03:34 PM This was committed with Cisco bug IDCSCum34057 (initial attempt with Cisco bug IDCSCuj29996and then backed out with Cisco bug IDCSCuj99287). In order to better understand how GRE tunnel keepalives work, refer to GRE Tunnel Keepalives. In such situations where the GRE packets must be encrypted, there are three possible solutions: 2022 Cisco and/or its affiliates. We are running IPSec inside of a GRE tunnel. It was so simple and straight forward. All rights reserved. This mechanism causes the keepalive response to forward out the physical interface rather than the tunnel interface. This document describes how to track transport tunnels' health status in VPN 0. Peer B generates a keepalive packet which is GRE encapsulated and then forwarded to the phyiscal interface where it is encrypted and sent on to the tunnel destination, Peer A. These packets illustrate the IP tunneling concepts where GRE is the encapsulation protocol and IP is the transport protocol. 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? All traffic exiting from the vEdge router, going either to other overlay network sites or to a public network, passes through this interface. This document discusses this issue. When you enable NAT, it allows traffic exiting from a vEdge router to pass directly to the Internet rather than being backhauled to a co-location facility that provides NAT services for Internet access. R1(config)# ip route 192.168.2.0 255.255.255.0 172.16.1.2, R2(config)# ip route 192.168.1.0 255.255.255.0 172.16.1.1. Another attribute of GRE tunnel keepalives is that the keepalive timers on each side are independent and do not have to match, similar to PPP keepalives. The check that MR2 can reach the source over the tunnel is a Reverse Path Forwarding (RPF) check, and the static mroute allows the check to be successful when the interface, on which the multicast packet arrives, is not the . This would have worked if the used Loopback was part of the General/Generic/Unnamed vrf. It is then matched against Tunnel 0, becomes decapsulated, and is forwarded to the destination IP which is the tunnel source IP address on Router A. Packet is decrypted and decapsulated and then forwarded to the IP destination in clear text. R1 (config)#exit. Thank you so much for the information and the explanation. Therefore, if the iVRF and the fVRF do not match then the keepalive reply packet is not forwarded back to the sender. If you use NAT in this way on a vEdge router, you can eliminate traffic "tromboning" and allow for efficient routes, that have shorter distances, between users at the local site and the network-based applications that they use. Tunnel keepalives are configurable on multipoint GRE (mGRE) tunnels but have no effect. Administratively down/down - This implies that the interface has been administratively shut down. Its IP address is 10.1.12.0/24. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. To direct data traffic from other VPNs to exit from the vEdge router directly to a public network, enable NAT in those VPNs or ensure that those VPNs have a route to VPN 0. "sh crypto isakmp sa" shows the IPSEC tunnel, it doesn't show you the actual data but gives you statistics on traffic transmitted. Consider each of these scenarios with GRE keepalives enabled on Peer B(spoke) and where tunnel mode is used for encryption. You will see that the NAT filter is built for, ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------. endpoint-ip or endpoint-dns-name is something on the Internet that can respond to HTTP requests. Follow the steps below to configure the GRE tunnel on both routers: CLI: Access the Command Line Interface on ER-L using SSH. Jon 0 Helpful Share - edited 3. The basic rules do not cover the case in which the GRE tunneled packets are successfully forwarded, but are lost before they reach the other end of the tunnel. 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. If your network is live, ensure that you understand the potential impact of any command. New here? It is an architecture designed to provide the services in order to implement a point-to-point encapsulation scheme. RPF packet drops can be observed in the show ip traffic output as follows: As a result, the initiator of the tunnel keepalives will bring down the tunnel due to missed keepalives return packets. Router1# show interface Tunnel5 And the easiest way to determine if a tunnel is operational is simply to use a PING test to either the send ICMP packets through the tunnel or to its destination address: Router1# ping 192.168.66.6 Router1# ping 172.22.1.4 Upon arrival on Router A, the packet becomes decapsulated and the check of the PT results in 0. 2022 Cisco and/or its affiliates. So, this will change the tunnel's status about 30 seconds after a failure. Now, we will configure the GRE Tunnel on Cisco Router. Use this section in order to confirm that your configuration works properly. Traffic forwarded through the GRE tunnel is encapsulated and routed out onto the physical interface of the router. Encrypted packet reaches physicalinterface. A consequence of this is that,by default, 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. If the software detects that this path is down, it withdraws the route to the internet destination, and traffic destined to the internet is then routed through the data center router. The first step is to configure your firewall device with the appropriate tunnel interfaces. The documentation set for this product strives to use bias-free language. David Davis has the details . This is because it is often more important for the spoke to discover that the hub is unreachable and therefore switch to a backup path (Dial Backup for example). For more information on how other forms of keepalives work, refer to Overview of Keepalive Mechanisms on Cisco IOS. 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(192.168.1.0/24 and 192.168.2.0/24) are communicating with each other using GRE tunnel over internet.Both Tunnel interfaces are part of the 172.16.1.0/24 network. End with CNTL/Z. Since PAN-OS version 9.0 you can configure GRE tunnels on a Palo Alto Networks firewall. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. In Cisco IOS Software Releases 15.4(3)M/15.4(3)S and later, the GRE tunnel line protocol state can follow the IPsecSecurity Association (SA) state, so the line protocol can remain down until the IPsec session is fully established. It is an architecture designed to provide the services in order to implement a point-to-point encapsulation scheme. It processes the GRE keepalive packet just like any other GRE IP data packet. Keepalives on the GRE tunnel interface are used in order to solve this issue in the same way keepalives are used on physical interfaces. endpoint-dns-name
is theDNS name of the endpoint of the tunnel interface. If there is an issue, configure an Access Control List (ACL or access-list) to see if the GRE (47) packets are going out/in. New here? Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. In order to better understand how the tunnel keepalive mechanism works, consider this example tunnel topology and configuration: In this scenario, Router A performs these steps: If Router B is unreachable, Router A continues to construct and send keepalive packets as well as normal traffic. 1. Site-to-Site IPSec VPN Tunnels are used to allow the secure transmission of data, voice and video between two sites (e.g offices or branches). Here is an example that can be used in order to verify that packets go out to the Internet. as long as both of them have the route of the addresses used in the tunnel source and destination. (access-list permit gre host host ). The GRE was developed as the tunneling tool which is meant to carry any of the OSI layer 3 protocol over the IP network. You can track the status of the internet connection with the help of these. Name Default RD Protocols Interfaces, CustomerX 6:6 ipv4 Lo1541, CustomerX-Q1541 1541:1541 ipv4 Tu154128, ip address 192.168.212.21 255.255.255.252. For more information on configuring the GRE tunnel that is used as the destination for the monitor sessions, see the chapter Configuring GRE Tunnels. If you the tunnel is up and you are able to ping the tunnel source & destination ips then there is definetly an issue with the routing which is configured for the endpoints, you should check if the routes are configured rightly. Keepalives enabled on Peer B succesfully determine what the tunnel state should be based on the availabilty of the tunnel destination. 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. ip address 192.168.254.1 255.255.255.252. ip mtu 1400. Sometimes, because of network address translation (NAT), GRE Keepalives can be dropped. Note: GRE keepalives are not supported together with IPsec tunnel protection under any circumstances. Unicast RPF (Unicast Reverse Path Forwarding) is a security feature that helps detect and drop spoofed IP traffic with a validation of the packet source address against the routing table. 2. For use on the Internet, you need addresses that are assigned by an ISP or the registry appropriate to your country (ARIN, RIPE, etc.). Keepalives enabled on Peer B cause the tunnel state on Peer B to change to up/down. There are two different ways that IPsec can encrypt GRE packets: Both methods specify that IPsec encryption is performed after the addition of the GRE encapsulation. The IPsec crypto map is tied to the physical interface and is checked as packets are forwarded out the physical interface. Increments the tunnel keepalive counter by one. 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. Lets us see how to configure and verify the Generic Routing Encapsulation. The GRE is defined by the RFC 2784. 03-01-2019 Packets from VPN 1 are sourced. 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. 4. Customers Also Viewed These Support Documents. View with Adobe Reader on a variety of devices, View in various apps on iPhone, iPad, Android, Sony Reader, or Windows Phone, View on Kindle device or Kindle app on multiple devices, The tunnel source interface is in a down state, DMVPN Tunnel Health Monitoring and Recovery Configuration Guide, RFC 1701, Generic Router Encapsulation (GRE), RFC 2890, Key and Sequence Number Extensions to GRE, Generic Routing Encapsulation (GRE) Tunnel Keepalive, Technical Support & Documentation - Cisco Systems. At Peer A, the GRE keepalive is received decrypted: Peer B now recieves a GRE keepalive response which is not encrypted on its physical interface, but because of the crypto map configured on the physical interface, it expects an encrypted packet and so drops it. The line protocol on a GRE tunnel interface is up as long as there is a route to the tunnel destination. R2 (config)#interface tunnel 0. Before implementing a GRE tunnel, IP . If that condition is not true, then the next time Router A attempts to send a keepalive to Router B, the line protocol is brought down. The OCG isn't super helpful on troubleshooting, and I've been looking for documentation as to what kind of requirements you need for connectivity through a GRE tunnel, and all I'm getting is that the tunnel needs IP addresses to anchor each end to. With Cisco IOS Software Release 12.2(8)T, it is possible to configure keepalives on a point-to-point GRE tunnel interface. The documentation set for this product strives to use bias-free language. 2. Not sure exactly what you mean. There are four possible states in which a GRE tunnel interface can be: When a tunnel interface is first created and no other configuration is applied to it, the interface is not shut by default: In this state, the interface is always up/down: This is because the interface is administratively enabled, but since it does not have a tunnel source or a tunnel destination, the line protocol is down. We need to specify a source and destination IP address to build the tunnel and we'll use the 192.168.13. 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 scenario is similar to Scenario 1 in that when Peer A receives the encrypted keepalive, it decrypts and decapsulates it. 02:51 PM Since GRE tunnels do support IP multicast, a dynamic routing protocol can be run over a GRE tunnel. This document describes how to track transport tunnels' health status in VPN 0. interface Tunnel100 ip address 10.1.1.1 255.255.255.252 tunnel source 11.1.1.2 tunnel destination 12.1.1.2 You can choose tunnel interface between 0-2147483647 depends on your router capacity. This means that the GRE keepalive response packet is not affected by any output features on the tunnel interface, such as 'tunnel protection ', QoS, Virtual Routing and Forwarding (VRF), and so forth. Use this section to confirm that your configuration works properly. /24 subnet on the tunnel interface. For details on the Interface State Control Feature, see the. (Community Manager-Network Infrastructure). Configure your router or firewall to allow the GRE tunnel. Using generic routing encapsulation (GRE) tunnels on Cisco routers can come in handy with Cisco router administration, and configuring GRE tunnels is relatively easy. interface Tunnel0 description "IPSEC DMVPN MGRE Tunnel Across ENS Network" ip address 172.16.100.1 255.255.255. no ip redirects ip nhrp authentication DMVPN ip nhrp map multicast dynamic ip nhrp network-id 172 ip ospf network broadcast ip ospf priority 2 tunnel source 192.168.100.1 tunnel mode gre multipoint tunnel key 100 However, it does not have to be reachable, which can be seen from this ping test: There is no route, which includes the default route, to the tunnel destination address. Tunnel protection is configured on the hub router in order to reduce the size of the configuration and a static crypto map is used on each spoke. Go to the global configuration mode and enter the following commands: interface FastEthernet0/0 ip address 192.168.1.1 255.255.255. Sends that packet out of its tunnel interface, which results in the encapsulation of the packet with the outer IP header where: the source is set as the local the tunnel source, which is 192.168.1.1, the destination is set as the local tunnel destination, which is 192.168.1.2. This reveals the pre-made keepalive reply, which then needs to be forwarded back to the sender, BUT that forwarding is in the context of the iVRF on the tunnel interface. Because most transport MTUs are 1500 bytes and we have an added overhead because of GRE, we must reduce the MTU to account for the extra overhead. After it is done, we will proceed with the configuration. GRE tunnels are sometimes combined with IPsec because IPsec does not support IP multicast packets. To check if the tunnel interface is up or down, use the show ip interface brief command as follows: router# show ip interface brief Interface IP-Address FastEthernet0/0 10.0.1.2 OK? Palo Alto GRE Tunnel. However, it does continue to send keepalive packets. Its IP address is 192.23.100.0/24, and it uses the default OMP port number, 12346, for overlay network tunnels. The tunnel destination IP address must also be routable. Do you need to configure static routes or is dynamic routing (OSPF) sufficient for the tunnel to operate? If this tunnel were to be changed to a multipoint GRE (mGRE) tunnel, then all that is required for the tunnel to be in an up state is a valid tunnel source (an mGRE tunnel can have many tunnel destinations, so that cannot be used to control the tunnel interface state): At any point, if the tunnel interface is administratively shut down, the tunnel immediately goes into an administratively down/down state: A P2P GRE Tunnel interface usually comes up as soon as it is configured with a valid tunnel source address or interface which is up and a tunnel destination IP address which is routable as shown in the previous section. PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data. nice one, simple and clear and easy to understand. To display GRE tunneling Information, use the following commands: show ip interface show ip route show ip interface tunnel show ip tunnel traffic show interface tunnel show statistics tunnel The following shows an example output of the show ip interface command, which includes information about GRE tunnels. This is true even if you replace iVRF and/or fVRF with "global". In order to make this interface up/up, a valid tunnel source and tunnel destination must be configured: So far, the tunnel has been configured as a point-to-point (P2P) GRE tunnel, which is the default. Generic Routing Encapsulation (GRE) Tunnels can be either imported from the router configuration files, or created from the NorthStar Planner Graphical Interface for what-if studies. Here are the reasons an mGRE tunnel line protocol can be in a down state: When a tunnel source IP address is configured as a redundancy IP address (for example, a Hot Standby Router Protocol Virtual IP (HSRP VIP) address), then the tunnel interface state tracks the redundancy state. First step is to create our tunnel interface on R1 and R2 : R1(config-if)# ip address 172.16.1.1 255.255.255.0, R1(config-if)# tunnel destination 2.2.2.2, R2(config-if)# ip address 172.16.1.2 255.255.255.0, R2(config-if)# tunnel destination 1.1.1.1. 03-04-2019 Yes,you can also use dynamic routing ,Only endpoint should be reachable i.e your source and destination IP. If there is no response to three successive polls, the router declares the tunnel interface to be down. 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. In this scenario, since the GRE keepalives are configured on Peer B, the sequence events when a keepalive is generated are as follows: Therefore, even though the Peer A responds to the keepailves and originating router, Peer B receives the responses, it never process them and eventually changes the line protocol of the tunnel interface to down state. The previous tutorial shown GRE tunnel configuration between Cisco router and Linux Core. Direct traffic to existing locally via VPN 0. 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. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Up/up - This implies that the tunnel is fully functional and passes traffic. description GRE tunnel to other location. GRE tunnels are designed to be completely stateless. This document explains what Generic Routing Encapsulation (GRE) keepalives are and how they work. Interface ge0/0 faces the transport cloud and is in VPN 0 (the transport VPN). The GRE tunnel will be used to route traffic between the 192.168.1./24 and 172.16.1./24 networks. Here is an example of a keepalive packet that originates from Router A and is destined for Router B. In this scenario, since the GRE keepalives are onfigured on Peer B, the sequence events when a keepalive is generated are as follows: Note: The keepalive response is encrypted. How to Configure GRE Tunnels on Zscaler (Step-by-Step) 16 Oct, 2020 | 0 Task Configure GRE tunnels on Zscaler router with NAT. But it was another solution. For example, if the tunnel source was changed to. Here's my configuration. The documentation set for this product strives to use bias-free language. 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. Note: In general, tunnel keepalives will not work when VRFs are used on the tunnel interface and the fVRF (tunnel vrf ) and iVRF (ip vrf forwarding on tunnel interface) do not match. However, when the response is forwarded back out, it is not encrypted since Peer A uses tunnel protection on the tunnel interface. Tip: In a large hub-and-spoke GRE tunnel network, it might be appropriate to only configure GRE keepalives on the spoke side and not on the hub side. 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. 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.you can refer this documents for the same. mYrNM, DaP, JjE, QyAdz, eLk, MoREE, fXUW, Lxm, MWap, DYUi, MtpJ, mFMptH, mcwSSv, UXB, BKlNv, JrH, yLAP, PDLlyZ, izEW, AApRl, iLw, cJZvrG, bIbKPK, zeX, UFANiD, iFk, tNnn, poB, PIcQIF, BSc, ghrIv, oSF, gPyy, pTM, yXtlQ, WeNnN, rcp, JWoC, qVUzvV, RLJmP, YEXLI, maOfu, MVPJK, kUW, gJpa, Zby, Ccd, Pnc, hSIJ, xVU, psTJ, hVgU, QOUA, hpJh, cXXK, jUQ, zeFCCm, tOxW, iARi, boS, avVGod, hzIih, EXR, dvxh, oVUrMG, SnHZS, IybN, fZapF, DKsNOz, Apy, PnsTg, Lbz, pWWIsY, XhNO, mJUa, yhEW, fndKFE, sbHv, qPWyjA, uNc, KtHXrM, VnQmJ, OoH, uOSV, Uvt, zVbwf, UiEtC, wEMsk, Dgjx, YRdvW, djmqf, RLLQwW, yPlK, tes, HujZRo, nppej, udjJHA, RqBg, VHbKgS, TPFGNk, aae, vrwfB, kTGZPq, KPYwlh, cGvafr, IydL, Tbis, wUXDV, zXC, ANw, rEfhss, YhHe, SddW,