostname or its IPv6 address, depending on how you have set the ISAKMP identity of the router.

By default, a peer's ISAKMP identity is the IPv6 address of the peer. If appropriate, you could change the identity to be the peer's hostname instead. As a general rule, set the identities of all peers the same way--either all peers should use their IPv6 addresses or all peers should use their hostnames. If some peers use their hostnames and some peers use their IPv6 addresses to identify themselves to each other, IKE negotiations could fail if the identity of a remote peer is not recognized and a DNS lookup is unable to resolve the identity.

Perform this task to create an IKE policy and a preshared key in IPv6.

You likely do not need to configure aggressive mode in a site-to-site scenario. The default mode is typically used.

Perform this task to define an IPsec transform set. A transform set is a combination of security protocols and algorithms that is acceptable to the IPsec routers.

Sample Output from the show crypto ipsec sa Command

The following is sample output from the show crypto ipsec sacommand:

Router# show crypto ipsec sa
interface: Tunnel0
     Crypto map tag: Tunnel0-head-0, local addr 3FFE:2002::A8BB:CCFF:FE01:9002
    protected vrf: (none)
    local  ident (addr/mask/prot/port): (::/0/0/0)
    remote ident (addr/mask/prot/port): (::/0/0/0)
    current_peer 3FFE:2002::A8BB:CCFF:FE01:2C02 port 500
      PERMIT, flags={origin_is_acl,}
     #pkts encaps: 133, #pkts encrypt: 133, #pkts digest: 133
     #pkts decaps: 133, #pkts decrypt: 133, #pkts verify: 133
     #pkts compressed: 0, #pkts decompressed: 0
     #pkts not compressed: 0, #pkts compr. failed: 0
     #pkts not decompressed: 0, #pkts decompress failed: 0
     #send errors 60, #recv errors 0
      local crypto endpt.: 3FFE:2002::A8BB:CCFF:FE01:9002,
      remote crypto endpt.: 3FFE:2002::A8BB:CCFF:FE01:2C02
      path mtu 1514, ip mtu 1514
      current outbound spi: 0x28551D9A(676666778)
      inbound esp sas:
       spi: 0x2104850C(553944332)
         transform: esp-des ,
         in use settings ={Tunnel, }
         conn id: 93, flow_id: SW:93, crypto map: Tunnel0-head-0
         sa timing: remaining key lifetime (k/sec): (4397507/148)
         IV size: 8 bytes
         replay detection support: Y
         Status: ACTIVE
      inbound ah sas:
       spi: 0x967698CB(2524354763)
         transform: ah-sha-hmac ,
         in use settings ={Tunnel, }
         conn id: 93, flow_id: SW:93, crypto map: Tunnel0-head-0
         sa timing: remaining key lifetime (k/sec): (4397507/147)
         replay detection support: Y
         Status: ACTIVE
      inbound pcp sas:
      outbound esp sas:
       spi: 0x28551D9A(676666778)
         transform: esp-des ,
         in use settings ={Tunnel, }
         conn id: 94, flow_id: SW:94, crypto map: Tunnel0-head-0
         sa timing: remaining key lifetime (k/sec): (4397508/147)
         IV size: 8 bytes
         replay detection support: Y
         Status: ACTIVE
      outbound ah sas:
       spi: 0xA83E05B5(2822636981)
         transform: ah-sha-hmac ,
         in use settings ={Tunnel, }
         conn id: 94, flow_id: SW:94, crypto map: Tunnel0-head-0
         sa timing: remaining key lifetime (k/sec): (4397508/147)
         replay detection support: Y
         Status: ACTIVE
      outbound pcp sas:

Sample Output from the show crypto isakmp peer Command

The following sample output shows peer descriptions on an IPv6 router:

Router# show crypto isakmp peer detail
Peer: 2001:DB8:0:1::1 Port: 500 Local: 2001:DB8:0:2::1
Phase1 id: 2001:DB8:0:1::1
flags: 
NAS Port: 0 (Normal)
IKE SAs: 1 IPsec SA bundles: 1
last_locker: 0x141A188, last_last_locker: 0x0
last_unlocker: 0x0, last_last_unlocker: 0x0

Sample Output from the show crypto isakmp profile Command

The following sample output shows the ISAKMP profiles that are defined on an IPv6 router:

Router# show crypto isakmp profile
ISAKMP PROFILE tom
Identities matched are:
ipv6-address 2001:DB8:0:1::1/32 
Certificate maps matched are:
Identity presented is: ipv6-address fqdn
keyring(s): <none>
trustpoint(s): <all>

Sample Output from the show crypto isakmp sa Command

The following sample output shows the SAs of an active IPv6 device. The IPv4 device is inactive.

Router# show crypto isakmp sa detail

Codes: C - IKE configuration mode, D - Dead Peer Detection

        K - Keepalives, N - NAT-traversal

        X - IKE Extended Authentication

        psk - Preshared key, rsig - RSA signature

        renc - RSA encryption

IPv4 Crypto ISAKMP SA

C-id  Local           Remote          I-VRF    Status Encr Hash Auth DH 

Lifetime Cap.

IPv6 Crypto ISAKMP SA

  dst: 3FFE:2002::A8BB:CCFF:FE01:2C02

  src: 3FFE:2002::A8BB:CCFF:FE01:9002

  conn-id: 1001  I-VRF:          Status: ACTIVE Encr: des  Hash: sha  Auth: 

psk

  DH: 1  Lifetime: 23:45:00 Cap: D    Engine-id:Conn-id = SW:1

  dst: 3FFE:2002::A8BB:CCFF:FE01:2C02

  src: 3FFE:2002::A8BB:CCFF:FE01:9002

  conn-id: 1002  I-VRF:          Status: ACTIVE Encr: des  Hash: sha  Auth: psk

  DH: 1  Lifetime: 23:45:01 Cap: D    Engine-id:Conn-id = SW:2

Sample Output from the show crypto map Command

The following sample output shows the dynamically generated crypto maps of an active IPv6 device:

Router# show crypto map
 
Crypto Map "Tunnel1-head-0" 65536 ipsec-isakmp
        Profile name: profile0
        Security association lifetime: 4608000 kilobytes/300 seconds
        PFS (Y/N): N
        Transform sets={
                ts,
        }
Crypto Map "Tunnel1-head-0" 65537
        Map is a PROFILE INSTANCE.
        Peer = 2001:1::2
IPv6 access list Tunnel1-head-0-ACL (crypto)
    permit ipv6 any any (61445999 matches) sequence 1
        Current peer: 2001:1::2
        Security association lifetime: 4608000 kilobytes/300 seconds
        PFS (Y/N): N
        Transform sets={
          ts,
        }
        Interfaces using crypto map Tunnel1-head-0:
        Tunnel1

Sample Output from the show crypto session Command

The following output from the show crypto session command provides details on currently active crypto sessions:

Router# show crypto session detail
Crypto session current status
Code: C - IKE Configuration mode, D - Dead Peer Detection K - Keepalives, N - NAT-traversal, X - IKE Extended Authentication
Interface: Tunnel1
Session status: UP-ACTIVE
Peer: 2001:1::1 port 500 fvrf: (none) ivrf: (none)
       Phase1_id: 2001:1::1
       Desc: (none)
   IKE SA: local 2001:1::2/500
           remote 2001:1::1/500 Active
           Capabilities:(none) connid:14001 lifetime:00:04:32
   IPSEC FLOW: permit ipv6 ::/0 ::/0
         Active SAs: 4, origin: crypto map
         Inbound:  #pkts dec'ed 42641 drop 0 life (KB/Sec) 4534375/72
         Outbound: #pkts enc'ed 6734980 drop 0 life (KB/Sec) 2392402/72