diff --git a/private.go b/private.go
new file mode 100644
index 0000000..e048dd5
--- /dev/null
+++ b/private.go
@@ -0,0 +1,73 @@
+package manet
+
+import (
+	"net"
+
+	ma "github.com/multiformats/go-multiaddr"
+)
+
+// Private4 and Private6 are well-known private networks
+// These are exported to allow overriding for testing
+var Private4, Private6 []*net.IPNet
+var privateCIDR4 = []string{
+	// localhost
+	"127.0.0.0/8",
+	// private networks
+	"10.0.0.0/8",
+	"100.64.0.0/10",
+	"172.16.0.0/12",
+	"192.168.0.0/16",
+	// link local
+	"169.254.0.0/16",
+}
+var privateCIDR6 = []string{
+	// localhost
+	"::1/128",
+	// ULA reserved
+	"fc00::/7",
+	// link local
+	"fe80::/10",
+}
+
+func init() {
+	Private4 = parsePrivateCIDR(privateCIDR4)
+	Private6 = parsePrivateCIDR(privateCIDR6)
+}
+
+func parsePrivateCIDR(cidrs []string) []*net.IPNet {
+	ipnets := make([]*net.IPNet, len(cidrs))
+	for i, cidr := range cidrs {
+		_, ipnet, err := net.ParseCIDR(cidr)
+		if err != nil {
+			panic(err)
+		}
+		ipnets[i] = ipnet
+	}
+	return ipnets
+}
+
+// IsPublicAddr retruns true if the IP part of the multiaddr is not in a private network
+func IsPublicAddr(a ma.Multiaddr) bool {
+	ip, err := a.ValueForProtocol(ma.P_IP4)
+	if err == nil {
+		return !inAddrRange(ip, Private4)
+	}
+
+	ip, err = a.ValueForProtocol(ma.P_IP6)
+	if err == nil {
+		return !inAddrRange(ip, Private6)
+	}
+
+	return false
+}
+
+func inAddrRange(s string, ipnets []*net.IPNet) bool {
+	ip := net.ParseIP(s)
+	for _, ipnet := range ipnets {
+		if ipnet.Contains(ip) {
+			return true
+		}
+	}
+
+	return false
+}