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Chapter 11. Tunnels
The FB6000 supports the following tunnelling protocols :-
• IPsec (IP security)
• FB105 lightweight tunnelling protocol
• ETUN (Ether tunnelling)
IPsec is an implementation of the IPsec protocol and IKEv2 key management protocol, as defined in various
RFCs. This provides the means to authenticate and encrypt traffic sent over a public communication channel
(such as the Internet).
Ether tunnelling provides a mechanism to tunnel layer 2 ethernet traffic between two devices, using the protocol
defined in RFC3378.
Support for FB105 tunnels means the FB6000 can inter-work with existing FB105 hardware. FB105 tunnels
can also be set up between any two FireBricks from the FB2x00 and FB6000 ranges which support FB105
tunnelling.
11.1. IPsec (IP Security)
11.1.1. Introduction
One of the uses of IPsec is to create a private tunnel between two places. This could be two FireBricks, or
between a FireBrick and some other device such as a router, VPN box, Linux box, etc.
The tunnel allows traffic to IP addresses at the far end to be routed over the Internet in secret, encrypted at the
sending end and decrypted at the receiving end.
IPsec can also be used to set up a VPN between a roaming client and a server, providing security for working-
at-home or on-the-road scenarios. This usage is usually known as a Road Warrior connection. The FireBrick
can be used as the server for Road Warrior connections; it cannot act as a Road Warrior client.
There are three main aspects to IP Security: integrity checking, encryption and authentication.
11.1.1.1. Integrity checking
The purpose of integrity checking is to ensure that the packets of data when received are identical to when
transmitted - i.e. their contents have not been tampered with en route.
There are a number of algorithms that can be used to implement integrity checking. They all use a key which is
known only to the two ends of the communication. The key is typically a sequence of random-looking bytes,
usually expressed in hex notation.
Integrity checking on its own does not stop someone snooping on the contents of the packets, it just makes
sure that they are not tampered with on the way (as only someone with knowledge of the key could change
the data without invalidating it).
11.1.1.2. Encryption
The purpose of encryption is to change the data when it is sent so that nobody snooping on the packet can
make sense of it. There are many different algorithms, offering different levels of security. Encryption similarly
involves a key which is known only to the two ends of the communication.
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