Cisco gre tunnel static route

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GRE Tunnel Configuration with Cisco Packet Tracer

Here, we used Interface name. Lastly, we define the Tunnel Destination IP address. We will do the same configuration on Router 2, only IP addresses will change. Because, the routers needs to know how to reach to the users connected to the other end router. In other words, because of the fact that the other end LAN is not directly connected to the router, it needs routing information and we provide this with a Static Route. Your email address will not be published. Now, I am here to share my experiences with you…. Table of Contents. GRE Tunnel Overview. Leave a Reply Cancel reply Your email address will not be published. Contact info ipcisco. Subscribe to NewsLetter. IPCisco is the Winner! Search for: Search. From IPCisco Fans Very Useful and Very Well Written! The blog is very useful and very well written. It covers a variety of concepts and technologies from different vendors My students use IPCisco. It has recently been very useful in researching the use of IPv It has recently been very useful in researching the use of IPv6. Thank you for your support. Whenever I want to understand a topic from basic to expert level, IPCisco is the first site on my list

Generic Routing Encapsulation


In designing a VPN deployment for a customer, it is essential to integrate broader design considerations such as high availability, resiliency, IP multicast, and quality of service QoS. This chapter starts with an overview of some general design considerations that need to be factored into the design, followed by sections on implementation, high availability, QoS, and IP multicast. To provide redundancy, the branch router should have two or more tunnels to the campus headends. These headend routers can be geographically separated or co-located. For maximum protection, both headend and site redundancy should be implemented. This design guide focuses on a solution with only two point-to-point p2p GRE tunnels per branch terminating to two headend routers, to simplify the routing domain. The IPsec control plane uses dynamic crypto maps at the headend to minimize configuration changes in the event of new branches being added. Dynamic crypto maps are also implemented to support branches with a dynamic Internet address as their crypto peer. Alternatively, the IPsec tunnel protection feature can be configured on tunnel interfaces. The branch router can either have a static public interface IP address or one that is obtained dynamically from the service provider. For all topologies listed above, administrative configuration is required. These topologies are the most scalable and predominately mimic traditional Layer 2 leased line, Frame Relay, or ATM hub-and-spoke networks. Although partial mesh topologies are available, they are limited by both the routing protocol and the possibility of a dynamic public IP address. Configuring a partial mesh topology within a p2p GRE over IPsec design requires obtaining static public IP addresses for the branch routers that peer between each another. Full mesh topologies are available as well and have the same limitations as partial mesh topologies. However, considering the administrative overhead involved, a full mesh topology is not recommended in a p2p GRE over IPsec design. The following two headend system architectures are described in this design guide:. This architecture impacts scalability, where the central CPU becomes the gating factor. Both the routing and GRE control planes are housed on one routing process, while the IPsec control plane is housed on another. The reason for separating the functionality is to provide the best scalable solution given various platform limitations; specifically, CPU dependencies and resiliency. Proper address summarization is highly recommended because it accomplishes the following:. Although it is generally understood that VPNs are used for secure communications across a shared infrastructure such as the Internetmake sure to distinguish between the enterprise addressing space, sometimes referred to as the private or inside addresses; and the infrastructure addressing space, also referred to as the service provider, public, or outside addresses. In most p2p GRE over IPsec VPN designs, the outside interface of the router is addressed in the infrastructure or public address space assigned by the service provider, while the tunnel interface belongs to the enterprise private network address space. In a static p2p GRE over a static IPsec configuration, the tunnel interfaces are sourced and destined to the public addresses. However, in the dynamic crypto peer address and static p2p GRE configuration, the branch router crypto IP address is dynamically obtained. Although IPsec provides a secure method for tunneling data across an IP network, it has limitations. IPsec does not support IP broadcast or IP multicast, preventing the use of protocols that rely on these features, such as routing protocols. IPsec also does not support the use of multiprotocol traffic. Using GRE tunnels in conjunction with IPsec provides the ability to run a routing protocol, IP multicast IPmcor multiprotocol traffic across the network between the headend s and branch offices. GRE also enables private addressing. Without a tunnel protocol running, all end stations are required to be addressed with registered IP addresses.

GRE Tunnel Keepalives


GRE is developed by Cisco System. In order to configure the GRE tunnel, you must need connectivity between two remote routers through static Public IP address. GRE usages IP protocol number By default, GRE does not perform any kind of encryption. GRE is initially defined in rfc I have two different routers in two different locations. Router R1 has Public IP R1 and R2 can communicate using their Public IP addresses. We will use another subnet So, configuring the GRE tunnel by checking the connectivity between routers. Just open the console of nay router and ping another end router. First of all, we need to configure the Network Interfaces on both of the Routers. Go to the global configuration mode and enter the following commands:. Now, we will configure the GRE tunnel interface. It is always recommended to provide a different subnet for both the peer ends. On router R1, I configured tunnel interface and IP address Along with the IP address, you also need to configure local and remote public IP addresses as well. Now, we need to configure a static route for the Peer LAN subnet. We need to define the tunnel interface as an exit interface for the destination network. Just, go to router global configuration mode and run the following command. Now, we have finished the configuration between both the GRE Neighbors. Now, we will initiate a ping for the Router R1 and verify our configuration. If your configuration is perfect, you will receive the ping response messages. R1 ping Did you enjoyed this article? If you are facing any issue during GRE Tunnel configuration, please leave a comment in comment box! Nice blog. I understood the concept very well. This blog is very informative. Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. Table of Contents. Leave a Reply Cancel reply Your email address will not be published.

GRE Tunnel Keepalives


Tunneling provides a mechanism to transport packets of one protocol within another protocol. The protocol that is carried is called as the passenger protocol, and the protocol that is used for carrying the passenger protocol is called as the transport protocol. Generic Routing Encapsulation GRE is one of the available tunneling mechanisms which uses IP as the transport protocol and can be used for carrying many different passenger protocols. The tunnels behave as virtual point-to-point links that have two endpoints identified by the tunnel source and tunnel destination addresses at each endpoint. The below diagram shows encapsulation process of GRE packet as it traversers the router and enters the tunnel interface:. Configuring a GRE tunnel involves creating a tunnel interface, which is a logical interface. Then you must configure the tunnel endpoints for the tunnel interface. The below example explain about how to create simple GRE tunnels between endpoints and the necessary steps to create and verify the GRE tunnel between the two networks. R1's and R2's Internal subnets Both Tunnel interfaces are part of the Since GRE is an encapsulating protocol, we adjust the maximum transfer unit mtu to bytes and maximum segment size mss to bytes. A setting of is a common practice and will ensure unnecessary packet fragmentation is kept to a minimum. After configuring tunnel,two tunnel endpoints can see each other can verify using an icmp echo from one end. Workstations on either network will still not be able to reach the other side unless a routing is configure on each router. Here We will configure static route on both router. Now both networks Good overview. Do you need to configure static routes or is dynamic routing OSPF sufficient for the tunnel to operate? Yes,you can also use dynamic routing ,Only endpoint should be reachable i. Dynamic routing and tunnels combination can be a dangerous. You need to be careful when using a dynamic routing protocol bcoz it cause a GRE tunnel to avoid the recursive routing error message, which brings down the tunnel. This happens because the routers need to have a good path through the network to carry the tunnel to its destination. Make sure that the routers never get confused and think that the best path to the tunnel destination is through the tunnel itself. Thanks for this, but i want to ask, in your example, the internet ip addresses used, would one have to get them off an isp or one can just pick up any one? I can ping the tunnel source and destination addresses and the tunnel seems to be up, but I can't ping the endpoints I checked all configs and compared them to another working tunnel, maybe someone has an idea?

How to configure GRE Tunnel between Cisco Routers

Note : GRE keepalives are not supported together with IPsec tunnel protection under any circumstances. This document discusses this issue. A GRE tunnel is a logical interface on a Cisco router that provides a way to encapsulate passenger packets inside a transport protocol. It is an architecture designed to provide the services in order to implement a point-to-point encapsulation scheme. GRE tunnels are designed to be completely stateless. This means that each tunnel endpoint does not keep any information about the state or availability of the remote tunnel endpoint. A consequence of this is that the local tunnel endpoint router does not have the ability to bring the line protocol of the GRE Tunnel interface down if the remote end of the tunnel is unreachable. The ability to mark an interface as down when the remote end of the link is not available is used in order to remove any routes specifically static routes in the routing table that use that interface as the outbound interface. Specifically, if the line protocol for an interface is changed to down, then any static routes that point out that interface are removed from the routing table. This allows for the installation of an alternate floating static route or for Policy Based Routing PBR in order to select an alternate next-hop or interface. Normally, a GRE Tunnel interface comes up as soon as it is configured and it stays up as long as there is a valid tunnel source address or interface which is up. The tunnel destination IP address must also be routable. This is true even if the other side of the tunnel has not been configured. This means that a static route or PBR forwarding of packets via the GRE tunnel interface remains in effect even though the GRE tunnel packets do not reach the other end of the tunnel. Before GRE keepalives were implemented, there were only ways to determine local issues on the router and no way to determine problems in the intervening network. For example, the case in which the GRE tunneled packets are successfully forwarded, but are lost before they reach the other end of the tunnel. Such scenarios would cause data packets that go through the GRE tunnel to be "black holed", even though an alternate route that uses PBR or a floating static route via another interface might be available. Keepalives on the GRE tunnel interface are used in order to solve this issue in the same way as keepalives are used on physical interfaces. The GRE tunnel keepalive mechanism is similar to PPP keepalives in that it gives the ability for one side to originate and receive keepalive packets to and from a remote router even if the remote router does not support GRE keepalives. Here is an example of a keepalive packet that originates from Router A and is destined for Router B.

How to configure GRE Tunnel between Cisco Routers -- Gre tunnel configuration in gns3



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