PE-CE Routing

Feb 28 2009

6PE – IPv6 over MPLS

6PE is a really cool feature which allows IPv6 islands to communicate with each other over an MPLS/IPv4 core network. IPv4 addresses space is fast running out so familiarising yourself with IPv6 is probably a good idea.

Consider the toplogy below.

Service providers can leverage their MPLS networks to deliver IPv6 solutions without having to rearchitect their networks. The PE devices are configured with IPv6 routing capability, however the P nodes have no IPv6 routing functionality enabled.

Data packets are encapsualted into MPLS frames on the ingress PE with two labels, the bottom of the stack label being the label assigned to the IPv6 prefix and the top label which is used to forward the packet has a label binding of the PE3s loopback 0 address.

From 6PE2 if we do a cef lookup for the IPv6 prefix connected to 6PE1 we see the following.

6PE2#sh ipv6 cef 2001:2:: 2001:2::/64 nexthop 10.0.0.5 FastEthernet1/0 label 16 19

The bottom of stack label ie 19 is the ipv6 label and can be verified on 6PE2 as below.

6PE2#sh ip bgp ipv6 unicast labels Network Next Hop In label/Out label 2001:2::/64 ::FFFF:1.1.1.1 nolabel/19

The top label ie 16 is generated from a recursive lookup which points to the remote 6PE device ie 6PE1s loopback address.

6PE2#sh ip cef 1.1.1.1 1.1.1.1/32 nexthop 10.0.0.5 FastEthernet1/0 label 16 6PE2#

the 6CEs can use an IPv6 IGP for 6PE-to-6CE connectivity or they can rely on static routing. In this case static routing has been configured as below.

ipv6 route ::/0 FastEthernet1/0 2001:2::2

Watch the video below or download it and watch it on your iPod or iPhone.

By Zarar • BGP, CCIE SP, iPhone, iPod, IPv6, MPLS, PE-CE Routing • 2 • Tags: CCIE SP, IPv6, MPLS

Nov 18 2008

OSPF Sham-Links

OSPF sham-links give the technical administrator an option to use either the back door link or the WAN link by presenting Type 1 LSAs over the WAN cloud. CEs then have Type 1 LSAs via 2 routes and as they are the same type of LSA you can manipulate the cost to either use the back door or the WAN link.

By zismail • CCIE SP, MPLS VPN, OSPF, PE-CE Routing • 0 • Tags: CCIE SP, MPLS VPN, OSPF

Nov 18 2008

MPLS VPN – using Site of Origin (SOO)

When an MPLS VPN customer is dual homed, SOO can be used to prevent routing loops as well as sub optimal routing.

Toplology as below.

Using Site of Origin community with BGP

I’ve used EIGRP between CE1 and CE3 to demonstrate the sub optimal routing.(its only suboptimal if you want to route traffic between sites using the backdoor link, which isnt always the case)

By zismail • CCIE SP, MPLS VPN, PE-CE Routing • 0 • Tags: BGP, CCIE SP, MPLS VPN, PE-CE Routing, SOO

Nov 17 2008

MPLS VPN using BGP as the PE-CE Routing Protocol

Topology is as below.

MPLS VPN using EBGP as the PE-CE routing protocol

By zismail • BGP, CCIE SP, MPLS VPN, PE-CE Routing • 1 • Tags: BGP, MPLS VPN, PE-CE Routing

Nov 17 2008

MPLS VPN using EIGRP as the PE-CE routing Protocol

Topology is as below.

By zismail • CCIE SP, EIGRP, MPLS VPN, PE-CE Routing • 1 • Tags: EIGRP, MPLS VPN, PE-CE Routing

May 23 2008

PE-CE Routing MPLS VPN

PE-CE Routing OSPF – MPLS

Introduction

If you are serious about using OSPF as your PE to CE protocol on the edge of the MPLS cloud then you should familiarise yourself with RFC 4577 (OSPF as the Provider/Customer Edge Protocol for BGP/MPLS IP Virtual Private Networks).

MPLS – PE-CE routing scenario

Starting from the left in the MPLS toplogy below. Rip is redistributed into OSPF on CE1, therefore 10.5.1.0/24 is seen as an external route on the MPLS PE1. 10.4.1.0/24 however is advertised into a non-zero ospf area and is thus recieved at PE1 as an inter-Area route. Both of these routes are advertised across the MPLS cloud by MBGP. MBGP then redistributes these routes into OSPF on PE2. OSPF then advertises these routes across the MPLS PE-CE link to CE2. CE2 sees these routes as follows:-

15.1.1.0/24: External route LSA Type 5
10.4.1.0/24: Summary route LSA Type 3

From the right, CE2 advertises 10.6.1.0/24 to PE2 as an intra-area route ie LSA Type 1/2. PE2 then acts as an ABR for area2 and advertises 10.6.1.0/24 across then MPLS Cloud to PE1. PE1 advertises 10.6.1.0/24 across the PE-CE link to CE1. CE1 sees this route as follows:-

10.6.1.0/24: Summary route LSA Type 3

The Key here is understanding which router acts as an ABR and forwards generates summary routes.

Type 1/2 LSAs ie intra-area routes can be forwarded nativly across the MPLS cloud. However that is outside of the scope of this document and will be covered in a later document.

Topology

Tutorial

Components Used

The topology below was configured on the following software and hardware:-

IOS: c7200-k91p-mz.122-31.SB11.bin:

Hardware: 7200VXR chassis emulated using GNS3 and dynamips.

Configurations

ce1.cfg
pe1.cfg
pe2.cfg
ce2.cfg