NHRP clients register themselves with the NHRP server and report their public IP address NHC sends a query to the NHS if they want to communicate with another NHC.All other routers will be the NHRP client's next-hop client (NHC).One router will be the NHRP server next-hop server (NHS).NHRP Provides layer 2 address resolution protocol and caching services similar to ARP and inverse ARP. All it does is build a dynamic database store on the hub with information about spokes IP addresses. We want something which can help our router to figure out what the public IP address is of the other router, we do this with the help of a protocol called NHRP (Next Hop Resolution Protocol). Next hop resolution protocol (NHRP) Maps the tunnel IP with NBMA address (public IP ) (static or dynamic). The endpoint can be configured as GRE or MGRE and Mapping is done by NHRP Protocol. the Tunnel can have many endpoints by using a single tunnel interface. Multipoint GRE(Mgre) Uses tunnel source and tunnel mode (mgre). It keeps costs low, minimizing configuration complexity, and increasing flexibility. but When we use GRE Multipoint, there will be only one tunnel interface on each router. mGRE interfaces do not have a tunnel destination.
It becomes messy quickly so much point-to-point tunnels. Our regular GRE tunnels are point-to-point and don’t scale well. This technology has been developed to address the need for automatically created VPN tunnels when dynamic IP addresses on the spokes are in use. This pure hub-and-spoke topology where all branches may communicate with each other securely through the hub. Before you configure you must adjust (MTU) maximum transfer unit and MSS maximum segment size. Each tunnel interface is assigned an IP address within the same network as other Tunnel interfaces. GRE tunnel uses a ‘tunnel’ interface a logical interface configured on the router with an IP address where packets are encapsulated and decapsulated as they enter or exit the GRE tunnel.Īll tunnel interfaces of participated routers must always be configured with an IP address that is not used anywhere else in the network.
DMVPN LAB CCNP MANUAL
( That’s the reason we used IPSec to add an encryption layer and secure the GRE tunnel with the help of IPSec we get army-level encryption).Ĭlassic GRE tunnel is a point to point, Manual tunnel, Not scalable, Static IP on all endpoints When we create a GRE point-to-point tunnel without any encryption is extremely risky as sensitive data can easily be extracted from the tunnel and misused by others. GRE tunnel is an encapsulation protocol and does not perform any encryption. Generic Routing Encapsulation (GRE) has some disadvantages:. GRE is used when packets need to be sent from one network to another over the internet. Generic Routing Encapsulation (GRE) is a network tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links or point-to-multipoint links over an Internet Protocol network.
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