DMVPN - Tag - Fryguy's Blog

DMVPN and Routing Protocols – CDP

Fryguy — Sun, 07 Aug 2011 13:39:28 +0000

This post will build off my last one, DMVPN, and here we will discuss the routing protocol options as well as each of their configurations. This is more of a Why? What? Eh? type of post – hence the picture. Here I will show how to use CDP for a routing protocol – yes, CDP.

Right from the Cisco kool-aid website: On-Demand Routing (ODR) is an enhancement to Cisco Discovery Protocol (CDP), a protocol used to discover other Cisco devices on either broadcast or non-broadcast media. With the help of CDP, it is possible to find the device type, the IP address, the Cisco IOS® version running on the neighbor Cisco device, the capabilities of the neighbor device, and so on. In Cisco IOS software release 11.2, ODR was added to CDP to advertise the connected IP prefix of a stub router via CDP. This feature takes an extra five bytes for each network or subnet, four bytes for the IP address, and one byte to advertise the subnet mask along with the IP. ODR is able to carry Variable Length Subnet Mask (VLSM) information.

In order to get this lab to work I had to tweak a few configs on the routers, namely I had to remove the 0/0 route I had pointing to the ISP and make it a more specific – 150.0.0.0/8 pointing to the “ISP” router as the next hop. With ODR only a default route (0/0) is passed from the hub to the spokes, so no other default route can exist.

Quick note: When I am posting the configurations for the sites I will only notate the routing protocol additions. If you need information on DMVPN configuration, see my previous post.

DMVPN and Routing Protocols – BGP

Fryguy — Sat, 06 Aug 2011 21:52:31 +0000

This post will build off my last one, DMVPN, and here we will discuss the routing protocol options as well as each of their configurations. I will break out each protocol into a separate post in order to help keep things straight, putting them all together has the potential to get confusing (for both you and me!). The routing protocol options I will document are OSPF, RIPv2, EIGRP, and BGP and each has some unique features and quirks, so I will try and point them out where necessary. The only problem that BGP introduces here is that it is a bit higher-touch for routing. You will need to configure the spoke as well as the HUB to support the new neighbor relationship. This might not be a big deal, but if you have quite a few of these sites, this means every add will require you to modify the hub router. Guess we could call it job security 🙂 Quick note: When I am posting the configurations for the sites I will only notate the routing protocol additions. If you need information on DMVPN configuration, see my previous post. Router/Switch Output Commands Notes Lets start with the DMVPN hub. First, lets get that loopoback created so we have something to advertise. Rack1DMVPN(config)#interface Loopback0 Rack1DMVPN(config-if)# ip address 100.100.100.100 255.255.255.255

DMVPN and Routing Protocols – RIP

Fryguy — Fri, 05 Aug 2011 12:46:07 +0000

This post will build off my last one, DMVPN, and here we will discuss the routing protocol options as well as each of their configurations. I will break out each protocol into a separate post in order to help keep things straight, putting them all together has the potential to get confusing (for both you and me!). The routing protocol options I will document are OSPF, RIPv2, EIGRP, and BGP and each has some unique features and quirks, so I will try and point them out where necessary. One of the joys of RIPv2 in a DMVPN network is Split-Horizon. Just a quick refersher on Split Horizon – it is the rule that prohibits a router from advertising a route through an interface that the router itself uses to reach the destination. This is done in order to prevent loops in the network, but with DMVPN we need to disable this feature via the no split-horizon command. Quick note: When I am posting the configurations for the sites I will only notate the routing protocol additions. If you need information on DMVPN configuration, see my previous post. Router/Switch Output Commands Notes First up, the DMVPN hub.

DMVPN and Routing Protocols – EIGRP

Fryguy — Fri, 05 Aug 2011 12:12:03 +0000

This post will build off my last one, DMVPN, and here we will discuss the routing protocol options as well as each of their configurations. I will break out each protocol into a separate post in order to help keep things straight, putting them all together has the potential to get confusing (for both you and me!). The routing protocol options I will document are OSPF, RIPv2, EIGRP, and BGP and each has some unique features and quirks, so I will try and point them out where necessary.
One of the joys of EIGRP in a DMVPN network is Split-Horizon. Just a quick refresher on Split Horizon – it is the rule that prohibits a router from advertising a route through an interface that the router itself uses to reach the destination. This is done in order to prevent loops in the network, but with DMVPN we need to disable this feature via the no split-horizon EIGRP AS# command.
Quick note: When I am posting the configurations for the sites I will only notate the routing protocol additions. If you need information on DMVPN configuration, see my previous post.
Router/Switch Output
Commands
Notes
First up, the DMVPN hub:
First thing we should do is create a loopback interface and address so we have something to see and ping.
Rack1DMVPN(config)# int l0
Rack1DMVPN(config-if)# ip address 100.100.100.100 255.255.255.255

DMVPN and Routing Protocols – OSPF

Fryguy — Thu, 04 Aug 2011 13:43:09 +0000

This post will build off my last one, DMVPN, and here we will discuss the routing protocol options as well as each of their configurations. I will break out each protocol into a separate post in order to help keep things straight, putting them all together has the potential to get confusing (for both you and me!). The routing protocol options I will document are OSPF, RIPv2, EIGRP, and BGP and each has some unique features and quirks, so I will try and point them out where necessary.
Quick note: When I am posting the configurations for the sites I will only notate the routing protocol additions. If you need information on DMVPN configuration, see my previous post.
Router/Switch Output
Commands
Notes
OSPF
What one needs to keep in mind here is that mGRE is a non-broadcast multi-access network (NBMA) how OSPF works. In order for OSPF to operate properly, the DMVPN hub router must be the OSPF DR and all the other routers should not be allowed to be a DR/BDR. The only way you could have a DR/BDR design if this was a multi-hub DMVPN network – and that is beyond the scope of this post (due to hardware limitation in my lab). Also, the mGRE tunnel on the hub router must be set to a OSPF broadcast network via the ip ospf network broadcast command.
So, let’s get on with the configuration – DMVPN Hub first.

DMVPN

Fryguy — Wed, 03 Aug 2011 12:53:03 +0000

So let me talk a moment and talk about DMVPN – Dynamic Multipoint VPN technology.
Currently I am working on a project to test the viability of a DMVPN network as well as help bring the team up to speed on this technology. Since I am doing that I figured it would be a good idea to share some of what I have learned with others – plus blogging it like this helps me to review the material at a later date. 🙄
So the first thing that probably should be answered – What is DMVPN? It is a solution for building a scalable IPsec VPN network utilizing the Internet (or other public network – say MPLS) for the WAN backbone. DMVPN takes advantage of another protocol, Next Hop Resolution Protocol (NHRP) and a Multipoint GRE tunnel interface. With NHRP the router will query the Next Hop Server (NHS) to find out a mapping for a network. Once it finds out the remote IP, the Multipoint GRE will build a dynamic tunnel between the two routers. It will then place that network in its NHRP mapping table.
DMVPN can provide a full-mesh topology with a simplified configuration. You only need to have all the spokes communicate with the hub initially, and then from there the spokes can learn the outside IP of the other routers and build dynamic tunnels when they need to communicate. What is nice with this is that if you add a new spoke to the network, there are neither changes on the hub nor any other spoke – only the new spoke needs to be configured.
What are some of the uses for DMVPN? Work at home workers, remote working locations via cellular, backup to a private WAN, and those are just to name a few. I am sure you can come up with some of you own based on your experiences. (continued)