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Monday, 26 November 2012

NPIV: N-Port ID Virtualization

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What is beacon probing?


Purpose

This article provides information on beacon probing.

Resolution

Beacon probing is a network failover detection mechanism that sends out and listens for beacon probes on all NICs in the team and uses this information along with link status to determine link failure. Beacon probing detects failures, such as cable pulls and physical switch power failures on the immediate physical switch and also on the downstream switches.
How does beacon probing work?
ESX/ESXi periodically broadcasts beacon packets from all uplinks in a team. The physical switch is expected to forward all packets to other ports on the same broadcast domain. Therefore, a team member is expected to see beacon packets from other team members. If an uplink fails to receive three consecutive beacon packets, it is marked as bad. The failure can be due to the immediate link or a downstream link.

Beaconing is most useful with three or more uplinks in a team because ESX/ESXi can detect failures of a single uplink. When there are only two NICs in service and one of them loses connectivity, it is unclear which NIC needs to be taken out of service because both do not receive beacons and as a result all packets sent to both uplinks. Using at least three NICs in such a team allows for n-2 failures where n is the number of NICs in the team before reaching an ambiguous situation. These uplink NICs should be in an active/active or active/standby configuration because the NICs in an Unused state do not participate in the beacon probing process.

When should you enable beacon probing?
You must enable beacon probing when downstream link failures may impact availability and there is no Link State Tracking on the physical switch.
Source:-
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1005577

Troubleshooting IP-Hash outbound NIC selection


Symptoms

If you have configured a NIC team for your VMkernel traffic using 2 physical uplinks, EtherChannel, and 2 storage target IP's, you may experience the following symptoms if you are using IP-Hash for load balancing: 
  • The vSwitch's traffic is not balanced across uplink adapters. 
  • All traffic is transmitted out of a single uplink adapter.

Resolution

This issue may occur if the calculated hash returns the same result based on the source IP and both destination IP's.
 
To resolve this issue, use this example to manually calculate the IP-Hash with the IP's you are using to help you choose 2 target IP's that utilize both uplinks on the vSwitch. 

To convert the NFS IP addresses to Hex:
  1. Use any online IP Hex Converter tool to convert the IP addresses to Hex.

    This is an example we used a vSwitch with 2 uplinks, EtherChannel and IP-Hash:
     
    Links = 2 (0 and 1)
    VMKnic 10.0.0.10 = 0xa00000a
    NFS1 10.0.0.20 = 0xa000014
    NFS2 10.0.0.22 = 0xa000016
  2. Use the following IP-Hash formula to calculate the outbound uplink:

    VMKnic > NFS1 (0xa00000a Xor 0xa000014 =1E) % 2= 0
    VMKnic > NFS2 (0xa00000a Xor 0xa000016 =1C) % 2= 0
    1. On any scientific calculator, select Hex and Qword.
    2. Enter the VMKnic IP in HEX format (a00000a) and click Xor.
    3. Enter NFS1 IP in HEX format (a000014) and click =.
    4. Press Mod, press 2 for the number of uplinks, then click =. The result is 0.
    5. Repeat steps a-e, using the NFS2 IP (a000016) in step c. The result is also 0.

      IP-Hash chooses the first uplink in the team because they both have result of 0.
To ensure that IP-Hash balances outbound traffic:
  1. Change the IP for NFS2 from 10.0.0.22 to 10.0.0.21.
  2. Use any online IP Hex Converter tool to convert the IP addresses to Hex.

    For example:
    Links = 2 (0 and 1)
    VMknic 10.0.0.10 = 0xa00000a
    NFS1 10.0.0.20 = 0xa000014
    NFS2 10.0.0.21 = 0xa000015
  3. Use the following IP-Hash formula to calculate the outbound uplink:
    VMKnic > NFS2 (0xa00000a Xor 0xa000015 =1F) % 2= 1
    1. On any scientific calculator, select Hex and Qword.
    2. Select Hex and Qword.
    3. Enter the VMKnic IP in HEX format (a00000a) and click Xor.
    4. Enter NFS2 IP in HEX format (a000015) and click =.
    5. Press Mod, press 2 for the number of uplinks, then click =. The result is 1.

      Now the IP-Hash algorithm returns a different result. IP-Hash now balances the outbound traffic across both vSwitch uplinks.
Source:-
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1007371