GNS3 Topology: BGP Split-Horizon Rule and Route Reflector

hi
BGP Split-Horizon Rule and Route Reflector





PART I


PART II

GNS3 Topology: BGP Next-Hop Rule on Different Medias

Next-Hop

GNS3 Topology: BGP Synchronization Rule

BGP Synchronization

GNS3 Topology: BGP Rules ebgp-multihop configuration

hi again

GNS3 Topology: Layer 3 VPNs Over Multipoint L2TPv3 Tunnels

VPN services have been traditionally deployed over IP core networks by configuring MPLS or through L2TPv3 tunnels using point-to-point links. This feature introduces the capability to deploy layer 3 VPN services by configuring multipoint L2TPv3 tunnels over an existing IP core network. This feature is configured on only the PE routers and requires no configuration on the core routers. The L2TPv3 multipoint tunnel network allows layer 3 VPN services to be carried through the core without the configuration of MPLS. 

Border Gateway Protocol (BGP) is used to advertise the tunnel endpoints and the subaddress family indentifier (SAFI) specific attributes (which contains the tunnel type, and tunnel capabilities). This feature introduces the tunnel SAFI and the BGP SAFI-Specific Attribute (SSA) attribute. The tunnel SAFI defines the tunnel endpoint and carries the endpoint IPv4 address and next hop. The tunnel SAFI is identified by the SAFI number 64. The BGP SSA carries the BGP preference and BGP flags. It also carries the tunnel cookie, tunnel cookie length, and session ID. The BGP SSA is identified by attribute number 19. 

These attributes allow BGP to distribute tunnel encapsulation information between PE routers. VPNv4 traffic is routed through these tunnels. The next hop, advertised in BGP VPNv4 updates, determines which tunnel to use for routing tunnel traffic.

(2008,MPLS VPN over L2TPv3 Tunnels, retrieved from http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/cs_l3vpn.html, February 2011)



PART 1



PART 2



you can find this topology here

GNS3 Topology: Inter Provider MPLS VPN (Back to Back VRF Method)

Inter-Provider VPN feature allows the VPN information to be redistributed between adjacent MPLS VPN entities so that client sites belonging to customer which is dispersed across multiple service provider backbones can communicate with each other.

To maintain the continuity of VPN services across multiple service providers, there are four different options to distribute VPNv4 information across the ASBR routers:

1- Back-to-Back VRF Method
2- Multiprotocol eBGP for VPNv4
3- Multi-hop MP-eBGP between Route-Reflectors
4- Non-VPN transit provider


In this approach, ASBRs are interconnected either via a single link consisting of logical subinterfaces or via multiple physical links. VRFs are configured on the ASBRs to collect VPN client routes. Each subinterface or interface connected between the ASBRs is dedicated to a single client VRF. The single client VRF can run eBGP, RIPv2, EIGRP, OSPF, or static routing to distribute the VPN routes to its adjacent peer.

"Lobo L, Lakshman U, 2005, MPLS Configuration on Cisco IOS Software, Cisco Press"

PART 1 (enabling MPLS and PE-PE routing configuration inside SP 1)



PART 2 (enabling MPLS and PE-PE routing configuration inside SP 2)



PART 3 (Configuring VRF instances and PE-CE routing configuration)



PART 4 (Verification of VPN)

GNS3 Topology: MPLS VPN Hub and Spoke Topology Configuration

In certain circumstances, it may be desirable to use a hub-and-spoke topology so that all spoke sites send all their traffic toward a central site location. It can be achieved across MPLS VPN.

All traffic from the spoke sites, destined either for the central site services or for intersite connectivity, will flow via the central hub site. With this type of topology, the spoke sites export their routes to the hub site, and then the hub site re-exports the spoke site routes through a second interface (either physical or logical) using a different route target so that other spoke sites can import the routes. This causes the hub site to become a transit point for interspoke connectivity. (Guichard J, Pepelnjak I, 2001, MPLS and VPN Architectures, Cisco Press)

Here is the HUB and SPOKE MPLS VPN configuration. (this topology and configuration was taken from the book "MPLS Configuration On Cisco IOS Software"

PART 1



PART 2

GNS3 Topology: MPLS VPN (BGP PE-CE Routing)

In an MPLS VPN network, BGP attributes for a VPN site are transparently transported across the service provider backbone to another site in the same VPN. Because there is a single routing protocol used across the VPN between service provider core and customer sites, the concept of redistribution does not apply.

BGP PE-CE peering in an MPLS VPN environment can be performed in two different ways:

1-) BGP PE-CE VPN sites implementing unique AS numbers (in our example, CUSTOMER A between Site 1 and Site 2)

2-) BGP PE-CE VPN sites implementing same AS numbers   (in our example, CUSTOMER B between Site 1 and Site 2)

There will be no issue when implementing BGP PE-CE routing for customers which use unique AS in both VPN sites. However, using same AS number in both VPN sites causes an issue because of the BGP loop prevention mechanism. if both sites have same AS number, routing updates from one site would be dropped at the other site; therefore, connectivity cannot be established between the sites without additional configuration on PE routers.  ("neighbor XX.XX.XX.XX as-override" under bgp address-family configuration)

here is the configuration of MPLS VPN with BGP PE-CE Routing.

PART 1



PART 2

GNS3 Topology: Basic iBGP and eBGP Configuration

PART 1

Actually, in this first part of the video, there is nothing about BGP Configuration, rather I tried to prepare my topology for BGP lab. But I wanted to put this video into the blog, because it still shows how to configure frame relay switch in GNS3, and Putty CM.



PART 2



PART 3