ZyXEL P-202H User Guide - Page 131

P-202H Plus v2 User's Guide Table 38 Advanced Rule Setup (continued) LABEL DESCRIPTION End Enter a port number in this field to define a port range. This port number must be greater than that specified in the previous field (or equal to it for configuring an individual port). Phase 1 A phase 1 exchange establishes an IKE SA (Security Association). Negotiation Mode Select Main or Aggressive from the drop-down list box. The ZyXEL Device's negotiation mode should be identical to that on the remote secure gateway. Pre-Shared Key Type your pre-shared key in this field. A pre-shared key identifies a communicating party during a phase 1 IKE negotiation. It is called "preshared" because you have to share it with another party before you can communicate with them over a secure connection. Type from 8 to 31 case-sensitive ASCII characters or from 16 to 62 hexadecimal ("0-9", "A-F") characters. You must precede a hexadecimal key with a "0x" (zero x), which is not counted as part of the 16 to 62 character range for the key. For example, in "0x0123456789ABCDEF", "0x" denotes that the key is hexadecimal and "0123456789ABCDEF" is the key itself. Both ends of the VPN tunnel must use the same pre-shared key. You will receive a "PYLD_MALFORMED" (payload malformed) packet if the same preshared key is not used on both ends. Encryption Algorithm Select DES or 3DES from the drop-down list box. The ZyXEL Device's encryption algorithm should be identical to the secure remote gateway. When DES is used for data communications, both sender and receiver must know the same secret key, which can be used to encrypt and decrypt the message. The DES encryption algorithm uses a 56-bit key. Triple DES (3DES) is a variation on DES that uses a 168-bit key. As a result, 3DES is more secure than DES. It also requires more processing power, resulting in increased latency and decreased throughput. Authentication Algorithm Select SHA1 or MD5 from the drop-down list box. The ZyXEL Device's authentication algorithm should be identical to the secure remote gateway. MD5 (Message Digest 5) and SHA1 (Secure Hash Algorithm) are hash algorithms used to authenticate the source and integrity of packet data. The SHA1 algorithm is generally considered stronger than MD5, but is slower. Select SHA-1 for maximum security. SA Life Time Define the length of time before an IKE SA automatically renegotiates in this field. It may range from 60 to 3,000,000 seconds (almost 35 days). A short SA Life Time increases security by forcing the two VPN gateways to update the encryption and authentication keys. However, every time the VPN tunnel renegotiates, all users accessing remote resources are temporarily disconnected. Key Group You must choose a key group for phase 1 IKE setup. DH1 (default) refers to Diffie-Hellman Group 1 a 768 bit random number. DH2 refers to Diffie-Hellman Group 2 a 1024 bit (1Kb) random number. Phase 2 A phase 2 exchange uses the IKE SA established in phase 1 to negotiate the SA for IPSec. Active Protocol Select ESP or AH from the drop-down list box. The ZyXEL Device's IPSec Protocol should be identical to the secure remote gateway. The ESP (Encapsulation Security Payload) protocol (RFC 2406) provides encryption as well as the authentication offered by AH. If you select ESP here, you must select options from the Encryption Algorithm and Authentication Algorithm fields (described below). The AH protocol (Authentication Header Protocol) (RFC 2402) was designed for integrity, authentication, sequence integrity (replay resistance), and non-repudiation but not for confidentiality, for which the ESP was designed. If you select AH here, you must select options from the Authentication Algorithm field. Chapter 11 VPN Screens 130