Bug ID 541569: IPsec NAT-T (IKEv1) not working properly

Last Modified: Apr 28, 2025

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:
11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5, 11.6.0 HF6, 11.6.0 HF7, 11.6.0 HF8, 12.0.0, 12.0.0 HF1, 12.0.0 HF2

Fixed In:
12.1.0, 12.0.0 HF3, 11.6.1

Opened: Aug 24, 2015

Severity: 3-Major

Related Article: K59519340

Symptoms

The incorrect source port is chosen for the IPsec/IKE NAT-T UDP encapsulated traffic. When IKE decides to float port when NAT device is detected, it should use port 4500 for both its source port and destination port.

Impact

When NAT-T is enabled, IPsec tunnel cannot be established.

Conditions

NAT traversal is enabled on the IKE Peer configuration object and NAT device is detected during IKE negotiation.

Workaround

None.

Fix Information

Now, when NAT-T is enabled, IPsec tunnel can be established as expected.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips