Tuesday, November 19, 2024

Site-to-Site IPSec VPN with EasyVPN NEM: Old vs New Router (Post-Cisco IOS 15.9(3)M10)

Cisco's IOS 15.9(3)M10 introduces improvements and potential changes to VPN configurations, especially when implementing site-to-site IPSec VPN using **EasyVPN Network Extension Mode (NEM)**. Below is a comparison of configuring an **old router** versus a **new router** post-15.9(3)M10 for this type of VPN:
---
### **Old Router (Pre-IOS 15.9(3)M10)**
1. **EasyVPN NEM Basics**:
   - EasyVPN Network Extension Mode (NEM) extends the corporate network to the branch, treating the remote site as part of the main network.
   - Commonly used commands:
     - `crypto ipsec client ezvpn`
     - NEM mode set with `mode network-extension`.
2. **Configuration Example**:
   crypto ipsec client ezvpn CLIENT
      connect auto
      group GROUP_NAME key GROUP_KEY
      mode network-extension
      peer 203.0.113.1
      xauth userid local
      username USERNAME password PASSWORD
   interface Tunnel0
      ip address negotiated
      tunnel source GigabitEthernet0/0
      tunnel mode ipsec ipv4
      crypto ipsec client ezvpn CLIENT
3. **Limitations**:
   - No support for modern algorithms (e.g., AES-GCM or SHA-2).
   - Legacy encryption profiles (DES, 3DES).
   - Static negotiation and legacy group settings.
---
### **New Router (Post-IOS 15.9(3)M10)**
1. **Key Enhancements in IOS 15.9(3)M10**:
   - Improved support for modern cryptographic standards:
     - AES-GCM, AES-256.
     - SHA-2 for integrity.
   - Streamlined configuration for enhanced security and efficiency.
   - Easier integration with modern IKEv2 standards.
2. **Configuration Changes**:
   - Replace `crypto ipsec client ezvpn` with IKEv2-based configurations.
   - Use Virtual Tunnel Interface (VTI) for scalability and better flexibility.
   - Include modern security proposals (AES, DH groups, SHA-2).
   - Improved XAUTH and user-based authentication.
3. **Configuration Example**:
   crypto ikev2 proposal VPN-PROPOSAL
      encryption aes-cbc-256
      integrity sha256
      group 14
   crypto ikev2 policy VPN-POLICY
      proposal VPN-PROPOSAL
   crypto ikev2 keyring VPN-KEYRING
      peer PEER1
         address 203.0.113.1
         pre-shared-key GROUP_KEY
   crypto ikev2 profile VPN-PROFILE
      match identity remote address 203.0.113.1 255.255.255.255
      authentication remote pre-share
      authentication local pre-share
      keyring local VPN-KEYRING
   crypto ipsec transform-set TRANSFORM esp-aes 256 esp-sha256-hmac
   crypto ipsec profile IPSEC-PROFILE
      set transform-set TRANSFORM
      set ikev2-profile VPN-PROFILE
   interface Tunnel0
      ip address negotiated
      tunnel source GigabitEthernet0/0
      tunnel mode ipsec ipv4
      tunnel protection ipsec profile IPSEC-PROFILE
4. **Benefits**:
   - Enhanced security with modern encryption and hashing.
   - Scalability with VTI instead of EasyVPN NEM.
   - Improved interoperability with other vendors and newer Cisco devices.
---
**Migration Note**: If you are migrating from an older EasyVPN NEM setup to a new router with IOS 15.9(3)M10, it is advisable to redesign using IKEv2 and VTIs to leverage modern capabilities while maintaining compatibility with legacy configurations if required.

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