How to guide for checking and testing APA configurations in HPUX. Auto Port Aggregation is used for NIC redundancy which is similar to NIC teaming in Linux.
APA stands for Auto Port aggregation. It is software i.e. operating system level configuration which offers NIC (Network Interface Card also referred as LAN card) redundancy. Under APA in HPUX, two NICs are configured together as a single virtual card at OS level. For OS, its a single NIC its talking to. But physically there are 2 NIC handling requests on this virtual card. In occasion of hardware failure of any one physical card, other physical card service OS (through virtual card) without hampering operations.
Complete guide : How to configure APA in HPUX
Normally, physical NIC are numbered as lan0, lan1, lan2 and so on. APA in HPUX terms new virtual cards as lan900, lan901 and so on. Current list of lan cards on system can be obtained using below command :
# ioscan -fnClan Class I H/W Path Driver S/W State H/W Type Description ===================================================================== lan 0 2/0/0/1/0 igelan CLAIMED INTERFACE HP PCI-X 1000Base-T Built-in lan 1 2/0/4/1/0 iether CLAIMED INTERFACE HP A7012-60601 PCI/PCI-X 1000Base-T Dual-port Adapter lan 2 2/0/4/1/1 iether CLAIMED INTERFACE HP A7012-60601 PCI/PCI-X 1000Base-T Dual-port Adapter lan 3 2/0/6/1/0 iether CLAIMED INTERFACE HP A7012-60601 PCI/PCI-X 1000Base-T Dual-port Adapter
In above output you can see, second column which show lan number. So we have 4 lan cards numbering lan0 to lan3 here. But in this output, you wont be able to see APA interfaces i.e. virtual NIC.
For checking APA interfaces you need to use lanscan command.
# lanscan -q 2 3 900 901 0 1 902 903 904
Here you can see lan0 and lan 1 combined together forms lan901 interface which is APA card. Since those are used in APA, you dont see them as seprate entry like lan2 and lan3. This way you can trace physical NIC and their respective virtual or APA interfaces.
To test APA means to check if your network connectivity via APA interface is uninterrupted in case of one of the physical NIC failure.
You can test this by removing one of the NIC physically from system board. But this is not recommended since abruptly removing card from board also invites un-forseen hardware issues. So, to test APA we have to emulate NIC failure or shuts NIC down without touching hardware.
This can be achieved by resetting NIC using lanadmin command. Resetting NIC, makes card unavailable/un-operational for few seconds. This time is enough for us to test APA in HPUX.
Complete test can be carried out in below order:
- Identify IP defined on lan901 (our APA interface)
- Keep continuous ping on for this IP
- Reset lan0
- Observe ping
- Once lan0 comes back up reset lan1
- Observe ping
- Make sure both lan0 and lan1 are back online.
To reset lan you can use below command :
# lanadmin -r 0
To check if lan being reset is online or offline in APA
# lanscan -q 2 3 900 901 1 <<<< missing 0 means lan0 is offline
Repeat above command till lan901 shows 0 and 1 both interfaces.
During this test, you may observe one or two ping loss. This is due to APA shifting loads to only available interface. This ping loss wont hamper operating environment because its far less than timeout values defined in software/tools used on OS. Hence redundancy is maintained in case of NIC failure.
Above test will fail i.e. you will completely lost ping to IP in below scenarios :
- Your APA configuration is erroneous
- One or both lan interfaces are not configured properly at network level (vlan configurations)