OSPF_SL0 from FULL to DOWN, Neighbor Down: Interface down or

Hi All,

I am labbing up a sham-link to prefer MPLS path over backdoor OSPF route.
The lab set-up is simple as below:

R5 -> R4 (RR) -> R6

I am creating a sham-link from R5 to R6, so I followed the below steps:

1. Create loopback 200 on both routers and assign to vrf

    R5

    interface Loopback200
     ip vrf forwarding VPN_A
    ip address 1.1.1.1 255.255.255.255

    R6

    interface Loopback200
    ip vrf forwarding VPN_A
    ip address 2.2.2.2 255.255.255.255

2. Advertise /32 loopback other than OSPF, so advertised via BGP

    R5

    router bgp 100
    address-family ipv4 vrf VPN_A
    network 1.1.1.1 mask 255.255.255.255

    R6

    router bgp 100
    address-family ipv4 vrf VPN_A
    network 2.2.2.2 mask 255.255.255.255

3. create sham-link

    R5

    router ospf 10 vrf VPN_A
    area 1 sham-link 1.1.1.1 2.2.2.2 cost 1

    R6

    router ospf 10 vrf VPN_A
    area 1 sham-link 2.2.2.2 1.1.1.1 cost 1

Once I enabled sham-link command, the link starts to flaps. The OSPF_SL
interface comes up and than within seconds it shows Interface down or
detached. Please see full configuration as below with error messages

R5

interface Loopback200
 ip vrf forwarding VPN_A
 ip address 1.1.1.1 255.255.255.255

router ospf 10 vrf VPN_A
 log-adjacency-changes
 redistribute bgp 100 subnets tag 667
 network 155.1.58.5 0.0.0.0 area 1
 area 1 sham-link 1.1.1.1 2.2.2.2 cost 1

router ospf 1
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0

router bgp 100
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 150.1.4.4 remote-as 100
 neighbor 150.1.4.4 update-source Loopback0
 !
 address-family vpnv4
  neighbor 150.1.4.4 activate
  neighbor 150.1.4.4 send-community extended
 exit-address-family

 address-family ipv4 vrf VPN_A
  redistribute connected
  redistribute static
  redistribute ospf 10 vrf VPN_A
  no synchronization
  network 1.1.1.1 mask 255.255.255.255
 exit-address-family

R6

interface Loopback200
 ip vrf forwarding VPN_A
 ip address 2.2.2.2 255.255.255.255

router ospf 10 vrf VPN_A
 log-adjacency-changes
 summary-address 172.16.0.0 255.255.0.0
 redistribute bgp 100 subnets tag 666
 network 155.1.67.6 0.0.0.0 area 1
area 1 sham-link 2.2.2.2 1.1.1.1 cost 1

router ospf 1
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0

router bgp 100
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 150.1.4.4 remote-as 100
 neighbor 150.1.4.4 update-source Loopback0
 !
 address-family vpnv4
  neighbor 150.1.4.4 activate
  neighbor 150.1.4.4 send-community extended
 exit-address-family

 address-family ipv4 vrf VPN_A
  redistribute connected
  redistribute static
  redistribute ospf 10 vrf VPN_A
  no synchronization
  network 2.2.2.2 mask 255.255.255.255
 exit-address-family

Mar 1 00:56:20.951: %OSPF-5-ADJCHG: Process 10, Nbr 172.16.5.5 on OSPF_SL0
from LOADING to FULL, Loading Done
*Mar 1 00:56:22.103: %OSPF-5-ADJCHG: Process 10, Nbr 172.16.5.5 on OSPF_SL0
from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar 1 00:56:40.835: %OSPF-5-ADJCHG: Process 10, Nbr 172.16.5.5 on OSPF_SL0
from LOADING to FULL, Loading Done
*Mar 1 00:56:42.099: %OSPF-5-ADJCHG: Process 10, Nbr 172.16.5.5 on OSPF_SL0
from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar 1 00:57:01.427: %OSPF-5-ADJCHG: Process 10, Nbr 172.16.5.5 on OSPF_SL0
from LOADING to FULL, Loading Done
*Mar 1 00:57:02.103: %OSPF-5-ADJCHG: Process 10, Nbr 172.16.5.5 on OSPF_SL0
from FULL to DOWN, Neighbor Down: Interface down or detached

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Received on Fri Jul 01 2011 - 21:53:53 ART