It may be useful, if you're using dn42 on linux with suitable named interfaces

dn42_countroute

#!/usr/bin/env sh
echo '    IPv4'
ip r | cut -d' ' -f 5 | grep dn42 |perl -MList::Util=sum -E 'my %cnt; $fmt = "%3d %s\n"; while (<>) { chomp; $cnt{$_}++ }; for my $k (reverse sort { $cnt{$a} <=> $cnt{$b} || -($a cmp $b)  } keys %cnt) { printf($fmt, $cnt{$k}, $k) } printf($fmt, sum(values %cnt), "total"); printf($fmt, scalar keys %cnt, "peerings")'
echo
echo '    IPv6'
ip -6 r | cut -d' ' -f 5 | grep dn42 |perl -MList::Util=sum -E 'my %cnt; $fmt = "%3d %s\n"; while (<>) { chomp; $cnt{$_}++ }; for my $k (reverse sort { $cnt{$a} <=> $cnt{$b} || -($a cmp $b)  } keys %cnt) { printf($fmt, $cnt{$k}, $k) } printf($fmt, sum(values %cnt), "total"); printf($fmt, scalar keys %cnt, "peerings")'

Here is an counterpart for someone like me who is using FreeBSD and can't really use named interfaces:

#!/usr/bin/env sh
netstat -anr | egrep '(gre|tun)' | awk '{print $2}' | egrep -v '(\#|\%)' | egrep '^[0-9]*[:\.]+' | perl -MList::Util=sum -E 'my %cnt; $fmt = "%3d %s\n"; while (<>) { chomp; $cnt{$_}++ }; for my $k (reverse sort { $cnt{$a} <=> $cnt{$b} } keys %cnt) { printf($fmt, $cnt{$k}, $k) } printf($fmt, sum(values %cnt), "total"); printf($fmt, scalar keys %cnt, "peerings")'