Issue:
#ping xxxx
connect: No buffer space available

#dmesg
Neighbour table overflow messages.

Solution:
To fix this, I had to increase the ARP table space. To do this permanently:
Edit /etc/sysctl.conf and add the following lines:
net.ipv4.neigh.default.gc_thresh1 = 1280
net.ipv4.neigh.default.gc_thresh2 = 5120
net.ipv4.neigh.default.gc_thresh3 = 10240

# sysctl -p

For a temporary fix:
echo 1280 > /proc/sys/net/ipv4/neigh/default/gc_thresh1
echo 5120 > /proc/sys/net/ipv4/neigh/default/gc_thresh2
echo 10240 > /proc/sys/net/ipv4/neigh/default/gc_thresh3

References:
http://mysysadminnotes.blogspot.com/2010/12/no-bufferspace-available-error.html
http://www.packetfence.org/support/faqs/article/i-am-getting-neighbour-table-overflow-errors-what-should-i-do.html?no_cache=1&cHash=983fe6823edd14a20fb0d66303d16b5f