At the first and before we go, I assume that everyone about to participate with us in this lab has at least the basic knowledge in the following topics:
*BGP in general:
BGP overview & BGP Study Notes.
* Route Reflectors.
* OSPF network point-to-point.
*Redistribution and propagation of IPv4 and VPNv4 prefixes/routes inside and outside the MPLS cloud.
*MPLS overview.

LAB overview:
– We have an ISP “MPLS” cloud uses BGP to propagate IPv4 and VPNv4 routes between PEs [Provider Edges] and uses the OSPF as IGP to forward traffic.
– ISP MPLS cloud consists of the following routers:
1- RR “act as a route reflector”.
2- PE1 and PE2 connected to VPN customers “vrf test”.
3- PE3 “act as an Internet gateway and connected to the Internet “another ISP [GW]”.
4- Core1 the heart of the network which is the traffic forwarding machine and connected to all PEs and RR, also it should be free from BGP only runs OSPF.

Routers Loopback addresses:

• RR: 172.193.50.125/32
• PE1:172.193.50.1/32
• PE2:172.193.50.2/32
• PE3:172.193.50.3/32
• Core1:172.193.50.110/32
• GW:4.4.4.2/32

Interfaces on Core1 router:

interface FastEthernet0/0
ip address 172.16.125.2 255.255.255.252
!
interface FastEthernet1/0
ip address 172.16.1.2 255.255.255.252
!
interface FastEthernet2/0
ip address 172.16.2.2 255.255.255.252
!
interface FastEthernet3/0
ip address 172.16.3.2 255.255.255.252

Check List:

1. Check the LDP neighbors on Core1 router.
2. Check the OSPF neighbors on Core1 router and be sure that no DR elections are taking place.
3. Check the BGP sessions of IPv4 and VPNv4 on all routers starting from the route reflector.
4. Check the vrf test routing table on both PE1 and PE2.”if not receiving routes check the root cause”
5. ping from CE-1 to CE-2 and vice-versa “check the reason if not successful”
6. Check the EBGP session between PE3 and GW.
7. ping the network propagated by GW to our network: 100.100.100.100/32 “check the reason if not successful”
8. Be sure that the Router ID’s and the core network are only propagated by OSPF but the customers “IPv4 and VPNv4” are propagated by BGP.

Note: All routers are Cisco 3600 series with IOS: c3640-js-mz124-25a.bin

the previous checklist would refresh the head and will allow us to find the root cause of any problem happens, so after check I am waiting your feedbacks here in comments or on my mail: osama@blog.experit.org

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