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GNS3 BGP EXAMPLES

9/1/2019



 
In our previous blog article we’ve discussed the benefits and the fundamental
principles of BGP/MPLS L3 VPNs. We have covered the definition of the basic
terms such as the Route Distinguisher (RD), the Route Target (RT) and the
VPN-IPv4 prefix. This post goes further. We are going to support the theory
behind the BGP/MPLS L3 VPNs with a practical configuration.

Nov 29, 2008 - Here's a quick demonstration on how to configure two routers to
be BGP neighbors. Now we'll configure BGP on R1 and advertise only the
42.42.42.0/24. To Influence BGP Routing GNS3 Labs:: Cisco Router Simulator. In
this course I will be configuring BGP and various BGP features throughout the
network. Sam expertly teaches the crucial information you’ll need to know to
pass tests, or survive in the real world, no fluff, no one offs, no useless
information. Our courses are designed to get you everything you need to know on
a topic, in 2 hours or less.
Our lab network consists of PE1, PE2 and P routers, which are part of a service
provider’s MPLS network. There are two remote sites: 1 (with CustomerA_Site1 and
CustomerB_Site1) and 2 (with CustomerA_Site2 and CustomerB_Site2) both connected
to a service provider’s MPLS network. Our goal is to interconnect the remote
customer sites so that they can communicate privately over a shared medium. This
is where BGP/MPLS VPNs come in handy, separating traffic from both customers,
using a combination of the VRF, MPLS and MP-BGP.
The customers use private addresses inside their routing domains, which overlap
each other. For instance, both customers use the same prefix 172.16.1.0/24 for
site 1 and 172.16.2.0/24 for site 2.
Picture 1: Network Topology

IGP CONFIGURATION ON P AND PE ROUTERS

First, we will configure the IGP protocol among all P and PE routers to support
LDP and BGP adjacencies within the provider network. Even IGP or static routes
might be a choice. We can configure EIGRP, as all routers in our example are
from Cisco.

EBGP CONFIGURATION ON CUSTOMER ROUTERS

Now let’s configure the eBGP adjacency between CE and PE routers. BGP AS numbers
at each customer site must be unique and differ from the provider’s ASN. For
instance, the customer A BGP AS number is 64401 at site 1 and ASN 64402 at site
2. We also advertise each customers’ subnet from CE to PE router with the
following network commands:

CONFIGURING MP-BGP ON PE ROUTERS

Multiprotocol BGP is explained in RFC 4760. It defines the extensions to BGP-4
to enable it to carry the routing information for multiple Network Layer
protocols (e.g., IPv6, L3VPN). Therefore, we will configure the MP-BGP to
distribute customers’ prefixes. The extensions are backward compatible. A router
that supports the extensions can interoperate with a router that doesn’t support
the extensions.
iBGP neigborship is formed between the PE routers, using ASN 64501. No BGP is
configured on router P.

Note: The command neighbor 10.1.1.3 send-community extended is automatically
configured under the address-family vpnv4 section.

Note: The command neighbor 10.1.1.1 send-community extended is automatically
configured under the address-family vpnv4 section.

ENABLE MPLS ON PE AND P ROUTERS

We need to enable MPLS in a provider’s network. Customers’ data are then
switched in the MPLS network based on the outer (LSP) label. We will enable MPLS
on a provider’s P router and on PE routers.

CREATE AND ASSIGN VRFS

Customers’ forwarding tables are separated by using the VPN routing and
forwarding table (VRF) concept on the PE router. One VRF is configured on the PE
router for each customer. The Router’s PE interface that connects CE router to
provider’s MPLS network is then assigned to the customer VRF.
Route distinguisher is added on the PE router to customer’s prefix to
distinguish the same prefix and mask in a different VRF. For instance, PE1
router announces prefixes RD1:172.16.10/24 and RD2:172.16.1.0/24 along with VPN
label to PE2 router inside the BGP update message. The RD is used to distinguish
the prefixes and it has no impact how the routes are installed into the VRFs.
The route target is an extended community attribute used for the import/export
of VPN routes. For instance, a VPN prefix 172.16.1.0/24 sent from PE1 to PE2
inside of the MP-BGP update message and carrying the route-target 64501:1 is
imported into VRF Customer A on PE2.

Note: the commands route-target export 64501:1 and route-target import 64501:1
are automatically configured under vrf configuration.

Note: the commands route-target export 64501:2 and route-target import 64501:2
are automatically configured under vrf configuration.

Now we need to assign L3 interfaces to customer VRF.
We will create the same VRFs on PE2 and assign interfaces to VRFs.

CONFIGURE EBGP TOWARDS CUSTOMERS ON THE PE ROUTERS

So far, we have configured eBGP on the customers’ routers. However, we also need
to define the BGP neighbors for the PE routers under address-family ipv4 vrf
section, in order to establish the BGP adjacencies with the CE routers.

INSPECTING THE FORWARDING PLANE

Picture 2 depicts the captured traffic on the link between the PE1 and P
routers, while pinging from PC1A to PC2B. The outer MPLS label Switching Path
(LSP) is 18 and is used for label switching. It is learned via the LDP (Label
Distribution Protocol) and has a local significance.
Picture 2: Captured Traffic Between PE1 and P Routers
MPLS forwarding table of PE1 is depicted in Picture 3.
Picture 3: MPLS Forwarding Table of PE1 Router
The label 21 is the inner (VPN) label, added by the PE1 router. It is used to
identify the correct next-hop (10.0.0.18) on the PE2 router for Customer A data
traffic. The inner label is kept untouched by the P router. Only the PE routers
perform either push or pop of the VPN labels. The VPN label for Customer B
traffic is 22.
The P router is a transit router that performs pop of LSP labels 18 and 19
(Picture 4). This router takes the forwarding decision solely based on labels.
The label 19 is the LSP label pushed on packet by PE2 router when sending
traffic to 10.1.1.1.
Picture 4: MPLS Forwarding Table of P Router
Picture 5 depicts the captured traffic on the link between P and PE2 routers,
while issuing the ping command from PC1A to PC2B. There is only one MPLS header
with VPN label 21 because the P router has poped the label 18. Router PE2
removes the inner VPN header 21 and forwards ICMP request as a plain IP packet
to CE2A (10.0.0.18).
Picture 5: Captured Traffic Between P and PE2 Routers
In the opposite direction, a packet carrying ICMP echo reply message from PC2A
to PC1A contains the LSP label in the MPLS header. The VPN label is the same as
in echo request (21) because both sides are customer A. Picture 6 depicts MPLS
forwarding table of PE2 router.
Picture 6: MPLS Forwarding Table of PE2 Router

Picture 7 depicts a forwarding table of the PE2 router for VRF Customer A. It
contains two routes learned via BGP. It is the route 172.16.2.0/24 announced by
customer router CE2A and the route 172.16.1.0 advertised by the router PE1.
Picture 7: VRF of Customer A on PE2 Router

INSPECTING CONTROL PLANE

BGP Update message sent from PE1 to PE2 is depicted in Picture 8. Notice, that
there is only one MPLS header with LSP label 18, VPN label is missing. It
ensures that MP-BGP message is sent via the MPLS network. VPN label is
distributed inside the MP-BGP update message along with the unique VPN-IPv4
prefix.
Picture 8: BGP Update Message with LSP label 18
VPN-IPv4 route is a customer’s route that is modified to be unique in order to
use the same private IP address for customers. VPN-IPv4 routes consists of the
Route Distinguisher (RD) and the prefix. Picture 9 shows the content of the NLRI
inside the MP_REACH_NLRI path attribute. It is the prefix 172.16.1.0 with the RD
64501:2 and the label stack (VPN label) 22 (Customer B).
Picture 9: Unique VPN-IPv4 Route
The BGP update message also contains the Path attribute – EXTENDED_COMMUNITIES
where the route-target 64501:2 is located. It is shown in Picture 10.
Picture 10: Route Target Inside Extended Community
Conclusion:
We have provided the exact configuration steps that can help our readers create
a BGP/MPLS L3 VPNs and grasp the overall concept. If you need to acquire more
theoretical knowledge about the BGP/MPLS VPNs concept, read our first blog post.


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 * Baixar Pokemon Cristal Shard
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 * Best Helicopters For Private Use India
 * Baixar Pokemon Cristal Shard
 * Sv8100 Pc Pro Download
 * Apricorn Ez Gig
 * P&g Practice Reasoning Test
 * Proteus 8 Professional Licence Key
 * 3ds Max Price
 * One Power Readers Reviews
 * Clearid Torrent File
 * Kknd Krossfire Psx Psp
 * Disney Soundtrack Rar
 * Cheap Security Cameras
 * Kundali Bhagya Episode 67 Full Episode
 * Cara Bermain Rubik 3x3

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