Bug ID 453959: UDP profile improvement for flexible TTL handling

Last Modified: Sep 13, 2023

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

Known Affected Versions:
11.5.1 HF1, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4, 11.5.1 HF5, 11.5.1 HF6, 11.5.1 HF7, 11.5.1 HF8, 11.5.1 HF9, 11.5.1 HF10, 11.5.1 HF11, 11.5.2 HF1, 11.5.3 HF1, 11.5.3 HF2, 11.5.4 HF1, 11.5.4 HF2, 11.5.4 HF3, 11.5.4 HF4, 11.5.1, 11.5.2, 11.5.3, 11.5.4, 11.5.5, 11.5.6, 11.5.7, 11.5.8, 11.5.9, 11.5.10, 12.1.0 HF1, 12.1.0 HF2, 12.1.1 HF1, 12.1.1 HF2, 12.1.2 HF1, 12.1.2 HF2

Fixed In:
12.0.0, 11.6.0 HF4

Opened: Mar 25, 2014

Severity: 3-Major

Symptoms

The UDP virtual used by PEM treats TTL differently than the standard UDP forwarding virtual. The standard UDP forwarding virtual decrements TTL whereas the PEM UDP virtual reinitializes TTL to 255. In the event that there is a routing loop in the network which traverses a BIG-IP running PEM, this behavior would prevent TTL from expiring and thus exacerbate the effects of the loop.

Impact

A PEM virtual doesn't have the flexibility to decrement the TTL value on PEM UDP listener because it is always reset to 255.

Conditions

This inconsistency of TTL handling between standard LTM virtual and PEM virtual (with PEM enabled).

Workaround

There is no workaround for this.

Fix Information

With this improvement, you will have the flexibility to define the TTL handling behavior (decrease by 1 vs. resetting to 255). This can be archived by change db variable(tmm.udp.ttl.mode) on 11.6.0 hotfix: tmsh modify sys db tmm.udp.ttl.mode value "decrement"

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips