diff --git a/server/lib/ip.ts b/server/lib/ip.ts
index 88c64acc..62cf1d2d 100644
--- a/server/lib/ip.ts
+++ b/server/lib/ip.ts
@@ -3,24 +3,98 @@ interface IPRange {
     end: bigint;
 }
 
+type IPVersion = 4 | 6;
+
 /**
- * Converts IP address string to BigInt for numerical operations
+ * Detects IP version from address string
+ */
+function detectIpVersion(ip: string): IPVersion {
+    return ip.includes(':') ? 6 : 4;
+}
+
+/**
+ * Converts IPv4 or IPv6 address string to BigInt for numerical operations
  */
 function ipToBigInt(ip: string): bigint {
-    return ip.split('.')
-        .reduce((acc, octet) => BigInt.asUintN(64, (acc << BigInt(8)) + BigInt(parseInt(octet))), BigInt(0));
+    const version = detectIpVersion(ip);
+    
+    if (version === 4) {
+        return ip.split('.')
+            .reduce((acc, octet) => {
+                const num = parseInt(octet);
+                if (isNaN(num) || num < 0 || num > 255) {
+                    throw new Error(`Invalid IPv4 octet: ${octet}`);
+                }
+                return BigInt.asUintN(64, (acc << BigInt(8)) + BigInt(num));
+            }, BigInt(0));
+    } else {
+        // Handle IPv6
+        // Expand :: notation
+        let fullAddress = ip;
+        if (ip.includes('::')) {
+            const parts = ip.split('::');
+            if (parts.length > 2) throw new Error('Invalid IPv6 address: multiple :: found');
+            const missing = 8 - (parts[0].split(':').length + parts[1].split(':').length);
+            const padding = Array(missing).fill('0').join(':');
+            fullAddress = `${parts[0]}:${padding}:${parts[1]}`;
+        }
+
+        return fullAddress.split(':')
+            .reduce((acc, hextet) => {
+                const num = parseInt(hextet || '0', 16);
+                if (isNaN(num) || num < 0 || num > 65535) {
+                    throw new Error(`Invalid IPv6 hextet: ${hextet}`);
+                }
+                return BigInt.asUintN(128, (acc << BigInt(16)) + BigInt(num));
+            }, BigInt(0));
+    }
 }
 
 /**
  * Converts BigInt to IP address string
  */
-function bigIntToIp(num: bigint): string {
-    const octets: number[] = [];
-    for (let i = 0; i < 4; i++) {
-        octets.unshift(Number(num & BigInt(255)));
-        num = num >> BigInt(8);
+function bigIntToIp(num: bigint, version: IPVersion): string {
+    if (version === 4) {
+        const octets: number[] = [];
+        for (let i = 0; i < 4; i++) {
+            octets.unshift(Number(num & BigInt(255)));
+            num = num >> BigInt(8);
+        }
+        return octets.join('.');
+    } else {
+        const hextets: string[] = [];
+        for (let i = 0; i < 8; i++) {
+            hextets.unshift(Number(num & BigInt(65535)).toString(16).padStart(4, '0'));
+            num = num >> BigInt(16);
+        }
+        // Compress zero sequences
+        let maxZeroStart = -1;
+        let maxZeroLength = 0;
+        let currentZeroStart = -1;
+        let currentZeroLength = 0;
+
+        for (let i = 0; i < hextets.length; i++) {
+            if (hextets[i] === '0000') {
+                if (currentZeroStart === -1) currentZeroStart = i;
+                currentZeroLength++;
+                if (currentZeroLength > maxZeroLength) {
+                    maxZeroLength = currentZeroLength;
+                    maxZeroStart = currentZeroStart;
+                }
+            } else {
+                currentZeroStart = -1;
+                currentZeroLength = 0;
+            }
+        }
+
+        if (maxZeroLength > 1) {
+            hextets.splice(maxZeroStart, maxZeroLength, '');
+            if (maxZeroStart === 0) hextets.unshift('');
+            if (maxZeroStart + maxZeroLength === 8) hextets.push('');
+        }
+
+        return hextets.map(h => h === '0000' ? '0' : h.replace(/^0+/, '')).join(':');
     }
-    return octets.join('.');
 }
 
 /**
@@ -28,33 +102,56 @@ function bigIntToIp(num: bigint): string {
  */
 function cidrToRange(cidr: string): IPRange {
     const [ip, prefix] = cidr.split('/');
+    const version = detectIpVersion(ip);
     const prefixBits = parseInt(prefix);
     const ipBigInt = ipToBigInt(ip);
-    const mask = BigInt.asUintN(64, (BigInt(1) << BigInt(32 - prefixBits)) - BigInt(1));
+    
+    // Validate prefix length
+    const maxPrefix = version === 4 ? 32 : 128;
+    if (prefixBits < 0 || prefixBits > maxPrefix) {
+        throw new Error(`Invalid prefix length for IPv${version}: ${prefix}`);
+    }
+
+    const shiftBits = BigInt(maxPrefix - prefixBits);
+    const mask = BigInt.asUintN(version === 4 ? 64 : 128, (BigInt(1) << shiftBits) - BigInt(1));
     const start = ipBigInt & ~mask;
     const end = start | mask;
+    
     return { start, end };
 }
 
 /**
  * Finds the next available CIDR block given existing allocations
  * @param existingCidrs Array of existing CIDR blocks
- * @param blockSize Desired prefix length for the new block (e.g., 24 for /24)
- * @param startCidr Optional CIDR to start searching from (default: "0.0.0.0/0")
+ * @param blockSize Desired prefix length for the new block
+ * @param startCidr Optional CIDR to start searching from
  * @returns Next available CIDR block or null if none found
  */
 export function findNextAvailableCidr(
     existingCidrs: string[],
     blockSize: number,
-    startCidr: string = "0.0.0.0/0"
+    startCidr?: string
 ): string | null {
+    if (existingCidrs.length === 0) return null;
+    
+    // Determine IP version from first CIDR
+    const version = detectIpVersion(existingCidrs[0].split('/')[0]);
+    // Use appropriate default startCidr if none provided
+    startCidr = startCidr || (version === 4 ? "0.0.0.0/0" : "::/0");
+    
+    // Ensure all CIDRs are same version
+    if (existingCidrs.some(cidr => detectIpVersion(cidr.split('/')[0]) !== version)) {
+        throw new Error('All CIDRs must be of the same IP version');
+    }
+
     // Convert existing CIDRs to ranges and sort them
     const existingRanges = existingCidrs
         .map(cidr => cidrToRange(cidr))
         .sort((a, b) => (a.start < b.start ? -1 : 1));
 
     // Calculate block size
-    const blockSizeBigInt = BigInt(1) << BigInt(32 - blockSize);
+    const maxPrefix = version === 4 ? 32 : 128;
+    const blockSizeBigInt = BigInt(1) << BigInt(maxPrefix - blockSize);
 
     // Start from the beginning of the given CIDR
     let current = cidrToRange(startCidr).start;
@@ -63,7 +160,6 @@ export function findNextAvailableCidr(
     // Iterate through existing ranges
     for (let i = 0; i <= existingRanges.length; i++) {
         const nextRange = existingRanges[i];
-
         // Align current to block size
         const alignedCurrent = current + ((blockSizeBigInt - (current % blockSizeBigInt)) % blockSizeBigInt);
 
@@ -74,7 +170,7 @@ export function findNextAvailableCidr(
 
         // If we're at the end of existing ranges or found a gap
         if (!nextRange || alignedCurrent + blockSizeBigInt - BigInt(1) < nextRange.start) {
-            return `${bigIntToIp(alignedCurrent)}/${blockSize}`;
+            return `${bigIntToIp(alignedCurrent, version)}/${blockSize}`;
         }
 
         // Move current pointer to after the current range
@@ -85,12 +181,19 @@ export function findNextAvailableCidr(
 }
 
 /**
-* Checks if a given IP address is within a CIDR range
-* @param ip IP address to check
-* @param cidr CIDR range to check against
-* @returns boolean indicating if IP is within the CIDR range
-*/
+ * Checks if a given IP address is within a CIDR range
+ * @param ip IP address to check
+ * @param cidr CIDR range to check against
+ * @returns boolean indicating if IP is within the CIDR range
+ */
 export function isIpInCidr(ip: string, cidr: string): boolean {
+    const ipVersion = detectIpVersion(ip);
+    const cidrVersion = detectIpVersion(cidr.split('/')[0]);
+    
+    if (ipVersion !== cidrVersion) {
+        throw new Error('IP address and CIDR must be of the same version');
+    }
+
     const ipBigInt = ipToBigInt(ip);
     const range = cidrToRange(cidr);
     return ipBigInt >= range.start && ipBigInt <= range.end;