diff --git a/CHANGELOG.md b/CHANGELOG.md
index 63237135..8e8092e0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 ## Changelog
 
+### 12.81.0
+
+* `[knf/validators/network]` Added `HasIP` validator
+* `[strutil]` Added method `ReplaceIgnoreCase`
+* `[uuid]` `GenUUID4` renamed to `UUID4`
+* `[uuid]` `GenUUID5` renamed to `UUID5`
+* `[uuid]` Code refactoring
+
 ### 12.80.0
 
 * `[system]` Added ANSI color info to `OSInfo`
diff --git a/ek.go b/ek.go
index 71e3c8e3..d5cfa933 100644
--- a/ek.go
+++ b/ek.go
@@ -20,7 +20,7 @@ import (
 // ////////////////////////////////////////////////////////////////////////////////// //
 
 // VERSION is current ek package version
-const VERSION = "12.80.0"
+const VERSION = "12.81.0"
 
 // ////////////////////////////////////////////////////////////////////////////////// //
 
diff --git a/knf/validators/network/validators.go b/knf/validators/network/validators.go
index 80713ba5..34c9522b 100644
--- a/knf/validators/network/validators.go
+++ b/knf/validators/network/validators.go
@@ -33,6 +33,9 @@ var (
 
 	// URL returns error if config property isn't a valid URL
 	URL = validateURL
+
+	// HasIP returns error if system doesn't have interface with IP from config property
+	HasIP = validateHasIP
 )
 
 // ////////////////////////////////////////////////////////////////////////////////// //
@@ -82,7 +85,7 @@ func validateMAC(config *knf.Config, prop string, value any) error {
 		return fmt.Errorf("%s is not a valid MAC address: %v", macStr, err)
 	}
 
-	return err
+	return nil
 }
 
 func validateCIDR(config *knf.Config, prop string, value any) error {
@@ -98,7 +101,7 @@ func validateCIDR(config *knf.Config, prop string, value any) error {
 		return fmt.Errorf("%s is not a valid CIDR address: %v", cidrStr, err)
 	}
 
-	return err
+	return nil
 }
 
 func validateURL(config *knf.Config, prop string, value any) error {
@@ -114,5 +117,35 @@ func validateURL(config *knf.Config, prop string, value any) error {
 		return fmt.Errorf("%s is not a valid URL address: %v", urlStr, err)
 	}
 
-	return err
+	return nil
+}
+
+func validateHasIP(config *knf.Config, prop string, value any) error {
+	ipStr := config.GetS(prop)
+
+	if ipStr == "" {
+		return nil
+	}
+
+	interfaces, err := net.Interfaces()
+
+	if err != nil {
+		return fmt.Errorf("Can't get interfaces info for check: %v", err)
+	}
+
+	for _, i := range interfaces {
+		addr, err := i.Addrs()
+
+		if err != nil {
+			continue
+		}
+
+		for _, a := range addr {
+			if ipStr == a.(*net.IPNet).IP.String() {
+				return nil
+			}
+		}
+	}
+
+	return fmt.Errorf("The system does not have an interface with the address %s", ipStr)
 }
diff --git a/knf/validators/network/validators_test.go b/knf/validators/network/validators_test.go
index 5729b20a..802c0926 100644
--- a/knf/validators/network/validators_test.go
+++ b/knf/validators/network/validators_test.go
@@ -23,6 +23,7 @@ const _CONFIG_DATA = `
 	test0:
 	test1: 127.0.0.1
 	test2: 300.0.400.5
+	test3: 192.168.1.254
 
 [port]
 	test0:
@@ -83,6 +84,27 @@ func (s *ValidatorSuite) TestIPValidator(c *C) {
 	c.Assert(errs[0].Error(), Equals, "300.0.400.5 is not a valid IP address")
 }
 
+func (s *ValidatorSuite) TestHasIPValidator(c *C) {
+	configFile := createConfig(c, _CONFIG_DATA)
+
+	err := knf.Global(configFile)
+	c.Assert(err, IsNil)
+
+	errs := knf.Validate([]*knf.Validator{
+		{"ip:test0", HasIP, nil},
+		{"ip:test1", HasIP, nil},
+	})
+
+	c.Assert(errs, HasLen, 0)
+
+	errs = knf.Validate([]*knf.Validator{
+		{"ip:test3", HasIP, nil},
+	})
+
+	c.Assert(errs, HasLen, 1)
+	c.Assert(errs[0].Error(), Equals, "The system does not have an interface with the address 192.168.1.254")
+}
+
 func (s *ValidatorSuite) TestPortValidator(c *C) {
 	configFile := createConfig(c, _CONFIG_DATA)
 
diff --git a/strutil/example_test.go b/strutil/example_test.go
index 3f0464cd..b9205a79 100644
--- a/strutil/example_test.go
+++ b/strutil/example_test.go
@@ -122,6 +122,15 @@ func ExampleReplaceAll() {
 	// M???ag?
 }
 
+func ExampleReplaceIgnoreCase() {
+	fmt.Println(ReplaceIgnoreCase(
+		"User bob has no item. Add items to user Bob?", "bob", "[Bob]",
+	))
+
+	// Output:
+	// User [Bob] has no item. Add items to user [Bob]?
+}
+
 func ExampleFields() {
 	fmt.Printf("%#v\n", Fields("Bob  Alice, 'Mary Key', \"John Dow\""))
 
diff --git a/strutil/strutil.go b/strutil/strutil.go
index 7666d431..186904ae 100644
--- a/strutil/strutil.go
+++ b/strutil/strutil.go
@@ -234,8 +234,8 @@ func SuffixSize(str string, suffix rune) int {
 	return result
 }
 
-// ReplaceAll replaces all symbols in given string
-func ReplaceAll(source, from, to string) string {
+// ReplaceAll replaces all symbols from replset in string
+func ReplaceAll(source, replset, to string) string {
 	if source == "" {
 		return ""
 	}
@@ -244,7 +244,7 @@ func ReplaceAll(source, from, to string) string {
 
 SOURCELOOP:
 	for _, sourceSym := range source {
-		for _, fromSym := range from {
+		for _, fromSym := range replset {
 			if fromSym == sourceSym {
 				result.WriteString(to)
 				continue SOURCELOOP
@@ -257,6 +257,35 @@ SOURCELOOP:
 	return result.String()
 }
 
+// ReplaceIgnoreCase replaces part of the string ignoring case
+func ReplaceIgnoreCase(source, from, to string) string {
+	if source == "" || from == "" {
+		return source
+	}
+
+	var result strings.Builder
+
+	from = strings.ToLower(from)
+	lowSource := strings.ToLower(source)
+
+	for {
+		index := strings.Index(lowSource, from)
+
+		if index == -1 {
+			result.WriteString(source)
+			break
+		}
+
+		result.WriteString(source[:index])
+		result.WriteString(to)
+
+		source = source[index+len(from):]
+		lowSource = lowSource[index+len(from):]
+	}
+
+	return result.String()
+}
+
 // Exclude excludes substring from given string
 func Exclude(data, substr string) string {
 	if len(data) == 0 || len(substr) == 0 {
diff --git a/strutil/strutil_test.go b/strutil/strutil_test.go
index 5e2f38f1..0acb6a86 100644
--- a/strutil/strutil_test.go
+++ b/strutil/strutil_test.go
@@ -125,6 +125,13 @@ func (s *StrUtilSuite) TestReplaceAll(c *C) {
 	c.Assert(ReplaceAll("", "AB12", "?"), Equals, "")
 }
 
+func (s *StrUtilSuite) TestReplaceIgnoreCase(c *C) {
+	c.Assert(ReplaceIgnoreCase("ABCD1234abcd1234AbCd11ABcd", "abcd", "????"), Equals, "????1234????1234????11????")
+	c.Assert(ReplaceIgnoreCase("TESTtestTEST", "abcd", "????"), Equals, "TESTtestTEST")
+	c.Assert(ReplaceIgnoreCase("", "abcd", "????"), Equals, "")
+	c.Assert(ReplaceIgnoreCase("ABCD1234abcd1234AbCd11ABcd", "abcd", ""), Equals, "1234123411")
+}
+
 func (s *StrUtilSuite) TestFields(c *C) {
 	c.Assert(Fields(""), IsNil)
 	c.Assert(Fields(""), HasLen, 0)
@@ -252,3 +259,9 @@ func (s *StrUtilSuite) BenchmarkReplaceAll(c *C) {
 		ReplaceAll("ABCDABCD12341234", "AB12", "?")
 	}
 }
+
+func (s *StrUtilSuite) BenchmarkReplaceIgnoreCase(c *C) {
+	for i := 0; i < c.N; i++ {
+		ReplaceIgnoreCase("ABCD1234abcd1234AbCd11ABcd", "abcd", "????")
+	}
+}
diff --git a/uuid/example_test.go b/uuid/example_test.go
index 86124f59..acd1b2cf 100644
--- a/uuid/example_test.go
+++ b/uuid/example_test.go
@@ -13,14 +13,10 @@ import (
 
 // ////////////////////////////////////////////////////////////////////////////////// //
 
-func ExampleGenUUID() {
-	fmt.Printf("UUID: %s\n", GenUUID())
+func ExampleUUID4() {
+	fmt.Printf("UUID v4: %s\n", UUID4().String())
 }
 
-func ExampleGenUUID4() {
-	fmt.Printf("UUID v4: %s\n", GenUUID4())
-}
-
-func ExampleGenUUID5() {
-	fmt.Printf("UUID v5: %s\n", GenUUID5(NsURL, "http://www.domain.com"))
+func ExampleUUID5() {
+	fmt.Printf("UUID v5: %s\n", UUID5(NsURL, "http://www.domain.com").String())
 }
diff --git a/uuid/uuid.go b/uuid/uuid.go
index 89ef00e9..747467ff 100644
--- a/uuid/uuid.go
+++ b/uuid/uuid.go
@@ -26,26 +26,26 @@ var (
 
 // ////////////////////////////////////////////////////////////////////////////////// //
 
-// GenUUID generates v4 UUID (Universally Unique Identifier)
-func GenUUID() string {
-	return GenUUID4()
-}
+// UUID contains UUID data
+type UUID []byte
 
-// GenUUID4 generates random generated UUID
-func GenUUID4() string {
-	uuid := make([]byte, 16)
+// ////////////////////////////////////////////////////////////////////////////////// //
+
+// UUID4 generates random generated UUID v4
+func UUID4() UUID {
+	uuid := make(UUID, 16)
 
 	rand.Read(uuid)
 
-	uuid[6] = (uuid[6] & 0X0F) | 0X40
-	uuid[8] = (uuid[8] & 0X3F) | 0X80
+	uuid[6] = (uuid[6] & 0x0F) | 0x40
+	uuid[8] = (uuid[8] & 0x3F) | 0x80
 
-	return toString(uuid)
+	return UUID(uuid)
 }
 
-// GenUUID5 generates UUID based on SHA-1 hash of namespace UUID and name
-func GenUUID5(ns []byte, name string) string {
-	uuid := make([]byte, 16)
+// UUID5 generates UUID v5 based on SHA-1 hash of namespace UUID and name
+func UUID5(ns []byte, name string) UUID {
+	uuid := make(UUID, 16)
 
 	hash := sha1.New()
 	hash.Write(ns)
@@ -53,26 +53,52 @@ func GenUUID5(ns []byte, name string) string {
 
 	copy(uuid, hash.Sum(nil))
 
-	uuid[6] = (uuid[6] & 0X0F) | 0x50
-	uuid[8] = (uuid[8] & 0X3F) | 0x80
+	uuid[6] = (uuid[6] & 0x0F) | 0x50
+	uuid[8] = (uuid[8] & 0x3F) | 0x80
 
-	return toString(uuid)
+	return UUID(uuid)
 }
 
 // ////////////////////////////////////////////////////////////////////////////////// //
 
-func toString(uuid []byte) string {
+// String returns string representation of UUID
+func (u UUID) String() string {
 	buf := make([]byte, 36)
 
-	hex.Encode(buf[0:8], uuid[0:4])
+	hex.Encode(buf[0:8], u[0:4])
 	buf[8] = '-'
-	hex.Encode(buf[9:13], uuid[4:6])
+	hex.Encode(buf[9:13], u[4:6])
 	buf[13] = '-'
-	hex.Encode(buf[14:18], uuid[6:8])
+	hex.Encode(buf[14:18], u[6:8])
 	buf[18] = '-'
-	hex.Encode(buf[19:23], uuid[8:10])
+	hex.Encode(buf[19:23], u[8:10])
 	buf[23] = '-'
-	hex.Encode(buf[24:], uuid[10:])
+	hex.Encode(buf[24:], u[10:])
 
 	return string(buf)
 }
+
+// ////////////////////////////////////////////////////////////////////////////////// //
+
+// GenUUID generates v4 UUID (Universally Unique Identifier)
+//
+// Deprecated: Use method UUID4.String() instead
+func GenUUID() string {
+	return UUID4().String()
+}
+
+// GenUUID4 generates random generated UUID
+//
+// Deprecated: Use method UUID4.String() instead
+func GenUUID4() string {
+	return UUID4().String()
+}
+
+// GenUUID5 generates UUID based on SHA-1 hash of namespace UUID and name
+//
+// Deprecated: Use method UUID5.String() instead
+func GenUUID5(ns []byte, name string) string {
+	return UUID5(ns, name).String()
+}
+
+// ////////////////////////////////////////////////////////////////////////////////// //
diff --git a/uuid/uuid_test.go b/uuid/uuid_test.go
index aed27f77..5c51a7d2 100644
--- a/uuid/uuid_test.go
+++ b/uuid/uuid_test.go
@@ -25,18 +25,19 @@ var _ = Suite(&UUIDSuite{})
 
 // ////////////////////////////////////////////////////////////////////////////////// //
 
-func (s *UUIDSuite) TestGenUUID(c *C) {
-	c.Assert(GenUUID(), HasLen, 36)
-	c.Assert(GenUUID(), Not(Equals), "00000000-0000-0000-0000-000000000000")
-}
-
 func (s *UUIDSuite) TestGenUUID4(c *C) {
-	c.Assert(GenUUID4(), HasLen, 36)
-	c.Assert(GenUUID4(), Not(Equals), "00000000-0000-0000-0000-000000000000")
+	c.Assert(UUID4(), HasLen, 16)
+	c.Assert(UUID4().String(), Not(Equals), "00000000-0000-0000-0000-000000000000")
 }
 
 func (s *UUIDSuite) TestGenUUID5(c *C) {
-	c.Assert(GenUUID5(NsURL, "TEST"), HasLen, 36)
+	c.Assert(UUID5(NsURL, "TEST"), HasLen, 16)
+	c.Assert(UUID5(NsURL, "TEST").String(), Not(Equals), "00000000-0000-0000-0000-000000000000")
+}
+
+func (s *UUIDSuite) TestDeprecated(c *C) {
+	c.Assert(GenUUID(), Not(Equals), "00000000-0000-0000-0000-000000000000")
+	c.Assert(GenUUID4(), Not(Equals), "00000000-0000-0000-0000-000000000000")
 	c.Assert(GenUUID5(NsURL, "TEST"), Not(Equals), "00000000-0000-0000-0000-000000000000")
 }