Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements
Users might experience few discrepancies in Search results. We are working on this on our side. We apologize for the inconvenience it may have caused.
New Member

mpls vpn dual home and backdoor links

I have the following network

CE1----OSPF------CE2

|                              |

|                              |

BGP(AS109)                    OSPF

|                              |

|                              |

PE1-------------------PE2         

|          ospf/ibgp      |

|          AS 9            |

P(RR)---------------------|

my goal from P is go to CE1-Lo0 via PE1

but it goes to PE1 - PE2 - CE2 - CE1

here the output of PE1

sho ip bgp vpnv4 all 172.9.0.11(CE1-LO)

BGP routing table entry for 9:9:172.9.0.11/32, version 124

Paths: (2 available, best #1, table ABC)

  Advertised to update-groups:

     3        

  Refresh Epoch 1

  Local

    9.9.0.5 (metric 11) from 9.9.0.7 (9.9.0.7)

      Origin incomplete, metric 21, localpref 100, valid, internal, best

      Extended Community: RT:9:9 OSPF DOMAIN ID:0x0005:0x0000006D0200

        OSPF RT:0.0.0.0:2:0 OSPF ROUTER ID:172.9.0.5:0

      Originator: 9.9.0.5, Cluster list: 9.9.0.7

      mpls labels in/out 57/33

  Refresh Epoch 1

  109

    172.9.113.11 from 172.9.113.11 (172.9.0.11)

      Origin incomplete, metric 0, localpref 100, valid, external

      Extended Community: RT:9:9

      mpls labels in/out 57/imp-null

HERE'S THE CONFIG OF PE1

address-family vpnv4

  neighbor 9.9.0.7 activate

  neighbor 9.9.0.7 send-community extended

exit-address-family

address-family ipv4 vrf ABC

  no synchronization

  network 172.9.0.3 mask 255.255.255.255

  redistribute connected

  neighbor 172.9.113.11 remote-as 109

  neighbor 172.9.113.11 activate

  neighbor 172.9.113.11 send-community both

  neighbor 172.9.113.11 as-override

  neighbor 172.9.113.11 send-label

exit-address-family

HERE'S THE CONFIG OF CE1:

router ospf 109

router-id 172.9.0.11

log-adjacency-changes

redistribute bgp 109 subnets tag 109

network 172.9.0.11 0.0.0.0 area 0

network 172.9.112.11 0.0.0.0 area 0

router bgp 109

bgp router-id 172.9.0.11

no bgp default ipv4-unicast

no bgp default route-target filter

neighbor 172.9.113.3 remote-as 9

!

address-family ipv4

  no synchronization

  redistribute ospf 109

  neighbor 172.9.113.3 activate

  neighbor 172.9.113.3 send-community both

  neighbor 172.9.113.3 send-label

  no auto-summary

exit-address-family

!

HERE'S THE CONFIG CE2

router ospf 109

router-id 172.9.0.12

log-adjacency-changes

network 172.9.0.12 0.0.0.0 area 0

network 172.9.112.12 0.0.0.0 area 0

network 172.9.125.12 0.0.0.0 area 0

LAST THE CONFIG PE2:

router ospf 109 vrf ABC

router-id 172.9.0.5

domain-tag 109

log-adjacency-changes

redistribute bgp 9 metric-type 1 subnets

network 172.9.0.5 0.0.0.0 area 0

network 172.9.125.5 0.0.0.0 area 0

router ospf 9

router-id 9.9.0.5

log-adjacency-changes

network 9.9.0.5 0.0.0.0 area 0

network 9.9.35.5 0.0.0.0 area 0

network 9.9.56.5 0.0.0.0 area 0

mpls traffic-eng router-id Loopback0

mpls traffic-eng area 0

mpls traffic-eng multicast-intact

router bgp 9

bgp router-id 9.9.0.5

no bgp default ipv4-unicast

no bgp default route-target filter

neighbor 9.9.0.7 remote-as 9

neighbor 9.9.0.7 update-source Loopback0

address-family vpnv4

  neighbor 9.9.0.7 activate

  neighbor 9.9.0.7 send-community extended

exit-address-family

!

address-family ipv4 vrf ABC

  no synchronization

  network 172.9.0.5 mask 255.255.255.255

  redistribute ospf 109 vrf ABC

exit-address-famil

Please let me know if need more info

Any help will be very much appreciated.

4 REPLIES
Cisco Employee

mpls vpn dual home and backdoor links

Hi Johnson,

I believe this is lab invironment and not production setup where you have to use BGP as PE-CE protocol on PE1 and OSPF as PE-CE protocol on PE2.

Now once you have two BGP route on PE1 VPN table, it will prefer route from PE2 over CE1 route because of lower AS-PATH attribute. To prefer CE1 route, you can set weight on PE1 router for neighbor 172.9.113.11 which will be locally significant.

BGP routing table entry for 9:9:172.9.0.11/32, version 124

Paths: (2 available, best #1, table ABC)

  Advertised to update-groups:

     3       

  Refresh Epoch 1

  Local

    9.9.0.5 (metric 11) from 9.9.0.7 (9.9.0.7)

      Origin incomplete, metric 21, localpref 100, valid, internal, best

      Extended Community: RT:9:9 OSPF DOMAIN ID:0x0005:0x0000006D0200

        OSPF RT:0.0.0.0:2:0 OSPF ROUTER ID:172.9.0.5:0

      Originator: 9.9.0.5, Cluster list: 9.9.0.7

      mpls labels in/out 57/33

  Refresh Epoch 1

  109                                                         >>>>>>>>>>>>>>>>>>>>>

    172.9.113.11 from 172.9.113.11 (172.9.0.11)

      Origin incomplete, metric 0, localpref 100, valid, external

      Extended Community: RT:9:9

      mpls labels in/out 57/imp-null

Regards,

Akash

New Member

mpls vpn dual home and backdoor links

Correct!

I did change the weight and it is the best path

But the traffic still goes to PE1 - PE2 - CE2 - CE1 instead of PE1-CE1

See the outputs below.

PE1:

sho ip bgp vpnv4 all 172.9.0.11

BGP routing table entry for 9:9:172.9.0.11/32, version 113

Paths: (2 available, best #2, table ABC)

  Advertised to update-groups:

     1        

  Local

    9.9.0.5 (metric 11) from 9.9.0.7 (9.9.0.7)

      Origin incomplete, metric 21, localpref 100, valid, internal

      Extended Community: RT:9:9 OSPF DOMAIN ID:0x0005:0x0000000A0200

        OSPF RT:0.0.0.0:2:0 OSPF ROUTER ID:172.9.0.5:512

      Originator: 9.9.0.5, Cluster list: 9.9.0.7

      mpls labels in/out 45/27

  109

    172.9.113.11 from 172.9.113.11 (172.9.0.11)

      Origin incomplete, metric 0, localpref 100, weight 100, valid, external, best

      Extended Community: RT:9:9

      mpls labels in/out 45/imp-null

TRACEROUTE:

P:

traceroute vrf ABC 172.9.0.11

  9.9.23.3 [MPLS: Labels 18/27 Exp 0] 16 msec <======PE1

  172.9.125.5 [MPLS: Label 27 Exp 0] 20 msec 20 msec 4 msec <======PE2

  172.9.125.12                                    16 msec 48 msec 24 msec <======CE2

  172.9.112.11                                     16 msec *  24 msec <======CE1

CE1----OSPF------CE2

|                              |

|                              |

BGP(AS109)         OSPF

|                              |

|                              |

PE1-------------------PE2         

|          ospf/ibgp      |

|          AS 9            |

P(RR)---------------------|

New Member

mpls vpn dual home and backdoor links

FROM RR ROUTER

P:

sho ip bgp vpnv4 all 172.9.0.11

BGP routing table entry for 9:9:172.9.0.11/32, version 147

Paths: (2 available, best #1, table ABC)

  Advertised to update-groups:

     1          2        

  Local, (Received from a RR-client)

    9.9.0.5 (metric 31) from 9.9.0.5 (9.9.0.5)

      Origin incomplete, metric 21, localpref 100, valid, internal, best

      Extended Community: RT:9:9 OSPF DOMAIN ID:0x0005:0x0000000A0200

        OSPF RT:0.0.0.0:2:0 OSPF ROUTER ID:172.9.0.5:512

      mpls labels in/out 51/27

  109, (Received from a RR-client)

    9.9.0.3 (metric 21) from 9.9.0.3 (9.9.0.3)

      Origin incomplete, metric 0, localpref 100, valid, internal

      Extended Community: RT:9:9

      mpls labels in/out 51/45

Cisco Employee

mpls vpn dual home and backdoor links

Hi,

you can determine it by yourself if you go through BGP best path selection algorithm and compare each BGP attribute between two BGP routes.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml

Regards,

Akash

465
Views
0
Helpful
4
Replies
CreatePlease to create content