For our gre tunnel configuration example, we will use the below topology and the given ip addresses. Feb 27, 2017 ccna gre tunnel configuration and testing with gns3 and wireshark pass your 200125 exam duration. Configuring generic routing encapsulationgre tunnel ip. In order to eliminate gre altogether, you can change the tunnel mode to ipsec. Wan connections and technologies explained configuring singlehomed external bgp for the ccna cloud services and easy virtual network for the ccna snmp v1, v2c and v3 on cisco devices explained.
Pointtopoint generic routing encapsulation gre tunnels. Gre tunneling is accomplished through tunnel endpoints that encapsulate or deencapsulate traffic. Virtual private networks washington university in st. Oct 15, 2014 gre vpn tunnel overview in this packet tracer 6. Basic ipsec vpn topologies and configurations example 32 provides the con. Developed by cisco systems that can encapsulate a wide variety of network layer protocols inside virtual pointtopoint links over an internet protocol network. The device at one end of a vpn tunnel takes an ip packet, encrypts it making it unreadable, and then sends the encrypted packet after encapsulating it in a new ip header.
In the first section of the tutorial below, learn the basics of ipsec and ssl vpns and how they are deployed, or skip to other sections in the vpn tutorial using the table of contents below. The hub router is configured with three separate tunnel interfaces, one for each spoke. In this way, a continue reading gre over ip vpn tunnel in packet tracer. Ipsec over gre configuration and explanation ccie notes. Table 192 on page 195 lists the parameter values that will be used in the. With gre we can easily create a virtual link between routers and allow them to be directly connected, even if they physically arent. Generic routing encapsulation gre page 5 configuration example figure 4.
Virtual tunnel interface vti a virtual tunnel interface has similar characteristic s to any other interface on the device. You can also use a firewall filter to deencapsulate gre traffic on. Gre encapsulates the original ip packet with a new ip header also appending an additional gre header. In the event that it is not, treat it like any other interface. For example, on the procurve secure router, a gre tunnel can. Gre tunnel tutorial on cisco devices understand how to configure generic routing encapsulation gre tunnels for your ccna. The tunnels behave as virtual pointtopoint links that have two endpoints identified by the tunnel source and tunnel destination addresses at each endpoint. In this confgiuration example, we will see how to configure cisco gre generic routing encapsulation tunnel with packet tracer.
Generic routing encapsulation gre provides a private, secure path for transporting packets through an otherwise public network by encapsulating or tunneling the packets. Configuring gre tunnel through a cisco asa firewall in this configuration tutorial i will show you how to configure a gre tunnel between two cisco ios routers. This gre tunnel is encapsulated in an ipsec tunnel at device ipsecl. Gre does not include strong security to protect its payload. This provides a mechanism for organizations to connect users and offices together, without the high costs of dedicated leased lines. Ensure you can ping the ip addresses that you configured on the tunnel interface. Vpn tunnels allow geographically separate private local area networks to be connected to each other across public wide area networks. Gre stands for generic routing encapsulation, and it is an extremely simple form of tunneling.
A gre tunnel creates the illusion of a pointtopoint link between two routers that are otherwise not directly connected to each other. Sep 22, 2016 cisco ccna gre tunnel configuration 1. Each gre tunnel between the hubspoke routers is configured with its unique network id. With gre we can easily create a virtual link between. Generic routing encapsulation gre is a tunneling protocol developed by cisco that allows the encapsulation of a wide variety of network layer protocols inside pointtopoint links a gre tunnel is used when packets need to be sent from one network to another over the internet or an insecure network. Gre generic routing encapsulation is a tunneling protocol that allows us to encapsulate packets into other packets. Reconfigure r1 and r3 so that the tunnel protocol is ipsec.
Gre is a cisco developed protocol which is one of many tunneling protocols. Interface and hardware component configuration guide, cisco ios xe release 3s gre ipv6 tunnels. The goal is that pc1 private network be able to ping pc2 another private network, by going via r3 which represent internet. Contents 6 pointtopoint gre over ipsec design guide ol902301 sizing the branch sites 510 tunnel aggregation and load distribution 511 network layout 511 appendix a scalability test bed configuration files a1 cisco 7200vxr headend configuration a1 cisco catalyst 6500sup2vpnsm headend configuration a2 cisco 7600sup720vpn spa headend configuration p2p gre on sup720 a6. How to configure gre tunnel between cisco and mikrotik routers. Reserved0 bits 112 a receiver must discard a packet where any of bits 15 are nonzero.
Configuring a tunnel with generic routing encapsulation. Configure ipsec on the routers at each end of the tunnel r1 and r3 crypto isakmp policy 10. Generic routing encapsulation gre configuration guide. Configure another loopback interface on router godzilla and nessie. Forwarding decapsulated ipv4 payload packets when a tunnel endpoint decapsulates a gre packet which has an ipv4 packet as the payload, the destination address in the ipv4 payload packet header must be used to forward the packet and the ttl of the payload packet must be decremented. How to configure gre tunnel in cisco router ip with ease. Generic routing encapsulation gre is a tunneling protocol developed by cisco systems that encapsulates a wide variety of network layer protocols inside virtual pointtopoint links over an internet protocol internetwork. How to configure a gre tunnel between a mikrotik router and a cisco router april 23, 2018 april 27, 2018 timigate 2 comments cisco, mikrotik, vpn generic routing encapsulation gre is a tunneling protocol that was developed by cisco to encapsulate a wide variety of protocols transported inside a virtual pointtopoint link. Contents 6 pointtopoint gre over ipsec design guide ol902301 sizing the branch sites 510 tunnel aggregation and load distribution 511 network layout 511 appendix a scalability test bed configuration files a1 cisco 7200vxr headend configuration a1 cisco catalyst 6500sup2vpnsm headend configuration a2 cisco 7600sup720vpn spa headend configuration p2p gre on.
This is caused by the router learning the tunnels destination ip address through the tunnel interface thus recursive look up fails and the tunnel goes down thus dropping the neighbor relationship. For example, you can also transport multicast traffic and ipv6 through a gre tunnel. We can use gre to create tunnels between routers, the tunnels are established with public ip addresses and the ip packets we encapsulate use private ip addresses. Tunnel destination tunnel mode tunnel source anipv4 anipv4address. Dec 07, 2006 originally developed by cisco, generic routing encapsulation gre is now a standard, defined in rfc 1701, rfc 1702, and rfc 2784.
Originally developed by cisco, generic routing encapsulation gre is now a standard, defined in rfc 1701, rfc 1702, and rfc 2784. Tunnel interface configurationbranch dynamic public ip address 214. Overview of ipsec virtual private networks vpns a virtual private network vpn provides a secure tunnel across a public and thus, insecure network. In 2008 free ccna workbook originally started as a sharable pdf but quickly evolved into the largest ccna training lab website on the net. Understanding cisco dynamic multipoint vpn dmvpn, mgre.
In addition, gre tunnels can encapsulate multicast data streams for transmission over the internet. The general specification is described in rfc 1701, and the encapsulation of ip packets over ip is defined in rfc 1702 as a specific implementation of gre. Make sure multicast traffic is passing through the isp network. The gre tunnel is between the west and east routers in ospf area. Later it become industry standard rfc 1701, rfc 2784, rfc 2890. Configuring gre tunnel by r p porwal configuring a gre tunnel involves. Is this loop back not required for gre 2 on tunnel interfaces, we assigned ips 192. In the example shown in figure 192 on page 193, ip packets from the private.
Like as17304a, as23745a uses a single crypto map with two process ids to protect traf. Gre is a tunneling protocol used to transport packets from one. A gre tunnel is a generic routingencapsulation tunnel. Gre permits routing protocols to travel through the tunnel. I am sorry to say that but unless you are able to reserve a single ip address for static nat purposes, establishing the gre tunnel in your current network with pat is most probably not possible. Note that a compliant implementation must accept and process this field. The gre tunnel itself is similar to an ipsec tunnel. Step 6 identify requirement for pfs and reference pfs group in crypto map if necessary. The gre tunnel is between the west and east routers in ospf area 0. Create an ipsec vpn tunnel using packet tracer ccna. Introduction to multipoint gre and nhrp pluralsight.
Configuring device a tunnel destination ip address 2. The routing tables of two routers show that they are directly connected via gre tunnel. Gre is multiprotocol and can tunnel any osi layer 3 protocol. Sitetosite ipsec vpn deployments 107 step 4 identify and assign ipsec peer and any highavailability requirements. Typically youll be required to set up the tunnel interface ips and provide public ip addresses for both ends of the gre tunnel. Norsak on private internet access via l2tp ipsec cisco ios client. The gre connection endpoints are terminated vi a a virtual tunnel interface vti configured in each device. Ip header information and inserts ipsec fields into the packet. The routers at the two ends of a gre tunnel use virtual interfaces, known as tunnel interfaces, in place of serial interfaces used by directly connected routers. Configuring gre tunnel through a cisco asa firewall. As opposed to gre over ipsec, which encrypts anything that is encapsulated by gre, ipsec over gre encrypts only the payload and not the routing protocols running over a. In this vpn tutorial you will learn all about vpn basics, starting with the different types of vpns and ending with a vpn implementation strategy.
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. For example, we can encapsulate an ip packet into another ip packet. You can also test that by using eigrp neighbor command, which allows you to send the routing exchange information between your gre tunnels using unicast traffic. Refer to the router interface summary table at the end of this lab for the correct interface identifiers. Configuring pointtopoint gre vpn tunnels unprotected. Gre offers no security so ipsec must be implementedwith gre for encryption of. We just want to show you this command and let you know that we are configuring a traditional pointtopoint gre. It is used to transport payload of variousprotocols such as ipv4, ipv6 and isis,a linkstate routing protocol.
As opposed to gre over ipsec, which encrypts anything that is encapsulated by gre, ipsec over gre encrypts only the payload and not the routing protocols running over a gre tunnel. Apr 23, 2018 how to configure a gre tunnel between a mikrotik router and a cisco router april 23, 2018 april 27, 2018 timigate 2 comments cisco, mikrotik, vpn generic routing encapsulation gre is a tunneling protocol that was developed by cisco to encapsulate a wide variety of protocols transported inside a virtual pointtopoint link. This type of configuration works well when this is the behavior and there are a limited number of tunnels that need to be configured. While it is a cisco developed protocol, it is also defined in several rfcs 1701, 1702 and 2784. Gre, based on the example configuration shown in figure 192 on page 193. The virtual interfaces on routers at the two ends of a gre tunnel are configured with ip. Im here to help you as much as possible, thats why i try to answer every comment and email that i receive. For example, gre tunnel between the hub and remote office 1 could use network 10. Here is an example of a tunnel set up between two cisco routers. The traditional implementation of a gre tunnel involved the configuration of a pointtopoint tunnel going between two sites. Gre over ip vpn tunnel in packet tracer danscourses.
Tunnel mode encapsulates the original ip packet inside of an ipsec ip packet. With gre, a virtual tunnel is created between the two endpoints cisco routers and packets. Generic routing encapsulation gre techlibrary juniper. Rfc 2784 generic routing encapsulation march 2000 3.
Each mode provides strong protection, but using a slightly different solution. The next command tunnel mode gre ip is in fact not necessary as this is the default setting. Vpn tunnels are now part of the ccna certification exam. When the sending router decides to send a packet into the gre tunnel, it will wrap the whole packet into another ip packet with two headers. The gre tunneling protocol is developed by the cisco system that can encapsulate the wide variety of the network layer protocol inside the point to point links over the internet protocol internetwork. Generic routing encapsulation gre is a tunneling protocol developed by cisco systems that can encapsulate a wide variety of network layer protocols inside virtual pointtopoint links or pointtomultipoint links over an internet protocol network. There are other gre modes like tunnel mode gre multipoint used in dmvpn mentioned in. Routing configuration guide, cisco ios xe everest 16. Cisco ccna gre tunnel configuration asm, rockville, maryland. Configure a gre tunnel between router godzilla and nessie.
Tunnel mode is most frequently used in gatewayt ogateway communication or with a virtual private network vpn. The purge gre resets the gre encapsulation on a switch and also purges all the gre configurations as well as patterns in the nonvolatile storage. Gre tunneling is accomplished by creating routable tunnel. Gre is a tunneling protocol that was originally developed by cisco, and it can do a few more things than ipinip tunneling. 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. Generic routing encapsulation gre is a tunnelling protocol which is used to transport ip packets over a network. As gre does not have its own mechanism to encrypt traffic it depends on ipsec for getting the encryption job done. One of the routers is located behind a cisco asa 5500 firewall, so i will show you also how to pass gre traffic through a cisco asa as well. In this lab, you will configure an unencrypted pointtopoint gre vpn tunnel and verify that network traffic is using the tunnel. Cisco ccna gre tunnel configuration asm, rockville. A gre tunnel is established on a router level and differs depending on the hardware type or service you use.
Gre encapsulation supports any osi layer 3 protocol. Cisco ccna gre tunnel configuration linkedin slideshare. Ccna gre tunnel configuration and testing with gns3 and wireshark pass your 200125 exam duration. Rfc 2784 generic routing encapsulation march 2000 2. You will also configure the ospf routing protocol inside the gre vpn tunnel.
Dont hesitate to contact me or leave a comment under my posts on this website and ill try to address and answer your questions if i. Cisco eigrp is working by sending multicast traffic. You are familiar with the fundamental operation of a virtual private network vpn, and the concept of tunneling by now. Jul 16, 20 as gre does not have its own mechanism to encrypt traffic it depends on ipsec for getting the encryption job done. Dont hesitate to contact me or leave a comment under my posts on this website and ill try to address and answer your questions if i can.
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