When using IPv6, why does the message "Neighbour table overflow" in /var/log/messages appear frequently when using TPROXY?

Issue

• When using TPROXY, a transparent proxy tool and IPv6 in conjunction there are multiple references of this kernel message in /var/log/messages:

2012-11-01T11:52:26.991773-07:00 system kernel: [161634.116941] Neighbour table overflow.
2012-11-01T11:52:31.991635-07:00 system kernel: [161639.109391] __ratelimit: 67475 callbacks suppressed
2012-11-01T11:52:31.991664-07:00 system kernel: [161639.109395] Neighbour table overflow.
2012-11-01T11:52:31.991667-07:00 system kernel: [161639.109435] Neighbour table overflow.

• Furthermore, when these messages appear poor network performance occurs.