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Unable to Ping Across a Redundant Link When primary Link Through Area Zero is Pulled forcing Traffic Across Area Other than Zero

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TitleUnable to Ping Across a Redundant Link When primary Link Through Area Zero is Pulled forcing Traffic Across Area Other than Zero
Symptoms
  •  
    •  
      • Disconnect link between area zero, forcing traffic through area other than zero,  stops ping to devices across the link  that are not in area zero
  • ABR  cannot ping back to interfaces
  • show ip route on ABR does not show route of device that cannot ping
  • show ip ospf database shows the subnet (10.140.8.0) as a type three, learned in area four, even though the link is on a backbone router in area zero because withthe the link to area zero disconnected the route is learned across  area four
7100-Seriessu-router-config)->show ip ospf database

OSPF Process Id 1

Displaying LS Type 1 Advertisements (Area 0.0.0.0)

LinkID ADV Router Age Seq# Checksum

9.9.9.7 9.9.9.7 1786 80000002 0x3d8a
9.9.9.8 9.9.9.8 790 80000005 0xac83
9.9.9.9 9.9.9.9 327 80000065 0x25ee
10.140.9.6 10.140.9.6 790 80000005 0x17a2

Displaying LS Type 2 Advertisements (Area 0.0.0.0)

LinkID ADV Router Age Seq# Checksum

10.140.6.1 9.9.9.9 1792 80000001 0xdd77
10.140.8.1 9.9.9.8 794 80000002 0xd6f9

Displaying LS Type 3 Advertisements (Area 0.0.0.0)

LinkID ADV Router Age Seq# Checksum

10.140.9.4 9.9.9.7 353 80000002 0x147b
10.140.9.4 10.140.9.6 796 80000002 0xf417

Displaying LS Type 1 Advertisements (Area 0.0.0.4)

LinkID ADV Router Age Seq# Checksum

9.9.9.7 9.9.9.7 1794 80000005 0xd5e0
10.140.9.6 10.140.9.6 596 80000006 0x9518

Displaying LS Type 2 Advertisements (Area 0.0.0.4)

LinkID ADV Router Age Seq# Checksum

10.140.9.6 10.140.9.6 596 80000002 0x72d6

Displaying LS Type 3 Advertisements (Area 0.0.0.4)

LinkID ADV Router Age Seq# Checksum

9.9.9.8 10.140.9.6 779 80000002 0x7a05
9.9.9.9 9.9.9.7 1782 80000001 0x9171
10.0.0.0 9.9.9.7 1782 80000001 0xae6e
10.140.6.0 9.9.9.7 1795 80000001 0x5f38
10.140.8.0 10.140.9.6 790 80000002 0x28e8
  • Traceroute from ABR causes error
7100-Seriessu-router-config)->traceroute 10.140.8.1
traceroute: Could not determine source address.
  • Reconnect link between area zero router and ping returns
Environment
  • S-Series
    • 7100-Series
      • Securestack
  • K-Series
    • Cisco
Cause
Breaking the link between area zero routers causes the network to have two discontiguous area zeroes
Resolution

Move all of the links between core routers to area zero, so that the primary and backup links are in area zero and a broken link does not cause a linnk across an ABR to become the only data path.
Additional notes

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