Billion BiPAC 8900X R3, User Manual, Page: 163 / 261

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IPSec for L2TP
Connection Name: A given name for the connection, but it should contain no spaces (e.g.
“connection-to-office”).
WAN Interface: Select the set interface for the IPSec tunnel.
Remote Security Gateway: Input the IP of remote security gateway.
Key Exchange Method: Displays key exchange method.
Pre-Shared Key: This is for the Internet Key Exchange (IKE) protocol, a string from 1 to 32
characters. Both sides should use the same key. IKE is used to establish a shared security policy
and authenticated keys for services (such as IPSec) that require a key. Before any IPSec traffic can
be passed, each router must be able to verify the identity of its peer. This can be done by manually
entering the pre-shared key into both sides (router or hosts).
Encryption Algorithm: Select the encryption algorithm from the drop-down menu. There are
several options: 3DES and AES (128, 192 and 256). 3DES and AES are more powerful but
increase latency.
3DES: Stands for Triple Data Encryption Standard, it uses 168 (56*3) bits as an encryption
method.
AES: Stands for Advanced Encryption Standards, you can use 128, 192 or 256 bits as
encryption method.
Integrity Algorithm: Authentication establishes the integrity of the datagram and ensures it is not
tampered with in transmit. There are 2 options: Message Digest 5 (MD5) and Secure Hash
Algorithm (SHA1). SHA1 is more resistant to brute-force attacks than MD5. However, it is slower.
MD5: A one-way hashing algorithm that produces a 128−bit hash.
SHA1: A one-way hashing algorithm that produces a 160−bit hash.
DH Group: It is a public-key cryptography protocol that allows two parties to establish a shared
secret over an unsecured communication channel (i.e. over the Internet). MODP stands for Modular
Exponentiation Groups.
IPSec Lifetime: Specify the number of minutes that IPSec will stay active before new encryption
and authentication key will be exchanged. Enter a value to negotiate and establish secure
authentication. Default is 60 minutes (3600 seconds). A short time increases security by forcing the
two parties to update the keys. However, every time when the VPN tunnel re- negotiates, access
through the tunnel will be temporarily disconnected.