BGP routers only advertise the best path to their neighbors. When a better path is found, it replaces the current path. Advertising a path and replacing it with a new path is called an implicit withdraw. Since we only advertise the best path, a lot of other possible paths are unknown to some of the… Read More »
There are 3 ways of advertising default route in BGP. Method 1: Using network 0.0.0.0 command. It requires only that the route 0.0.0.0 is present in the Interior Gateway Protocol (IGP) routing table. This is the preferred approach. Method 2: Using default-information originate command. It requires explicit redistribution of the route 0.0.0.0. This protects against… Read More »
PPTP:To allow PPTP tunnel maintenance traffic, open TCP 1723.To allow PPTP tunneled data to pass through router, open Protocol ID 47. L2TP over IPSecTo allow Internet Key Exchange (IKE), open UDP 500.To allow IPSec Network Address Translation (NAT-T) open UDP 4500.To allow L2TP traffic, open UDP 1701. OpenVPN: OpenVPN uses port 1194 udp and… Read More »