Configuring BGP routing protocol

• #router bgp {AS no.}
•  #network {network ID} mask [subnet mask] – When you dont put mask the router will assume default classfull mask
•  #neighbor {IP address} remote-as {AS No.}
• BEWARE!! In BGP there is rule that states: router looks exactly what you type in network command with the mask also! If the router cannot find it it will not announce anything. If the exact route is not in routing table you cann add static route pointing to null interface and route can be announced. So whenever you are advertising route in BGP via network command be sure it match
• #neighbor {IP address} password {password} – by this command you specify the authentication
• #neighbor {IP address} version {version number} – by this command you allow only specified version to run between BGP neighbors

Using loopbacks

For neighbor IP address you should use loopback interface. Why? When you specify physical interface and that interface will go down, your neihborship wil go down also. But when you specify loopback interface and physical interface will go down via you reach the neighbor, then you can use alternate path to reach the neighbor.

That means that using loopback itnerfaces brings you redundancy.