To find the closest and/or fastest CentOS mirror, a function which is sadly lacking from CentOS (at least as of v6), this is what I just hacked together. Documenting it here for posterity. (If you wanted to sort by RTT instead of hopcount, you could either reverse the order of i & t in the END block of the awk script, or figure out sort(1)'s ridiculous -k option.)

#!/bin/sh printf 'Hops\tPing\tHost\n' for h in $( lynx -listonly -nonumbers -dump http://isoredirect.centos.org/centos/6/isos/x86_64/ | egrep '^https?://' | sed -e 's#^https*://([^/]*)/.*$#\1#' ); do mtr -c 1 -r $h | awk -v h=$h 'BEGIN {i=0;t=0} /^ *[0-9]*./ {i++; t=$5} END {print i,t,h}' & done | sort -n | head -10 wait