Bug ID 541156: Network Access clients experience delays when resolving a host

Last Modified: Apr 19, 2021

Bug Tracker

Affected Product:  See more info
BIG-IP APM(all modules)

Known Affected Versions:
11.4.1, 11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 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, 11.5.10, 11.5.2, 11.5.2 HF1, 11.5.3, 11.5.3 HF1, 11.5.3 HF2, 11.5.4, 11.5.4 HF1, 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, 11.6.1, 12.0.0, 12.0.0 HF1, 12.0.0 HF2, 12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3,,,,,,,, 12.1.4,, 12.1.5,,,, 12.1.6

Fixed In:
13.0.0, 12.0.0 HF3, 11.6.1 HF1, 11.5.4 HF2

Opened: Aug 20, 2015
Severity: 4-Minor


The DNS Relay proxy for Network Access clients operating in split-tunnel mode intercepts a client's DNS request for a non-matching host and will forward it to the client's local DNS server. If the client contains multiple NICs, one containing a down or invalid DNS server, this could cause a delay in resolving the host.


Clients will experience unusual delays (10+ seconds) when resolving hosts.


Network Access with the DNS Relay Proxy configured A client machine has multiple NICs One of the NICs has an invalid or down DNS server configured Client attempts to resolve a host not matching the Network Access policy


Clients can check their system setup and remove the affected interfaces that contain an invalid DNS server (virtual machine network adapters are becoming increasingly common and can exhibit this), or they can ensure that they are mapped only to valid DNS servers that can resolve the host.

Fix Information

The DNS Relay proxy will now avoid sending DNS requests to down DNS servers for DNS requests that do not match the Network Access policy while Network Access is connected.

Behavior Change