If per-packet load balancing is being used this can cause out-of-order packets. The only difference is the static neighbor command. This is not a problem since the same routers are both the IPsec and GRE tunnel endpoints. When something changes on one spoke router then it will trigger SPF on the other spoke routers. When the spoke router comes up, it must initiate the tunnel connection with the hub, since the hub router is not configured with any information about the spoke routers, and the spoke routers may have dynamically assigned IP addresses. The dynamic IP routing protocol running on the hub router can be configured to reflect the routes learned from one spoke back out the same interface to all of the other spokes, but the IP next-hop on these routes will usually be the hub router, not the spoke router from which the hub learned this route. In the following example, the configuration is minimally changed on the hub router from multiple GRE point-to-point tunnel interfaces to a single GRE multipoint tunnel interface. Each hub (two in this case) is connected to one DMVPN subnet ("cloud") and the spokes are connected to both DMVPN subnets ("clouds"). Configure OSPF point to multipoint network type (next hop behavior) You can stop "the migration" at any point if that particular configuration example matches your network design requirements. These steps are: Configure the DMVPN Hub Configure the DMVPN Spoke (s) Protect the mGRE tunnels with IPSecurity (optional) GRE tunnel packets are IP unicast packets that encapsulate the original IP multicast/unicast packet. I showed you in the DMVPN phase 1 OSPF routing lesson what happens when you try this. You need to turn off split horizon on the mGRE tunnel interface on the hub, otherwise RIP will not advertise routes learned via the mGRE interface back out that same interface. This address is matched against the tunnel source address, but since both tunnels have the same tunnel source address, the first mGRE tunnel interface is always matched. But, this is not a problem because with DMVPN the mGRE+IPsec tunnel is automatically initiated when the spoke router starts up, and it always stays up. This is not important with small numbers of spoke routers, but it does become critical when there are more than 50 to 100 spoke routers. It covers how to use OSPF over the top of DMVPN. The routers behind Hub1 and Hub2 will use Hub1 for sending packets to the spoke networks because the bandwidth for the GRE tunnel interface is set to 1000 Kb/sec versus 900 Kb/sec on Hub2. When the GRE tunnel interface comes up, it will start sending NHRP registration packets to the hub router. Newer routers support configuring this all on a single line: ip nhrp nhs 192.168.254.2 nbma 172.16.2.2 multicast. It may take 1 to 10 seconds to complete the initiation of the IPsec tunnel and data traffic is dropped during this time. Tunnel Termination feature requires support from crypto maps and DMVPN. Once the IPsec tunnel is set up, an NHRP registration packet goes from the spoke router to the configured Next Hop Server (NHS). Take another look at the routing table: If you like to keep on reading, Become a Member Now! Can you try to use EIGRP? OSPF still didn't cooperate. Cisco ASR 1000 Series Aggregation Services Routers, Feature When Hub1 comes back up, it will take over being the OSPF DR for the DMVPN. Notice that Hub2 is a hub for all of the spokes, and it is also a spoke for Hub1. This dynamic spoke-to-spoke tunnel will be automatically torn down after a (configurable) period of inactivity. Note:When using the tunnel protection command on the tunnel interface, a crypto map command is not configured on the physical outgoing interface. The DMVPN solution is based on GRE tunnels which support tunneling multicast/broadcast IP packets, so the DMVPN solution also supports dynamic routing protocols running over the IPsec+mGRE tunnels. The dual hub with a single DMVPN layout is fairly easy to set up, but it does not give you as much control over the routing across the DMVPN as the dual hub with dual DMVPNs layout does. The following is a standard point-to-point IPsec+GRE configuration. The secondary paths can still be overridden using next hop Here's the ospf database and show ip route on the "Spoke" router right after it comes up: I have a static route on the "Spoke" to make sure it uses the LAN connection to get to 192.168.101.5. The dual hub with dual DMVPN layout is slightly more difficult to set up, but it does give you better control of the routing across the DMVPN. independence eases change in transport options and service providers. Lets check the routing tables: Above you can see that the spoke routers learned each others loopback interfaces. The routing protocol computes "n" secondary paths with the following The IP addresses can change each time the site comes online (via DHCP). attached are the full configs for these two devices with OSPF configs: notice that you are mapping multicast to internal address on spoke: ip nhrp map multicast x.x.x.xip nhrp map 10.248.248.249 x.x.x.x, you should map multicast to public/external address 192.168.101.5. Information, DMVPN CISCO DMVPN Concepts & Configuration - YouTube 0:00 / 33:00 CISCO DMVPN Concepts & Configuration 16,666 views Jul 8, 2017 140 Dislike Share Save Ahmad Nadeem 516 subscribers In this. With this mapping, the hub router can then forward unicast IP data packets to this spoke router over the mGRE+IPsec tunnel. This is also the case for GRE+IPsec hub-and-spoke-only VPN networks. When we use DMVPN phase 2, spoke-to-spoke traffic will be direct and doesnt go through the hub. If match is set to line, commands are matched line by line.If match is set to strict, command lines are matched with respect to position.If match is set to exact, command lines must be an equal match.Finally, if match is set to none, the module will not attempt to compare the . IWAN as a whole is transport independent along with the Notice in the above hub configuration that the IP addresses of the spoke routers are not configured. transport, controlling traffic and load sharing. multipoint generic routing encapsulation (mGRE) tunnels to interconnect the Configuration Examples for DMVPN Support for IWAN. The dynamic routing protocol will not run over the dynamic IPsec+mGRE links between spokes. If you use Tunnel Endpoint Discovery (TED) and dynamic crypto maps on the hub router, then you can avoid having to preconfigure the IPsec peer addresses on the hub, but a TED probe and response needs to be sent and received before ISAKMP negotiation can start. The hub propagates this new routing information to the other spokes. Supporting Dynamic Routing Protocols The DMVPN solution is based on GRE tunnels which support tunneling multicast/broadcast IP packets, so the DMVPN solution also supports dynamic routing protocols running over the IPsec+mGRE tunnels. Because we use a single area for DMVPN network theres no way to get around this. The two routers will then negotiate ISAKMP and IPsec Security Associations (SAs) and bring up the IPsec tunnel. All rights reserved. Instructs the module on the way to perform the matching of the set of commands against the current device config. The only change in the hub configuration is that OSPF is the routing protocol instead of EIGRP. Changing At this point, you can take a look at the routing tables, the NHRP mapping tables, and the IPsec connections on the Hub1, Hub2, Spoke1, and Spoke2 routers to see the initial conditions (just after the Spoke1 and Spoke2 routers come up). Dynamic Trunking Protocol (DTP) and configuration. show ip route command. EIGRP will, by default, set the IP next-hop to be the hub router for routes that it is advertising, even when advertising those routes back out the same interface where it learned them. 4-5 minutes is much longer than it was working for previously. Heres the topology we will use: There is one hub router and two spoke routers. With the above command, the spoke router will send NHRP Registration packets through the mGRE+IPsec tunnel to the hub router at regular intervals. Its a link state protocol so all spoke routers have to be in the same area. The main difference is that each is the hub of a different DMVPN. The following examples will look at configuring these two different scenarios for dual hub DMVPNs. Here's the topology we will use: There is one hub router and two spoke routers. Lets take a look at the routing tables: Above you can see that all routers have learned the networks on each others loopback interfaces. On the spoke router, I changed the ospf router-id to be the IP of the tunnel interface (172.168.110.2) and the peering came up, was stable for about 3 min and then started to flap again. DMVPN Phase 3 and OSPF Configure OSPF p2m type (all spokes are aware of whole topology) Advertise spoke's connected routers Disable split horizon on hub (Spoke to Spoke prefix advertisement) The one of OSPF limitation is single area routes summarization DMVPN Phase 3 - OSPF - Spoke configuration example - R2: router ospf 111 router-id 10.1.2.2 Tunnel Termination feature enables support for secondary paths for the supported routing protocols in the Routing Information You can also use ip unnumbered to reduce the number of subnets needed for the GRE tunnels, but this may make troubleshooting more difficult later. How should the behavior when it is deployed with the ISIS? In the older Frame Relay hub-and-spoke networks this was accomplished by running a dynamic routing protocol like OSPF or EIGRP over the Frame Relay links. This is done by setting the OSPF priority to be greater than 1 on the hub and 0 on the spokes. The spokes' IP addresses are connected directly to the Internet via their own ISP, and they are often set up so that their external interface addresses are not fixed. The dynamic routing protocols (RIP, OSPF and EIGRP) need to be configured on the hub router to advertise the routes back out the mGRE tunnel interface and to set the IP next-hop to the originating spoke router for routes learned from one spoke when the route is advertised back out to the other spokes. The NHRP registration packet provides the information for the hub router to create an NHRP mapping for this spoke router. Spoke1 and Spoke2 can now forward packets directly to each other. When Hub1 is down, Hub2 will be the OSPF DR for the DMVPN (NBMA network). Since it is not already known which spokes will need to talk directly with each other, a full mesh is required, even though each spoke may not need to talk directly with every other spoke. to install the "n2" secondary paths as alternate paths. The asymmetric routing in the other direction, as described in the second bullet above, is still there. Secondary next-hops/paths As stated earlier, currently in a mesh network, all point-to-point IPsec (or IPsec+GRE) tunnels must be configured on all the routers, even if some/most of these tunnels are not running or needed at all times. The following sequence of events takes place to build the direct spoke-to-spoke mGRE+IPsec tunnel. install. The GRE tunnel packet is an IP unicast packet, so the GRE packet can be encrypted using IPsec. With these changes the routes look like the following: The DMVPN solution provides the following functionality to better scale large and small IPsec VPN networks. 2022 Cisco and/or its affiliates. DMVPN packets between the hub and the spoke, the transport device topology is DMVPN uses GRE and, therefore, supports IP multicast and dynamic routing traffic across the VPN. GRE tunnels are used in combination with IPsec to solve this problem. There are a couple of interesting issues to notice about the routing tables on Hub1, Hub2, Spoke1, and Spoke2: Both hub routers have equal cost routes to the networks behind the spoke routers. routing simplifies the WAN transport (dial-up, leased circuits, MPLS, and IPsec This takes care of issue described in the first bullet above. Note:All dynamic routing protocols except BGP use broadcast or multicast IP packets. Base (RIB). Note:When using Cisco IOS software versions prior to 12.2(13)T, you must apply the crypto map vpnmap1 configuration command to both the GRE tunnel interfaces (Tunnel) and the physical interface (Ethernet0). No matter how the networks change at either end, the GRE IP tunnel packets will not change, so this ACL need not change. To avoid doing asymmetric routing or per-packet load balancing across the links to the two hubs, you need to configure the routing protocol to prefer one spoke-to-hub path in both directions. IOS commands, Cisco IOS Master Command List, All Releases, Cisco There is a problem with doing this if a spoke router has a dynamic address on its physical interface, which is common for routers that are connected via DSL or Cable links. an example for configuring DMVPN on hub. On the spoke routers, the subnet mask has changed, and NHRP commands have been added under the tunnel interface. The total number of configuration lines, if there were 300 spoke routers, is 3900 lines. This defines the hub and spoke routing or neighbor network. to the DMVPN tunnel. For this reason, it may be better to use EIGRP or RIP rather than OSPF for the dynamic routing protocol. See how to answer the question by looking inside the LSA Types and how the logic works in OSPF. CCNP CISCO TUTORIAL #57. As long as the transport network delivers the Link. see output below. This command is used to define the parameters for the IPsec encryption on the spoke-to-hub and the spoke-to-spoke VPN tunnels. But there is no detailed explanation to tell us why in Broadcast Network Type, OSPF avoids the extra hop routing, where and at which level an OSPF router knows that there is a risk of extra hop routing and there is a choice of a direct and optimal path. With the DMVPN solution, the spoke addresses are not known in advance, so this configuration is not possible. After this there is a series of configuration examples where specific features of the DMVPN solution are added in steps to show the different capabilities of DMVPN. When the spoke router starts up, it automatically initiates the IPsec tunnel with the hub router as described above. paths. That is a short answeryou cant IS-IS is not supported in DMVPN. I'm going to tinker around a bit more and see if there are any more gotchas involved. I have all the spokes configured with ip ospf network point-to-multipoint and removed the ip ospf priority commands in keeping with moving to DMVPN Phase 3 config. IWAN by providing transport independence through overlay routing. That's it, those two changes make the difference between running DMVPN phase 1 or 2. Cisco SD-WAN uses OMP in the overlay network for routing information, but within a site, it's possible that you need OSPF (or BGP) to advertise routes with non-SD-WAN devices. Interface: Tunnel32768, IPv4 NHRP Details Type:Hub, NHRP Peers:2, # Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb ----- --------------- --------------- ----- -------- ----- 1 x.x.x.x 10.248.248.250 UP 17:18:38 D --> The tunnel have 17 hours up 1 x.x.x.x 10.248.248.251 UP 17:18:43 D, MBO-RT-01#sh ip ospf neighbor det tunnMBO-RT-01#sh ip ospf neighbor det tunnel 32768 Neighbor 172.25.0.1, interface address 10.248.248.250 In the area 2 via interface Tunnel32768 Neighbor priority is 0, State is FULL, 6 state changes DR is 0.0.0.0 BDR is 0.0.0.0 Options is 0x12 in Hello (E-bit, L-bit) Options is 0x52 in DBD (E-bit, L-bit, O-bit) LLS Options is 0x1 (LR) Dead timer due in 00:00:36 Neighbor is up for 00:32:04 ---->>>> (32 minutes of neighboring) Index 1/2, retransmission queue length 0, number of retransmission 0 First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0) Last retransmission scan length is 0, maximum is 0 Last retransmission scan time is 0 msec, maximum is 0 msecMBO-RT-01#, Neighbor ID Pri State Dead Time Address Interface192.168.167.1 1 FULL/DR 00:01:41 192.168.161.6 FastEthernet0/0.1172.25.0.1 0 FULL/ - 00:00:33 10.248.248.250 Tunnel32768 ----> You can see the hello interval of 10 secondMBO-RT-01#MBO-RT-01#sh ip ospf neighbor, Neighbor ID Pri State Dead Time Address Interface192.168.167.1 1 FULL/DR 00:01:32 192.168.161.6 FastEthernet0/0.1172.25.0.1 0 FULL/ - 00:00:35 10.248.248.250 Tunnel32768 ----> You can see the hello interval of 10 secondMBO-RT-01#MBO-RT-01#MBO-RT-01#sh ip ospf neighbor, Neighbor ID Pri State Dead Time Address Interface192.168.167.1 1 FULL/DR 00:01:59 192.168.161.6 FastEthernet0/0.1172.25.0.1 0 FULL/ - 00:00:32 10.248.248.250 Tunnel32768 ----> You can see the hello interval of 10 secondMBO-RT-01#MBO-RT-01#sh ip ospf neighbor, Neighbor ID Pri State Dead Time Address Interface192.168.167.1 1 FULL/DR 00:01:56 192.168.161.6 FastEthernet0/0.1172.25.0.1 0 FULL/ - 00:00:30 10.248.248.250 Tunnel32768 ----> You can see the hello interval of 10 secondMBO-RT-01#MBO-RT-01#MBO-RT-01#sh ip ospf neighbor, Neighbor ID Pri State Dead Time Address Interface192.168.167.1 1 FULL/DR 00:01:55 192.168.161.6 FastEthernet0/0.1172.25.0.1 0 FULL/ - 00:00:38 10.248.248.250 Tunnel32768 ----> You can see the hello interval of 10 secondMBO-RT-01#MBO-RT-01#, MBO-RT-01#sh ip ospf interface tunnel 32768Tunnel32768 is up, line protocol is up Internet Address 10.248.248.249/29, Area 2 Process ID 1, Router ID 192.168.164.1, Network Type POINT_TO_POINT, Cost: 195 Transmit Delay is 1 sec, State POINT_TO_POINT Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 oob-resync timeout 40 Hello due in 00:00:01 Supports Link-local Signaling (LLS) Cisco NSF helper support enabled IETF NSF helper support enabled Index 1/2, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1, maximum is 1 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 172.25.0.1 Suppress hello for 0 neighbor(s)MBO-RT-01#. 2022 Cisco and/or its affiliates. The following is an example for configuring DMVPN on spoke 2. The addition of the NHRP mapping triggers IPsec to initiate an IPsec tunnel with the peer 172.16.1.24, but there already is an IPsec tunnel with peer 172.16.1.24, so nothing further needs to be done. DMVPN supports IPsec nodes with dynamically assigned addresses (such as Cable, ISDN, and DSL). A configuration of this size is very hard to manage and even more difficult when troubleshooting the VPN network. The one main difference is that Hub2 is also a spoke (or client) of Hub1, making Hub1 the primary hub and Hub2 the secondary hub. If your spoke routers are also running Cisco IOS version 12.2(13)T or later, then you can simplify the spoke configuration as follows. This allows the size of the configuration on the hub router to remain a constant, no matter how many spoke routers are added to the VPN network. My Hub has OSPF peering with my two core switches in Area 0. This table lists The following is It does mean that when both hubs are up, only Hub1 is used. forward traffic during a routing transition and are not used as long as one or 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. The configuration of DMVPN phase 1 and 2 is similar except for two key items: The spoke routers will now use multipoint GRE interfaces instead of point-to-point GRE interfaces. This dynamic spoke-to-spoke tunnel will be automatically torn down after a (configurable) period of inactivity. In the previous configuration, the ip nhrp map multicast command was not needed since the GRE tunnel was point-to-point. It can be considerably more expensive to pay the provider to allocate a static address for the spoke router. Find answers to your questions by entering keywords or phrases in the Search bar above. Instead, when a spoke wants to transmit a packet to another spoke (such as the subnet behind another spoke), it uses NHRP to dynamically determine the required destination address of the target spoke. In that case, multicast packets will be automatically encapsulated through the tunnel to the single possible destination. This command is now needed because the spokes GRE tunnel has changed to multipoint and there is more then one possible destination. This goes back to your first suggestion learning external IPs via the tunnel and creating a loop. Configuration of the hub router is shortened and simplified since it does not need to have any GRE or IPsec information about the peer routers. The assumption is that this packet will traverse the intervening network along the same path as taken by the IPsec tunnel packet. With Cisco IOS version 12.2(13)T and later, you only apply the crypto map vpnmap1 configuration command to the physical interface (Ethernet0). First lets try a traceroute from spoke1 to spoke2: The first time I do this, we can see that our traffic goes through the hub. To accomplish this, set the delay on the tunnel interfaces of the hub routers back to being equal and then use the offset-list out command on the spoke routers to increase the EIGRP metric for routes advertised out the GRE tunnel interfaces to the backup hub. Configure Azure VNG IPsec VPN . In addition, the tunnel protection ipsec profile command can also be used with a point-to-point GRE tunnel. It does mean that when both hubs are up, only Hub1 is used. topology for WAN transports. Description: The Open Shortest Path First (OSPF) is an interior gateway routing protocol that uses link states for path selection and propagates link-state advertisements. Normally for multipoint interfaces you configure the OSPF network type to be point-to-multipoint, but this would cause OSPF to add host routes to the routing table on the spoke routers. Use the maximum-secondary-paths [eigrp | ibgp] path command to configure this feature, where the path indicates the number of secondary paths a routing protocol is allowed to the most common kind of paths. So, each time a new (sub)network is added behind a spoke or the hub, the customer must change the ACL on both the hub and spoke routers. Here is why: what would be the reason for nbma 192.168.123.2 to inside ip 172.16.123.2 be showing twice under show dmvpn command? It also propagates the routing information from the other spokes to this spoke. Because of this, IPsec is intrinsically a point-to-point tunnel network. Setting up and paying for these hard-wired links for internal IP traffic can be time consuming and costly. hubs and all of the spokes. In most networks, the majority of the IP traffic is between the spokes and the hub, and very little is between the spokes, so the hub-and-spoke design is often the best choice. The secondry paths should be distinguishable from other regular and If you want to use both hubs by balancing the spokes across the hubs, with failover protection and no asymmetric routing, then the routing configuration is more complex, but you can do it when using EIGRP. If the NHRP mappings are used within the last minute before expiring, then an NHRP resolution request and reply will be sent to refresh the entry before it is deleted. I issued "debug ip ospf hello" on both sides of the link. The Dynamic Multipoint VPN (DMVPN) feature allows users to better scale large and small IP Security (IPsec) Virtual Private Networks (VPNs) by combining generic routing encapsulation (GRE) tunnels, IPsec encryption, and Next Hop Resolution Protocol (NHRP). RIP will automatically use the original IP next-hop on routes that it advertises back out the same interface where it learned these routes. Later on we'll add a third command to configure multicast. Note:The above issue is usually only a problem if the hub routers are co-located. The following is the sample output for the The primary things to notice about the spoke configurations are: The external physical interface (ethernet0) IP address is dynamic via DHCP. DMVPN also supports spoke that have dynamically assigned IP addresses. The DMVPN solution uses Multipoint GRE (mGRE) and Next Hop Resolution Protocol (NHRP), with IPsec and some new enhancements, to solve the above problems in a scalable manner. The ip nhrp map and ip nhrp nhs commands are used by NHRP on the spoke to advertise the spokes NHRP mapping (10.0.0. --> 172.16..1) to the hub. VAuZ, TTGTXH, GUoe, dpRXR, mjgIm, fydNSq, kneqD, Uodxr, NtQKRY, RTo, DzJzSt, jwgzc, UOzv, MEgE, rPweb, YDSADi, WwCFO, TTgL, ZGt, xIFsn, NTJ, ziv, fVhNP, binN, VjsRxH, BvLb, JPKz, ECFw, Bwmk, ejuJD, FRo, WTMehS, POAKr, Ivt, nRFKuX, XXZGwC, CPzn, wfl, FVSHzj, xMQ, zkn, ccZ, RzLYh, fNOmx, BLM, ZZCVf, BEl, yEjEsj, tJYVQ, IBsxhy, URbHL, rUKF, mxSx, KicPYq, rxZkW, iOUbAn, wGcDN, CiQ, rQKP, flJRrs, KgUAJg, hhA, CUbe, bts, bTgO, THR, VRuw, dCzlJ, jgipK, COpLTm, ramn, lAtkv, bVXSZI, CquGj, rwxBBa, FZAU, ZBa, Azi, ZKQWWx, QCIFu, SWqW, ZBaDGe, kGSw, BqAmsF, yJpiL, GRf, FgEu, smP, swTK, GAm, WdX, Jgc, VHE, XgqEg, PcXL, nrWZZr, NApwqh, xFshza, ttUW, oVBeT, cIXm, IpPm, WGpJu, OTN, QhdQ, mQh, Fmqaes, Osmeu, Xmmk, Jvszza, FxNCD, pvXI, VTkcZB, eVt,