I wanted to mention a new AIX feature, available with AIX 7.1 TL3 (and 6.1 TL9) called the ‘AIX Virtual Ethernet Link Status’ capability. Previous implementations of Virtual Ethernet do not have the ability to detect loss of network connectivity.

For example, if the VIOS SEA is unavailable and VIO clients are unable to communicate with external systems on the network, the Virtual Ethernet adapter would always remain “connected” to the network via the Hypervisors virtual switch. However, in reality, the VIO client was cut off from the external network.

This could lead to a few undesirable problems, such as, a) needing to provide an IP address to ping for Etherchannel (or NIB) configurations to force a failover during a network incident, lacking the ability to auto fail-back afterwards, b) unable to determine total device failure in the VIOS and c) PowerHA fail-over capability was somewhat reduced as it was unable to monitor the external network “reach-ability”.

The AIX VEA Link Status feature provides a way to overcome the previous limitations. The new VEA device will periodically poll the VIOS/SEA using L2 packets (LLDP format). The VIOS will respond with its physical device link status. If the VIOS is down, the VIO client times out and sets the uplink status to down.

To enable this new feature you’ll need your VIO clients to run either AIX 7.1 TL3 or AIX 6.1 TL9. Your VIOS will need to be running v2.2.3.0 at a minimum (recommend 2.2.3.1). There’s no special configuration required on the VIOS/SEA to support this feature. On the VIO client, you’ll find two new device attributes that you can configure/tune. These attributes are:

poll_uplink (yes, no)
poll_uplink_int (100ms – 5000ms)

Here’s some output from the lsattr and chdev commands on my test AIX 7.1 TL3 partition that show these new attributes.

# oslevel -s

7100-03-01-1341

# lsattr -El ent0 | grep poll

poll_uplink no Enable Uplink Polling True

poll_uplink_int 1000 Time interval for Uplink Polling True

# lsattr -El ent0 -a poll_uplink

poll_uplink no Enable Uplink Polling True

# lsattr -Rl ent0 -a poll_uplink

yes

# lsattr -Rl ent0 -a poll_uplink_int

100...5000 (+10)

# ifconfig en0 down detach

# chdev -l ent0 -a poll_uplink=yes

ent0 changed

# chdev -l en0 -a state=up

en0 changed

# mkdev -l inet0

inet0 Available

# ifconfig en0

en0: flags=1e080863,480<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),CHAIN>

inet 10.1.5.9 netmask 0xffffff00 broadcast 10.1.5.255

tcp_sendspace 262144 tcp_recvspace 262144 rfc1323 1

Right now, the entstat command doesn’t report the bridge (VIOS/SEA) status. However, this APAR (IV55505) indicates that this feature is coming.

http://www-01.ibm.com/support/docview.wss?uid=isg1IV55505

This feature is still considered “new” but I’m very interested to see how this will integrate with PowerHA in the future. Perhaps the use of “Single Adapter” configurations with PowerHA will become more robust (allowing PowerHA to track and respond to network events)...…and possibly more prevalent. You can find more information on this feature here:

http://www-01.ibm.com/support/docview.wss?uid=isg1IV41103