MPLS L3 VPN With Allowas-in and AS-Override

 

MPLS L3 VPN

(Allowas-in and AS-Override)

Topology :


Lab kali ini kita memiliki 7 router yang akan dikonfigurasi OSPF, IBGP, EBGP, MPLS.

  •  OSPF Sebagai routing protocol underlay yang akan menghungkan 3 router (PE1, P, PE2).
  •  IBGP sebagai routing protocol yang akan membawa traffic VPNv4 dari PE1 to PE2 via OSPF.
  • EBGP routing protocol sebagai penghubung antar AS 1 dan AS 10 agar antar Customer dapat terkoneksi.
  • MPLS sebagai Overlay yang akan menandai setiap traffic dengan Label LDP (Label distribution protocol) ketika traffic melewati interface yang telah kita konfigurasi sebagai MPLS.

Initial Configuration all router :

P :

hostname P

Int lo0

Ip add 15.15.15.15 255.255.255.255

Int e0/0

ip add 172.0.10.1 255.255.255.0

no shutdown

exit

Int e0/1

ip add 172.0.20.1 255.255.255.0

no shutdown

exit

 

PE1 :

hostname PE1

Int lo0

ip add 10.10.10.10 255.255.255.255

Int e0/0

ip add 172.0.10.2 255.255.255.0

no shutdown

exit

 

PE2 :

hostname PE2

int lo0

Ip add 16.16.16.16 255.255.255.255

int e0/1

ip add 172.0.20.2 255.255.255.0

no shutdown

exit

 

CE17:

hostname CE17

Int lo0

ip add 17.17.17.17 255.255.255.255

exit

Int e0/1

ip add 10.10.1.1 255.255.255.0

no shutdown

exit

 

CE18:

hostname CE18

Int lo0

ip add 18.18.18.18 255.255.255.255

exit

Int e0/2

ip add 10.10.1.2 255.255.255.0

no shutdown

exit

 

CE19:

hostname CE19

Int lo0

ip add 19.19.19.19 255.255.255.255

exit

Int e0/0

ip add 10.10.2.1 255.255.255.0

no shutdown

exit

 

CE20:

hostname CE20

Int lo0

ip add 20.20.20.20 255.255.255.255

exit

Int e0/2

ip add 10.10.2.2 255.255.255.0

no shutdown

exit

 

Configuration IGP and LDP :

P :

Router ospf 10

Network 15.15.15.15 0.0.0.0 area 0

Network 172.0.10.0 0.0.0.3 area 0

Network 172.0.20.0 0.0.0.3 area 0

Int e0/0

mpls ip

Exit

Int e0/1

mpls ip

exit

 

PE1 :

Router ospf 10

Network 10.10.10.10 0.0.0.0 area 0

Network 172.0.10.0 0.0.0.3 area 0

Exit

Int e0/0

mpls ip

exit

 

PE2 :

Router ospf 10

Network 16.16.16.16 0.0.0.0 area 0

Network 172.0.20.0 0.0.0.3 area 0

exit

Int e0/1

mpls ip

exit

 

Configuration VRF on the PE router :

PE1 :

Ip vrf CUS-A

Rd 1:1

Route-target both 1:1

Exit

Ip vrf CUS-B

Rd 2:2

Route-target both 2:2

Int e0/1

Ip vrf forwarding CUS-A

Ip add 10.10.1.254 255.255.255.0

Exit

Int e0/2

Ip vrf forwarding CUS-B

Ip add 10.10.1.254 255.255.255.0

exit

 

PE2 :

Ip vrf CUS-C

Rd 1:1

Route-target both 1:1

exit

Ip vrf CUS-D

Rd 2:2

Route-target both 2:2

exit

Int e0/0

Ip vrf forwarding CUS-A

Ip add 10.10.2.254 255.255.255.0

exit

Int e0/2

Ip vrf forwarding CUS-B

Ip add 10.10.2.254 255.255.255.0

exit

Verify connection on Router PE to CE


Configuration IBGP on Router PE :

PE1 :

Router bgp 1

Network 10.10.10.10 mask 255.255.255.255

Neighbor 16.16.16.16 remote-as 1

Neighbor 16.16.16.16 update-source loopback0

Address-family vpnv4

Neighbor 16.16.16.16 activate

 

PE2 :

Router bgp 1

Network 16.16.16.16 mask 255.255.255.255

Neighbor 10.10.10.10 remote-as 1

Neighbor 10.10.10.10 update-source loopback0

Address-family vpnv4

Neighbor 10.10.10.10 activate

 

Configuration EBGP on PE and CE

CE17 :

Router bgp 10

Network 17.17.17.17 mask 255.255.255.255

Neighbor 10.10.1.254 remote-as 1

exit

 

CE18 :

Router bgp 20

Network 18.18.18.18 mask 255.255.255.255

Neighbor 10.10.1.254 remote-as 1

exit

 

CE19 :

Router bgp 30

Network 19.19.19.19 mask 255.255.255.255

Neighbor 10.10.2.254 remote-as 1

exit

 

CE20 :

Router bgp 40

Network 20.20.20.20 mask 255.255.255.255

Neighbor 10.10.2.254 remote-as 1

exit

 

PE1 :

Router bgp 1

Network 10.10.10.10 mask 255.255.255.255

address-family ipv4 vrf CUS-A

Neighbor 10.10.1.1 remote-as 10

exit-address-family

address-family ipv4 vrf CUS-B

Neighbor 10.10.1.254 remote-as 20

exit

 

PE2 :

Router bgp 1

Network 16.16.16.16 mask 255.255.255.255

address-family ipv4 vrf CUS-C

Neighbor 10.10.2.1 remote-as 30

exit-address-family

address-family ipv4 vrf CUS-D

Neighbor 10.10.2.2 remote-as 40

exit-address-family

exit

 

VERIFICATION :

CE17 :



CE18 :


CE19 :



CE20 :



PE1 :


PE2 :




Test Connection CE to CE

CE17 to CE19 :


CE18 to CE20 :

Hasil dari traceroute di kotak merah gambar diatas bahwa paket dari CE17 dan 18 to CE19 dan CE20 ditandai oleh PE1 sebagai traffic mpls telah berhasil dan traffic paket telah sampai ke CE lain dengan mechanism MP-BGP yang berfungsi untuk share information dari VRF.

 

Configuration all router :

P :

!

hostname P

!

interface Loopback0

 ip address 15.15.15.15 255.255.255.255

!

interface Ethernet0/0

 ip address 172.0.10.1 255.255.255.252

 mpls ip

!

interface Ethernet0/1

 ip address 172.0.20.1 255.255.255.252

 mpls ip

!

router ospf 10

 network 15.15.15.15 0.0.0.0 area 0

 network 172.0.10.0 0.0.0.3 area 0

 network 172.0.20.0 0.0.0.3 area 0

!

end

PE1 :

!

hostname PE1

!

ip vrf CUS-A

 rd 1:1

 route-target export 1:1

 route-target import 1:1

!

ip vrf CUS-B

 rd 2:2

 route-target export 2:2

 route-target import 2:2

!

interface Loopback0

 ip address 10.10.10.10 255.255.255.255

!

interface Ethernet0/0

 ip address 172.0.10.2 255.255.255.252

 mpls ip

!

interface Ethernet0/1

 ip vrf forwarding CUS-A

 ip address 10.10.1.254 255.255.255.0

!

interface Ethernet0/2

 ip vrf forwarding CUS-B

 ip address 10.10.1.254 255.255.255.0

!

router ospf 10

 network 10.10.10.10 0.0.0.0 area 0

 network 172.0.10.0 0.0.0.3 area 0

!

router bgp 1

 bgp log-neighbor-changes

 network 10.10.10.10 mask 255.255.255.255

 neighbor 16.16.16.16 remote-as 1

 neighbor 16.16.16.16 update-source Loopback0

 !

 address-family vpnv4

  neighbor 20.20.20.20 activate

  neighbor 20.20.20.20 send-community extended

 exit-address-family

 !

 address-family ipv4 vrf CUS-A

  neighbor 10.10.1.1 remote-as 10

  neighbor 10.10.1.1 activate

 exit-address-family

 !

 address-family ipv4 vrf CUS-B

  neighbor 10.10.1.2 remote-as 20

  neighbor 10.10.1.2 activate

 exit-address-family

!

end

PE2 :

!

hostname PE2

!

ip vrf CUS-C

 rd 1:1

 route-target export 1:1

 route-target import 1:1

!

ip vrf CUS-D

 rd 2:2

 route-target export 2:2

 route-target import 2:2

!

interface Loopback0

 ip address 16.16.16.16 255.255.255.255

!

interface Ethernet0/0

 ip vrf forwarding CUS-C

 ip address 10.10.2.254 255.255.255.0

!

interface Ethernet0/1

 ip address 172.0.20.2 255.255.255.252

 mpls ip

!

interface Ethernet0/2

 ip vrf forwarding CUS-D

 ip address 10.10.2.254 255.255.255.0

!

router ospf 10

 network 16.16.16.16 0.0.0.0 area 0

 network 172.0.20.0 0.0.0.3 area 0

!

router bgp 1

 bgp log-neighbor-changes

 network 16.16.16.16 mask 255.255.255.255

 neighbor 10.10.10.10 remote-as 1

 neighbor 10.10.10.10 update-source Loopback0

 !

 address-family vpnv4

  neighbor 10.10.10.10 activate

  neighbor 10.10.10.10 send-community extended

 exit-address-family

 !

 address-family ipv4 vrf CUS-C

  neighbor 10.10.2.1 remote-as 30

  neighbor 10.10.2.1 activate

 exit-address-family

 !

 address-family ipv4 vrf CUS-D

  neighbor 10.10.2.2 remote-as 40

  neighbor 10.10.2.2 activate

 exit-address-family

!

end

CE17 :

!

hostname CE17

!

!

interface Loopback0

 ip address 17.17.17.17 255.255.255.255

!

interface Ethernet0/1

 ip address 10.10.1.1 255.255.255.0

!

router bgp 10

 bgp log-neighbor-changes

 network 17.17.17.17 mask 255.255.255.255

 neighbor 10.10.1.254 remote-as 1

!

end

CE18 :

!

hostname CE18

!

!

interface Loopback0

 ip address 18.18.18.18 255.255.255.255

!

interface Ethernet0/2

 ip address 10.10.1.2 255.255.255.0

!

router bgp 10

 bgp log-neighbor-changes

 network 18.18.18.18 mask 255.255.255.255

 neighbor 10.10.1.254 remote-as 1

!

end

CE19 :

!

hostname CE19

!

!

interface Loopback0

 ip address 19.19.19.19 255.255.255.255

!

interface Ethernet0/0

 ip address 10.10.2.1 255.255.255.0

!

router bgp 10

 bgp log-neighbor-changes

 network 19.19.19.19 mask 255.255.255.255

 neighbor 10.10.2.254 remote-as 1

!

end

 

CE20 :

!

hostname CE20

!

!

interface Loopback0

 ip address 20.20.20.20 255.255.255.255

!

interface Ethernet0/2

 ip address 10.10.2.2 255.255.255.0

!

router bgp 10

 bgp log-neighbor-changes

 network 20.20.20.20 mask 255.255.255.255

 neighbor 10.10.1.254 remote-as 1

!

end

 

Thankss

Syawal Adhitya


ALLOWAS-IN

Dengan topoology yang sama, bagaimana jika antar Customer memeiliki AS yang sama, CUS-B dan CUS-D with AS20, by default route tersebut akan di drop jika customer D memilki ASN yang sama, Karena ketika PE1 menerima sebuah packet dari CUS-B packet tersebut akan di tag dengan CUS-B ASN, Output BGP :

CE18# BGP(0): 10.10.1.254 rcv UPDATE about 20.20.20.20/32 -- DENIED due to: ASPATH contains our own AS;

Ada 2 cara untuk resolve probelem ini :

  1. Menggunakan Allow-in command ini direlease untuk memungkinkan BGP di site lain untuk inject update. Feature ini hanya dapat digunakan untuk eBGP Peers.
  2. Menggunakan AS-Override  berfungsi untuk replace ASN Customer dengan menggunakan ASN SP (Service Provider).

Sebelum Configure Allowas-in kita ubah terlebih dahulu CUS-D menjadi AS20 :

CE20 :

no router bgp 10

router bgp 20

network 20.20.20.20 mask 255.255.255.255

neighbor 10.10.2.254 remote-as 1

exit

Configure Allowas-in :

CE18 : 

router bgp 20

neighbor 10.10.1.254  allowas-in

exit


CE20 : 

router bgp 20

neighbor 10.10.2.254 allowas-in

exit

end


Verification :

CE18 :

CE20 :









bisa dilihat gambar diatas command sh ip bgp Prefix CE20 (20.20.20.20) sekarang telah dipelajari oleh CE18 dan begitupun sebaliknya dari CE20 to CE18.


AS-Override


Masih topology yang sama, disini kita coba memakai AS-Override yang berfungsi untuk replace nomor AS CUS-B dengan

menjadi AS PE1, So may be it is not known by CUS-D.

Let’s remove priviously config on CE router :

CE18 :

router bgp 20

no neighbor 10.10.1.254 allowas-in

exit

CE20 : 

router bgp 20

no neighbor 10.10.2.254 allowas-in

exit

Verify BGP tidak memiliki koneksi antar loopbak antar CE B dan D :

CE18 :

CE20 :


Configure AS-Override on Router PE :

PE1 :

router bgp 1

address-family ipv4 vrf CUS-B

neighbor 10.10.1.2 as-override

exit

PE2 :

router bgp 1

address-family ipv4 vrf CUS-D

neighbor 10.10.2.2 as-override

exit


Verify BGP ASN telah berubah dari AS20 to AS1

BEFORE

CE18 & CE20:

AFTER

CE18 & CE20 :

Capture After config AS-Override Router CE18 telah mempelajari prefix dari CE20 (20.20.20.20) with AS1,

So Router PE telah replace AS20 to AS1 then disend to CE18, begitupun sebaliknya dari CE20 telah mempelajari

prefix dari CE18 (18.18.18.18) with AS1.






Thankss

Syawal adhitya


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