L3VPN MP-BGP with multi-vrf implicit-null label in PE router for CE networks #17539

nitinraj92 · 2024-11-30T19:49:03Z

nitinraj92
Nov 30, 2024

Hi All,
I am trying to bring up a L3VPN with MP-BGP. The mpls ldp is advertising implicit-null for CE routes and due to this, that network is unreachable. Please let me know if I am missing some configuration.
My setup is:

Below is the configurations on PE routers:

router bgp 64501
 bgp router-id 4.4.4.4
 no bgp ebgp-requires-policy
 neighbor 172.16.4.2 remote-as 64501
 neighbor 172.16.5.2 remote-as 64501
 !
 address-family ipv4 vpn
  neighbor 172.16.4.2 activate
  neighbor 172.16.5.2 activate
 exit-address-family
exit
!
router bgp 64501 vrf vrf-green
 bgp router-id 192.168.10.10
 no bgp ebgp-requires-policy
 neighbor 192.168.10.10 remote-as 64401
 !
 address-family ipv4 unicast
  network 192.168.10.0/24
  redistribute connected
  neighbor 192.168.10.10 next-hop-self
  neighbor 192.168.10.10 default-originate
  rd vpn export 100:100
  rt vpn both 100:100
  export vpn
  import vpn
 exit-address-family
exit
!
router bgp 64501 vrf vrf-black
 bgp router-id 192.168.11.10
 no bgp ebgp-requires-policy
 neighbor 192.168.11.10 remote-as 64411
 !
 address-family ipv4 unicast
  network 192.168.11.0/24
  redistribute connected
  neighbor 192.168.11.10 default-originate
  rd vpn export 100:200
  rt vpn both 100:200
  export vpn
  import vpn
 exit-address-family
exit
!
router ospf
 ospf router-id 4.4.4.4
 network 0.0.0.0/0 area 0
 mpls ldp-sync
exit
!
mpls ldp
 router-id 4.4.4.4
 ordered-control
 install allow-broken-lsp
 neighbor 1.1.1.1 password test
 !
 address-family ipv4
  discovery transport-address 4.4.4.4
  label local advertise explicit-null
  !
  interface wan0
  exit
  !
 exit-address-family
 !
exit

Configuration of P routers:

router ospf
 ospf router-id 1.1.1.1
 network 0.0.0.0/0 area 0
exit
!
mpls ldp
 router-id 1.1.1.1
 ordered-control
 neighbor 2.2.2.2 password test
 neighbor 4.4.4.4 password test
 neighbor 5.5.5.5 password test
 !
 address-family ipv4
  discovery transport-address 1.1.1.1
  label local advertise explicit-null
  !
  interface ens18
  exit
  !
  interface ens19
  exit
  !
  interface ens20
  exit
  !
 exit-address-family
 !
exit

The route status in PE1 router shows PE2 route as implicit-null and because of this the packet is getting dropped in P router.

rtr-986aa000# show ip route vrf vrf-green
VRF vrf-green:
K * 0.0.0.0/0 [255/8192] unreachable (ICMP unreachable), 00:43:13
K>* 0.0.0.0/0 [0/0] is directly connected, lan0.100, 00:43:13
B>* 10.10.10.0/24 [20/0] via 192.168.10.10, lan0.100, weight 1, 00:43:10
B>  20.20.20.0/24 [200/0] via 172.16.4.2 (vrf default) (recursive), label implicit-null, weight 1, 00:02:28
  *                         via 172.16.3.1, wan0 (vrf default), label IPv4 Explicit Null/implicit-null, weight 1, 00:02:28
B>  30.30.30.0/24 [200/0] via 172.16.5.2 (vrf default) (recursive), label implicit-null, weight 1, 00:02:28
  *                         via 172.16.3.1, wan0 (vrf default), label 23/implicit-null, weight 1, 00:02:28
C>* 192.168.10.0/24 is directly connected, lan0.100, 00:43:13
L>* 192.168.10.1/32 is directly connected, lan0.100, 00:43:13
B>  192.168.20.0/24 [200/0] via 172.16.4.2 (vrf default) (recursive), label implicit-null, weight 1, 00:02:28
  *                           via 172.16.3.1, wan0 (vrf default), label IPv4 Explicit Null/implicit-null, weight 1, 00:02:28
B>  192.168.30.0/24 [200/0] via 172.16.5.2 (vrf default) (recursive), label implicit-null, weight 1, 00:02:28
  *                           via 172.16.3.1, wan0 (vrf default), label 23/implicit-null, weight 1, 00:02:28

mpls label status:

rtr-986aa000# show mpls ldp neighbor
AF   ID              State       Remote Address    Uptime
ipv4 1.1.1.1         OPERATIONAL 1.1.1.1         00:00:13
rtr-986aa000# show mpls ldp binding
AF   Destination          Nexthop         Local Label Remote Label  In Use
ipv4 1.1.1.1/32           1.1.1.1         16          exp-null         yes
ipv4 2.2.2.2/32           1.1.1.1         17          19               yes
ipv4 3.3.3.3/32           1.1.1.1         18          20               yes
ipv4 4.4.4.4/32           0.0.0.0         exp-null    -                 no
ipv4 5.5.5.5/32           1.1.1.1         19          18               yes
ipv4 6.6.6.6/32           1.1.1.1         20          21               yes
ipv4 10.5.0.0/24          1.1.1.1         21          25               yes
ipv4 10.5.0.69/32         1.1.1.1         -           16                no
ipv4 172.16.1.0/30        1.1.1.1         22          exp-null         yes
ipv4 172.16.2.0/30        1.1.1.1         23          22               yes
ipv4 172.16.3.0/30        1.1.1.1         exp-null    exp-null          no
ipv4 172.16.4.0/30        1.1.1.1         24          exp-null         yes
ipv4 172.16.5.0/30        1.1.1.1         25          23               yes
ipv4 172.16.6.0/30        1.1.1.1         26          24               yes

rtr-986aa000# show mpls table
 Inbound Label  Type  Nexthop     Outbound Label
 -----------------------------------------------------
 16             LDP   172.16.3.1  IPv4 Explicit Null
 17             LDP   172.16.3.1  19
 18             LDP   172.16.3.1  20
 19             LDP   172.16.3.1  18
 20             LDP   172.16.3.1  21
 21             LDP   172.16.3.1  25
 22             LDP   172.16.3.1  IPv4 Explicit Null
 23             LDP   172.16.3.1  22
 24             LDP   172.16.3.1  IPv4 Explicit Null
 25             LDP   172.16.3.1  23
 26             LDP   172.16.3.1  24

The routes and mpls status in P router connecting PE1 and PE2:

ISP-P1# show ip route
Codes: K - kernel route, C - connected, L - local, S - static,
       R - RIP, O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
       f - OpenFabric, t - Table-Direct,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

O   1.1.1.1/32 [110/10] via 0.0.0.0, lo0 onlink, weight 1, 01:59:30
L * 1.1.1.1/32 is directly connected, lo0, 04:17:16
C>* 1.1.1.1/32 is directly connected, lo0, 04:17:16
O>* 2.2.2.2/32 [110/110] via 172.16.1.1, ens20, label IPv4 Explicit Null, weight 1, 01:59:07
O>* 3.3.3.3/32 [110/210] via 172.16.1.1, ens20, label 21, weight 1, 01:58:57
O>* 4.4.4.4/32 [110/110] via 172.16.3.2, ens18, label IPv4 Explicit Null, weight 1, 00:02:13
O>* 5.5.5.5/32 [110/110] via 172.16.4.2, ens19, label IPv4 Explicit Null, weight 1, 01:10:15
O>* 6.6.6.6/32 [110/310] via 172.16.1.1, ens20, label 23, weight 1, 01:09:13
O>* 10.5.0.0/24 [110/200] via 172.16.1.1, ens20, label IPv4 Explicit Null, weight 1, 01:59:07
K>* 10.5.0.69/32 [0/0] via 172.16.1.1, ens20, 04:17:16
O>* 169.254.100.0/24 [110/110] via 172.16.4.2, ens19, weight 1, 01:10:15
O   172.16.1.0/30 [110/100] is directly connected, ens20, weight 1, 01:59:30
C>* 172.16.1.0/30 is directly connected, ens20, 04:17:16
L>* 172.16.1.2/32 is directly connected, ens20, 04:17:16
O>* 172.16.2.0/30 [110/200] via 172.16.1.1, ens20, label IPv4 Explicit Null, weight 1, 01:59:07
O   172.16.3.0/30 [110/100] is directly connected, ens18, weight 1, 01:50:40
C>* 172.16.3.0/30 is directly connected, ens18, 04:17:16
L>* 172.16.3.1/32 is directly connected, ens18, 04:17:16
O   172.16.4.0/30 [110/100] is directly connected, ens19, weight 1, 01:16:25
C>* 172.16.4.0/30 is directly connected, ens19, 04:17:16
L>* 172.16.4.1/32 is directly connected, ens19, 04:17:16
O>* 172.16.5.0/30 [110/300] via 172.16.1.1, ens20, label 22, weight 1, 01:11:52
O>* 172.16.6.0/30 [110/300] via 172.16.1.1, ens20, label 24, weight 1, 01:58:57

ISP-P1# show mpls ldp neighbor
AF   ID              State       Remote Address    Uptime
ipv4 2.2.2.2         OPERATIONAL 2.2.2.2         04:15:19
ipv4 4.4.4.4         OPERATIONAL 4.4.4.4         00:01:16
ipv4 5.5.5.5         OPERATIONAL 5.5.5.5         00:00:01
ISP-P1# show mpls ldp binding
AF   Destination          Nexthop         Local Label Remote Label  In Use
ipv4 1.1.1.1/32           4.4.4.4         exp-null    16                no
ipv4 2.2.2.2/32           2.2.2.2         19          exp-null         yes
ipv4 2.2.2.2/32           4.4.4.4         19          17                no
ipv4 3.3.3.3/32           2.2.2.2         20          21               yes
ipv4 3.3.3.3/32           4.4.4.4         20          18                no
ipv4 4.4.4.4/32           4.4.4.4         17          exp-null         yes
ipv4 5.5.5.5/32           4.4.4.4         18          19                no
ipv4 5.5.5.5/32           5.5.5.5         18          exp-null         yes
ipv4 6.6.6.6/32           2.2.2.2         21          23               yes
ipv4 6.6.6.6/32           4.4.4.4         21          20                no
ipv4 10.5.0.0/24          2.2.2.2         25          exp-null         yes
ipv4 10.5.0.0/24          4.4.4.4         25          21                no
ipv4 10.5.0.69/32         0.0.0.0         16          -                 no
ipv4 172.16.1.0/30        2.2.2.2         exp-null    exp-null          no
ipv4 172.16.1.0/30        4.4.4.4         exp-null    22                no
ipv4 172.16.2.0/30        2.2.2.2         22          exp-null         yes
ipv4 172.16.2.0/30        4.4.4.4         22          23                no
ipv4 172.16.3.0/30        4.4.4.4         exp-null    exp-null          no
ipv4 172.16.4.0/30        4.4.4.4         exp-null    24                no
ipv4 172.16.4.0/30        5.5.5.5         exp-null    exp-null          no
ipv4 172.16.5.0/30        2.2.2.2         23          22               yes
ipv4 172.16.5.0/30        4.4.4.4         23          25                no
ipv4 172.16.6.0/30        2.2.2.2         24          24               yes
ipv4 172.16.6.0/30        4.4.4.4         24          26                no

ISP-P1# show mpls table
 Inbound Label  Type  Nexthop     Outbound Label
 -----------------------------------------------------
 17             LDP   172.16.3.2  IPv4 Explicit Null
 18             LDP   172.16.4.2  IPv4 Explicit Null
 19             LDP   172.16.1.1  IPv4 Explicit Null
 20             LDP   172.16.1.1  21
 21             LDP   172.16.1.1  23
 22             LDP   172.16.1.1  IPv4 Explicit Null
 23             LDP   172.16.1.1  22
 24             LDP   172.16.1.1  24
 25             LDP   172.16.1.1  IPv4 Explicit Null

Please let me know if there is some issue in my configuration. The same setup was working without vrfs.
Let me know if you need more information regarding the setup. Thanks in advance.

Answered by nitinraj92

Dec 2, 2024

Got the solution:
Need to use loopback interface for bgp. With this configuration in PE devices, able to perform the label switching correctly.

 vrf vrf-green
 vni 10
exit-vrf
!
vrf vrf-black
 vni 11
exit-vrf
!
interface lo0
 ip address 4.4.4.4/32
exit
!
router bgp 64501
 bgp router-id 4.4.4.4
 no bgp ebgp-requires-policy
 neighbor 5.5.5.5 remote-as 64501
 neighbor 5.5.5.5 update-source lo0
 neighbor 6.6.6.6 remote-as 64501
 neighbor 6.6.6.6 update-source lo0
 !
 address-family ipv4 vpn
  neighbor 5.5.5.5 activate
  neighbor 6.6.6.6 activate
 exit-address-family
exit
!
router bgp 64501 vrf vrf-green
 bgp router-id 192.168.10.10
 no bgp ebgp-requires-policy
 neighbor 192.168.10.10 remote-a…

View full answer

nitinraj92 · 2024-12-02T11:26:52Z

nitinraj92
Dec 2, 2024
Author

Got the solution:
Need to use loopback interface for bgp. With this configuration in PE devices, able to perform the label switching correctly.

 vrf vrf-green
 vni 10
exit-vrf
!
vrf vrf-black
 vni 11
exit-vrf
!
interface lo0
 ip address 4.4.4.4/32
exit
!
router bgp 64501
 bgp router-id 4.4.4.4
 no bgp ebgp-requires-policy
 neighbor 5.5.5.5 remote-as 64501
 neighbor 5.5.5.5 update-source lo0
 neighbor 6.6.6.6 remote-as 64501
 neighbor 6.6.6.6 update-source lo0
 !
 address-family ipv4 vpn
  neighbor 5.5.5.5 activate
  neighbor 6.6.6.6 activate
 exit-address-family
exit
!
router bgp 64501 vrf vrf-green
 bgp router-id 192.168.10.10
 no bgp ebgp-requires-policy
 neighbor 192.168.10.10 remote-as 64401
 neighbor 192.168.10.10 update-source lan0.100
 !
 address-family ipv4 unicast
  network 192.168.10.0/24
  redistribute connected
  label vpn export auto
  rd vpn export 100:100
  rt vpn both 100:100
  export vpn
  import vpn
 exit-address-family
exit
!
router bgp 64501 vrf vrf-black
 bgp router-id 192.168.11.10
 no bgp ebgp-requires-policy
 neighbor 192.168.11.10 remote-as 64411
 neighbor 192.168.11.10 update-source lan0.200
 !
 address-family ipv4 unicast
  network 192.168.11.0/24
  redistribute connected
  label vpn export auto
  rd vpn export 100:200
  rt vpn both 100:200
  export vpn
  import vpn
 exit-address-family
exit
!
router ospf
 ospf router-id 4.4.4.4
 network 0.0.0.0/0 area 0
exit
!
mpls ldp
 router-id 4.4.4.4
 neighbor 1.1.1.1 password test
 !
 address-family ipv4
  discovery transport-address 4.4.4.4
  label local allocate host-routes
  !
  interface wan0
  exit
  !
 exit-address-family
 !
exit

with this the labels are getting pushed correctly.

rtr-986aa000# show ip route vrf vrf-green
Codes: K - kernel route, C - connected, L - local, S - static,
       R - RIP, O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
       f - OpenFabric, t - Table-Direct,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

VRF vrf-green:
K>* 0.0.0.0/0 [255/8192] unreachable (ICMP unreachable), 04:33:05
B>* 10.10.10.0/24 [20/0] via 192.168.10.10, lan0.100, weight 1, 04:33:02
B>  20.20.20.0/24 [200/0] via 5.5.5.5 (vrf default) (recursive), label 80, weight 1, 02:29:50
  *                         via 172.16.3.1, wan0 (vrf default), label 17/80, weight 1, 02:29:50
B>  30.30.30.0/24 [200/0] via 6.6.6.6 (vrf default) (recursive), label 80, weight 1, 02:29:50
  *                         via 172.16.3.1, wan0 (vrf default), label 21/80, weight 1, 02:29:50
C>* 192.168.10.0/24 is directly connected, lan0.100, 04:33:05
L>* 192.168.10.1/32 is directly connected, lan0.100, 04:33:05
B>  192.168.20.0/24 [200/0] via 5.5.5.5 (vrf default) (recursive), label 80, weight 1, 02:29:50
  *                           via 172.16.3.1, wan0 (vrf default), label 17/80, weight 1, 02:29:50
B>  192.168.30.0/24 [200/0] via 6.6.6.6 (vrf default) (recursive), label 80, weight 1, 02:29:50
  *                           via 172.16.3.1, wan0 (vrf default), label 21/80, weight 1, 02:29:50
rtr-986aa000# show mpls table
 Inbound Label  Type    Nexthop        Outbound Label
 ----------------------------------------------------------
 16             LDP     172.16.3.1     implicit-null
 17             LDP     172.16.3.1     18
 18             LDP     172.16.3.1     17
 19             LDP     172.16.3.1     19
 20             LDP     172.16.3.1     21
 80             BGP     vrf-green      -
 81             BGP     vrf-black      -

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L3VPN MP-BGP with multi-vrf implicit-null label in PE router for CE networks #17539

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L3VPN MP-BGP with multi-vrf implicit-null label in PE router for CE networks #17539

nitinraj92 Nov 30, 2024

Replies: 1 comment

nitinraj92 Dec 2, 2024 Author

nitinraj92
Nov 30, 2024

nitinraj92
Dec 2, 2024
Author