Já que você está usando o Debian Linux, você pode fazê-lo bem simples. Você pode usar esse script para uma repartição "justa" na largura de banda:
#Put here your Internet-interface instead of eth1
ext_iface=eth1
eiface_addr=192.169.158.150
###############Remove shaper rules###############################3
iptables -t mangle --flush
tc qdisc del dev $ext_iface root 2> /dev/null > /dev/null
iptables -t mangle -D POSTROUTING -o $ext_iface -j shape-in 2> /dev/null > /dev/null
iptables -t mangle -F shape-in 2> /dev/null > /dev/null
iptables -t mangle -X shape-in 2> /dev/null > /dev/null
##############Adding shaper rules###################################
tc qdisc add dev $ext_iface root handle 1:0 htb default 10
tc class add dev $ext_iface parent 1:0 classid 1:1 htb rate 100mbit ceil 100mbit
tc class add dev $ext_iface parent 1:1 classid 1:5 htb rate 100mbit ceil 100mbit prio 0
tc class add dev $ext_iface parent 1:1 classid 1:10 htb rate 48mbit ceil 48mbit prio 0
tc qdisc add dev $ext_iface parent 1:5 handle 5: pfifo limit 5
tc qdisc add dev $ext_iface parent 1:10 handle 10: pfifo limit 10
iptables -t mangle -N shape-in
iptables -t mangle -I POSTROUTING -o $ext_iface -j shape-in
#Priority for pings
iptables -t mangle -A shape-in -p icmp -j MARK --set-mark 5
#Priority for Server Access
iptables -t mangle -A shape-in -s $eiface_addr -j MARK --set-mark 5
#Othet packets (user\'s internet traffic)
iptables -t mangle -A shape-in -m mark --mark 0 -j MARK --set-mark 10
tc filter add dev $ext_iface parent 1:0 prio 0 protocol ip handle 5 fw flowid 1:5
tc filter add dev $ext_iface parent 1:0 prio 1 protocol ip handle 10 fw flowid 1:10
Observe que os usuários receberão 48 / n canal e restam dois Mbs para uma reserva.