HP TMS zl Module Security Administrator's Guide

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Configuring a VPN on the HP TMS zl Module
GRE Tunnels
c. If you selected Preshared Key, type a string of 12 to 49 alphanumeric
or special characters in the Preshared Key box. Type the same string
in the Confirm Preshared Key box.
The string (which is case-sensitive) must match that configured on
the remote gateway.
14. Under Security Parameters Proposal, configure the security settings pro-
posed by the TMS zl Module for the IKE SA:
a. For Diffie-Hellman (DH) Group, select the group for the Diffie-Hellman
exchange:
– Group 1 (768)
– Group 2 (1024)
– Group 5 (1536)
The group determines the length of the prime number used during the
exchange. The larger the number, the more secure the key generated
by the exchange.
b. For Encryption Algorithm, select one of these protocols, listed from
least secure (and least processor-intensive) to most:
–DES
– AES128 (16)
–3DES
– AES192 (24)
– AES256 (32)
The number in parentheses after AES options indicates the key length
for the algorithm in bytes.
c. For Authentication Algorithm, select one of these protocols, listed from
least secure (and least processor-intensive) to most:
–MD5
–SHA-1
d. For SA Lifetime in Seconds, type the number of seconds that the IKE
SA is kept open.
Valid values are between 300 seconds and 86400 seconds (1 day). The
default value is 28800 (8 hours).
Remember that this setting applies to the IKE SA, which is a tempo-
rary tunnel used only to establish the IPsec SA.
15. Click Next.