Ccna routing and Switching Complete Study Guide

Data integrity    Data integrity allows the receiver to verify that the data received was not 

altered in any way along the way. IPsec uses checksums as a simple check of the data.

Authentication    Authentication ensures that the connection is made with the correct 

partner. The receiver can authenticate the source of the packet by guaranteeing and 

certifying the source of the information.

Anti-replay service    Anti-replay election is based upon the receiver, meaning the service 

is effective only if the receiver checks the sequence number. In case you were wondering, a 

replay attack is when a hacker nicks a copy of an authenticated packet and later transmits 

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GRE Tunnels 

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it to the intended destination. When the duplicate, authenticated IP packet gets to the des-

tination, it can disrupt services and generally wreak havoc. The Sequence Number field is 

designed to foil this type of attack.

Traffic flow    For traffic flow confidentiality to work, you have to have at least tunnel 

mode selected. It’s most effective if it’s implemented at a security gateway where tons of 

traffic amasses because it’s precisely the kind of environment that can mask the true source-

destination patterns to bad guys who are trying to breach your network’s security.

Encryption

VPNs create a private network over a public network infrastructure, but to maintain 

confidentiality and security, we really need to use IPsec with our VPNs. IPsec uses various 

types of protocols to perform encryption. The types of encryption algorithms used today 

are as follows: