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Problems with LAN to LAN VPN with NAT traversal



Article ID: KB5236 KB Last Updated: 24 Aug 2010Version: 3.0

NAT traversal VPN tunnel
Main mode
VPN using Preshared secret
No IKE cookie shown on the NetScreen with no NAT device in front of it
IKE phase 1 not establishing
NAT traversal VPN not working
VPN not working
Cannot get LAN to LAN VPN to work with NAT

When using preshared secret with NAT traversal, both gateways must be configured with Aggressive mode.'  Main mode is only supported with certificates.'  Change both gateways to aggressive mode.'  The following is a sample of a successful NAT traversal Phase 1 negotiation:
From the NetScreen not NAT'd, get ike cookie:
522f/6,> PRESHR/grp2/AES/SHA, xchg(4) usr(d-1/u-1)
resent-tmr 0 lifetime 28800 lt-recv 28800 nxt_rekey 28708 cert-expire 0
'  initiator 0, in-out 0, err cnt 0, send dir 1, cond 0
nat-traversal map:
'  sa index 0.
'  keepalive frequency 5 sec
'  nat-t udp checksum enabled
'  local pri ip'
'  local pri ike port 500
'  local pub ip
'  local pub ike port 0
'  remote pri ip'
'  remote pri ike port 500
'  remote pub ip'
'  remote pub ike port 23728
'  internal ip
'  internal port 0
'  natt proto 17
ike heartbeat' ' ' ' ' ' ' ' ' ' ' ' '  : disabled
ike heartbeat last rcv time: 0
ike heartbeat last snd time: 0 is the external interface of the NAT device in front of the NetScreen.' is the untrust interface of the NetScreen (no NAT)' is the untrust interface of the NetScreen behind the NAT device

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