9.4.5. Troubleshooting with ikesnoop
Step 5. Client Sends Identification
The initiator sends the identification which is normally an IP address or the Subject Alternative
Name if certificates are used.
IkeSnoop: Received IKE packet from 192.168.0.10:500 Exchange type :
Identity Protection (main mode) ISAKMP Version : 1.0
Flags
Cookies
Message ID
Packet length
# payloads
Payloads:
ID (Identification)
Payload data length : 8 bytes
ID : ipv4(any:0,[0..3]=192.168.0.10)
HASH (Hash)
Payload data length : 16 bytes
N (Notification)
Payload data length : 8 bytes
Protocol ID
Notification : Initial contact
Explanation of Above Values
Flags: E means encryption (it is the only flag used).
ID: Identification of the client
The Notification field is given as Initial Contact to indicate this is not a re-key.
Step 6. Server ID Response
The server now responds with its own ID.
IkeSnoop: Sending IKE packet to 192.168.0.10:500 Exchange type :
Identity Protection (main mode) ISAKMP Version : 1.0
Flags
Cookies
Message ID
Packet length
# payloads
Payloads:
ID (Identification)
Payload data length : 8 bytes
ID : ipv4(any:0,[0..3]=192.168.10.20)
HASH (Hash)
Payload data length : 16 bytes
Step 7. Client Sends a List of Supported IPsec Algorithms
Now the client sends the list of supported IPsec algorithms to the server. It will also contain the
proposed host/networks that are allowed in the tunnel.
IkeSnoop: Received IKE packet from 192.168.0.10:500 Exchange type :
: E (encryption)
: 0x6098238b67d97ea6 -> 0x5e347cb76e95a
: 0x00000000
: 72 bytes
: 3
: ISAKMP
: E (encryption)
: 0x6098238b67d97ea6 -> 0x5e347cb76e95a
: 0x00000000
: 60 bytes
: 2
357
Chapter 9. VPN