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Max Concurrent Connections in a IPV6 VM RRS feed

  • Question

  • If i am running a Ubuntu VM in Azure ( D2v2) i am able to make only 1024 concurrent TCP/IP connections on IPV6 while on IPV4

    i am able to achieve more that 30,000 connections.

    Is this a limitation on the VM or OS or Azure.

    Thanks

    Ameen


    Ameen

    Wednesday, August 14, 2019 5:19 PM

All replies

  • Hi, 

    How are you performing those test?

    When you say I am able to achieve more than 30,000 connections, is it with IPv4 address?

    Also, does your setup includes the LB where you have public IP address and have 2 ipconfigs in your NIC, one with IPv4 and another with IPv6?

    Regards, 

    Msrini

    Friday, August 16, 2019 6:11 AM
    Moderator
  • There is a small JAVA application built which will be creating multiple TCP/IP  connections.

    Yes 30,000 connections is via IPV4.

    Yes, it has a LB with public IP address and 2 NICs with IPV4 and IPV6. 

    THanks

    Ameen


    Ameen

    Friday, August 16, 2019 6:38 AM
  • Are you using Basic or Standard Load balancer?

    The 1024 connection which you have mentioned, is it the outbound connection from the VM?

    Regards, 

    Msrini

    Friday, August 16, 2019 7:18 AM
    Moderator
  • Yes to both.

    Thanks

    Ameen


    Ameen

    Friday, August 16, 2019 10:57 AM
  • Hi, 

    1024 is the number of outbound SNAT ports that are allocated to instances behind a load balancer, but that could translate into much higher number of outbound flows, if the destinations are different, or at least 1024 connections to the same destination IP Address. There is not a specific limitation as such with IPv6 address. 

    When you tried outbound connectivity from the VM, is the destination same?

    After 1024 connections, are you getting timeout error?

    Regards, 

    Msrini

    Friday, August 16, 2019 5:44 PM
    Moderator
  • Hi, 

    Do you have any update on this issue?

    Regards, 

    Msrini

    Monday, August 19, 2019 11:38 AM
    Moderator
  • 1. Each VM which is making outbound connections is to different IPV6 destinations and not the same one.

    2. There is no specific error, but the connections from the VM via Load Balancer stops.

    3. So is this a Limitation from the Standard load balancer, so in that case what is the workaround.

    Thanks

    Ameen


    Ameen

    Monday, August 19, 2019 3:24 PM
  • Yes, it is a limitation that you can only make 1024 concurrent calls outbound from a VM which is behind the Standard Load balancer. There are no workaround at this moment. 

    Regards, 

    Msrini

    Monday, August 19, 2019 3:40 PM
    Moderator
  • Hi, 

    Just checking in if you have had a chance to see the previous response. If this answers your query, do click “Mark as Answer” and Up-Vote for the same.

    Regards, 

    Msrini

    Friday, August 23, 2019 6:42 AM
    Moderator