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[Dave Liebreich <dliebreich@xxxxxxxxxxxxxxx>]

Public bug reported:

in an AWS environment managed by BOSH, we saw tcp connectivity problems
between pairs of VMs.

VM A and VM B are up, running ubuntu 14.04-based images, and in the same
vpc subnet.

VM B is terminated, and another VM is created that uses the IP address
from VM B

The new VM tries to make a tcp connection to VM A. In some cases, the
connection fails.

Investigation reveals that VM A has the old MAC address in its neighbor
list. In some cases, running arp -d <IP Address> on VM A "fixes the
problem". Also in some cases, running arping in gratuitous arp mode on
the new VM also fixes the problem.

The problem does not occur if VM A is running an ubuntu 10.04-based
image.

The problem seems to occur only on machines with lots of tcp connection
traffic between them.

'arp -d' and arping on the new VM do not seem to "fix" the problem if
there are processes on the VMs that are trying to create new TCP
connections.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1331150

Title:
  arp fails to update, 3.13.0-{24,29}

Status in “linux” package in Ubuntu:
  New

Bug description:
  in an AWS environment managed by BOSH, we saw tcp connectivity
  problems between pairs of VMs.

  VM A and VM B are up, running ubuntu 14.04-based images, and in the
  same vpc subnet.

  VM B is terminated, and another VM is created that uses the IP address
  from VM B

  The new VM tries to make a tcp connection to VM A. In some cases, the
  connection fails.

  Investigation reveals that VM A has the old MAC address in its
  neighbor list. In some cases, running arp -d <IP Address> on VM A
  "fixes the problem". Also in some cases, running arping in gratuitous
  arp mode on the new VM also fixes the problem.

  The problem does not occur if VM A is running an ubuntu 10.04-based
  image.

  The problem seems to occur only on machines with lots of tcp
  connection traffic between them.

  'arp -d' and arping on the new VM do not seem to "fix" the problem if
  there are processes on the VMs that are trying to create new TCP
  connections.

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