Cisco Cisco IOS Software Release 12.4(2)T Prospecto

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37

ƒ Firewall looks at the signaling to 

determine what ports media will flow 

through; FWs also have the ability to 

create zones for this protection

ƒ If you upgrade a voice application 

server the firewall might be affected

ƒ If the FW does not see signaling 

(encrypted, asymmetrical path) then 

media ports cannot be opened

I see 

signaling, 

maybe valid 

call? Open 

media 

ports???

Valid Authorized 

Call Details

ƒ Firewall receives a hashed STUN 

message with details of an 

authorized call 

ƒ Protocol version independent
ƒ Secures Encrypted Signaling
ƒ Secures asymmetrical signaling and 

media paths