/etc/ppp/ip-up.d/fixroute.pl

#!/usr/bin/perl

my $TT  = `ip route |grep ppp | grep -v default`;
my $DEF = `ip route |grep default| grep -v ppp | gawk '{print \$3}'`;
my $LS  = `ip route |grep ppp| gawk '{print \$1}'`;
my $PPP = `ifconfig -s |grep ppp|gawk '{print \$1}'`;

chomp $TT; chomp $DEF; chomp $LS; chomp $PPP;


print "TT: $TT, DEF: $DEF, LS: $LS, PPP: $PPP\n---------\n";

for (split(/\n/, $TT)) {
   doc("ip route del $_");
}

for (split(/\n/, $DEF)) {
   doc("ip r d default via \"$_\" dev lan");
   $DEF = $_; # Только 1 DEF интересен
}

doc("ip route add $LS via $DEF") if $DEF;
doc("ip route add default dev $PPP") if $DEF;

sub doc {
   my $c = shift;
   print "do: $c\n";
   print `$c`;
}