PI84915: PACKET FORWARDING PROBLEM ON AIX

Fixes are available

APAR status

Closed as program error.

Error description

The problem corrected applies to AIX users only. Noticable
problems include the cluster being nonresponsive (executor
report does not show any incoming packets), pings fail, high
availability partners both active or system crash.

Local fix

Problem summary

****************************************************************
* USERS AFFECTED:  IBM WebSphere Application Server Load       *
*                  Balancer for IPv4 and IPv6 users on AIX     *
****************************************************************
* PROBLEM DESCRIPTION: Packet forwarding does not work,        *
*                      pings to cluster fail, executor         *
*                      reports shows no incoming               *
*                      packets...more.                         *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
The Load Balancer for IPv4 and IPv6 on AIX utilitizes the
ns_tap socket filter to process ARP traffic. When this
resource is not available many of the load balancer functions
do not operate correctly.
We have observed the following failures:
-- system crash starting the executor with os_addiface on
the stack.
-- Both highavailability partner operate in an "active" state
-- Pings to the cluster and return addresses fail
-- Executor report shows no packets received for any cluster
-- Users find it necessary to alias the cluster on the
ethernet interface to get LB to operate.
Prior levels of the load balancer did not provide a clear
indication of the failure to obtain the ns_tap resource. This
code change adds a message to allow users to see if they
are encountering this issue as well as the ability to disable
use of the ns_tap filter if desired.

Problem conclusion

After applying this fix and loading your configuration,
you can check to see if there are any errors with the load
balancer obtain the ns_tap filter by executing the following
command from the /opt/IBM/WebSphere/Edge/ULB/servers/bin
directory :
./lb_kext -l
View the ibmulb_log1 file which is created for any errors
related to ns_add_filter and take any recommended actions.

The ns_tap filter is used by the network trace facility
(iptrace and tcpdump) so you can not obtain a network trace
while load balancer is running and load balancers arp
functions will not operate when a network trace is started
before the executor prior to this code change. You can modify
LB not to use the ns_tap resource by changing LB_PROMISCOUS
from "0" to "1" in
/opt/IBM/WebSphere/ULB/servers/bin/lbexecutor.AIX. You must
restart the executor for this change to take effect.

If LB_PROMISCOUS is set to "1" or the ns_tap resource is not
working, you will need to alias all clusters using go scripts
(in using the highavailability feature) or the "executor
configure" command. Sample go scripts are provided in the
/opt/IBM/WebSphere/Edge/ULB/servers/samples directory. After
they have been configured for the desired clusters, they need
to be moved to the /opt/IBM/WebSphere/Edge/ULB/servers/bin
directory and execute permission set on the scripts.

The "executor configure" command has the following syntax:
dscontrol executor configure <cluster> <interface> <prefix>
The interface and prefix are optional and the NFA interface
and prefix are used if they are not provided.

This change is included in :
   8.5.5.13
   9.0.0.6

Temporary fix

Comments

APAR Information

APAR number
PI84915
Reported component name
WS EDGE LB IPV4
Reported component ID
5724H8812
Reported release
900
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2017-07-24
Closed date
2017-08-20
Last modified date
2020-06-30

APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:

Fix information

Fixed component name
WS EDGE LB IPV4
Fixed component ID
5724H8812

Applicable component levels

R850 PSY
UP
R900 PSY
UP

[{"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"Product":{"code":"SSEQTP","label":"WebSphere Application Server"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"900","Line of Business":{"code":"LOB45","label":"Automation"}}]

Document Information

Modified date:
04 May 2022

Tips

PI84915: PACKET FORWARDING PROBLEM ON AIX

Fixes are available

Subscribe

APAR status

Closed as program error.

Error description

Local fix

Problem summary

Problem conclusion

Temporary fix

Comments

APAR Information

APAR number

Reported component name

Reported component ID

Reported release

Status

PE

HIPER

Special Attention

Submitted date

Closed date

Last modified date

APAR is sysrouted FROM one or more of the following:

APAR is sysrouted TO one or more of the following:

Fix information

Fixed component name

Fixed component ID

Applicable component levels

R850 PSY

R900 PSY

Document Information

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