diff --git a/subscriptions/network-manager/src/hw_address.rs b/subscriptions/network-manager/src/hw_address.rs
index db29158..eb49769 100644
--- a/subscriptions/network-manager/src/hw_address.rs
+++ b/subscriptions/network-manager/src/hw_address.rs
@@ -1,38 +1,102 @@
-#[derive(Copy, Clone, PartialEq, Eq, Default, Debug, PartialOrd, Ord)]
+#[derive(Clone, PartialEq, Eq, Default, Debug, PartialOrd, Ord)]
 pub struct HwAddress {
-    address: u64,
+    octets: Vec<u8>,
 }
 
 impl HwAddress {
     pub fn from_str(arg: &str) -> Option<Self> {
-        let columnless_vec = arg.split(":").collect::<Vec<&str>>();
-        if columnless_vec.len() * 3 - 1 != arg.len() {
+        let segments: Vec<&str> = arg.split(":").collect();
+
+        // Only accept 6-byte (EUI-48) or 8-byte (EUI-64) addresses
+        if segments.len() != 6 && segments.len() != 8 {
             return None;
         }
-        for byte in &columnless_vec {
-            if byte.len() != 2 {
+
+        let mut octets: Vec<u8> = Vec::new();
+        for segment in segments {
+            if segment.len() != 2 {
                 return None;
             }
+            let byte: u8 = u8::from_str_radix(segment, 16).ok()?;
+            octets.push(byte);
         }
-        u64::from_str_radix(columnless_vec.join("").as_str(), 16)
-            .ok()
-            .map(|address| HwAddress { address })
-    }
-    pub fn from_string(arg: &str) -> Option<Self> {
-        HwAddress::from_str(arg)
+
+        Some(HwAddress { octets })
     }
 }
 
 impl std::fmt::Display for HwAddress {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        let hex = format!("{:#x}", self.address)
-            .trim_start_matches("0x")
-            .chars()
-            .collect::<Vec<_>>()
-            .chunks(2)
-            .map(|chunk| chunk.iter().cloned().collect::<String>())
-            .collect::<Vec<String>>()
-            .join(":");
-        write!(f, "{}", hex)
+        let hex_parts: Vec<String> = self
+            .octets
+            .iter()
+            .map(|byte| format!("{:02x}", byte))
+            .collect();
+        write!(f, "{}", hex_parts.join(":"))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_valid_6_byte_mac() {
+        let mac: &str = "00:11:22:33:44:55";
+        let hw_addr: HwAddress = HwAddress::from_str(mac).expect("should parse valid MAC");
+
+        // Access the internal octets field
+        assert_eq!(hw_addr.octets.len(), 6);
+        assert_eq!(hw_addr.octets, vec![0x00, 0x11, 0x22, 0x33, 0x44, 0x55]);
+    }
+
+    #[test]
+    fn test_display_6_byte_mac() {
+        let hw_addr: HwAddress = HwAddress {
+            octets: vec![0x00, 0x11, 0x22, 0x33, 0x44, 0x55],
+        };
+
+        assert_eq!(format!("{}", hw_addr), "00:11:22:33:44:55");
+    }
+
+    #[test]
+    fn test_parse_valid_8_byte_mac() {
+        let mac: &str = "00:11:22:33:44:55:66:77";
+        let hw_addr: HwAddress = HwAddress::from_str(mac).expect("should parse valid EUI-64 MAC");
+
+        assert_eq!(hw_addr.octets.len(), 8);
+        assert_eq!(
+            hw_addr.octets,
+            vec![0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77]
+        );
+    }
+
+    #[test]
+    fn test_display_8_byte_mac() {
+        let hw_addr: HwAddress = HwAddress {
+            octets: vec![0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77],
+        };
+
+        assert_eq!(format!("{}", hw_addr), "00:11:22:33:44:55:66:77");
+    }
+
+    #[test]
+    fn test_reject_invalid_length_macs() {
+        let invalid_macs: Vec<(&str, &str)> = vec![
+            ("00", "1-byte MAC"),
+            ("00:11:22:33", "4-byte MAC"),
+            ("00:11:22:33:44", "5-byte MAC"),
+            ("00:11:22:33:44:55:66", "7-byte MAC"),
+            ("00:11:22:33:44:55:66:77:88", "9-byte MAC"),
+            ("00:11:22:33:44:55:66:77:88:99:aa:bb", "12-byte MAC"),
+        ];
+
+        for (mac, description) in invalid_macs {
+            assert!(
+                HwAddress::from_str(mac).is_none(),
+                "should reject {}",
+                description
+            );
+        }
     }
 }