MPLS OSPF Downward

NOTE

 

このような構成があった場合、R3はR15の経路をMP-BGP(iBGP AD200)とR13経由のOSPF (AD110)で学習することになる。ADだけで見ればOSPF経由がルーティングテーブルにのるが、このような回りまわっての学習はループ防止のためにおこなわれない。

 

 

ルーティングテーブルを見てもBフラグがついている

R3#sh ip route vrf VPN-A | b Gate
Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        10.3.13.0/24 is directly connected, FastEthernet1/0
L        10.3.13.3/32 is directly connected, FastEthernet1/0
O        10.4.13.0/24 [110/2] via 10.3.13.13, 00:20:47, FastEthernet1/0
B        10.5.15.0/24 [200/0] via 10.0.0.5, 01:41:04
O     192.168.13.0/24 [110/2] via 10.3.13.13, 01:46:15, FastEthernet1/0
B     192.168.15.0/24 [200/2] via 10.0.0.5, 01:39:16
R3#

 

LSDBもダウンビット（Downward）が付与され、使われないようになっている。これは capability vrf-lite がデフォルトでは無効化されているため。

R3#show ip ospf database summary

            OSPF Router with ID (10.0.0.3) (Process ID 65000)

            OSPF Router with ID (10.3.13.3) (Process ID 65100)

                Summary Net Link States (Area 10)

  LS age: 182
  Options: (No TOS-capability, DC, Downward)
  LS Type: Summary Links(Network)
  Link State ID: 10.5.15.0 (summary Network Number)
  Advertising Router: 10.3.13.3
  LS Seq Number: 80000004
  Checksum: 0xC1BB
  Length: 28
  Network Mask: /24
        MTID: 0         Metric: 1

  LS age: 1274
  Options: (No TOS-capability, DC, Downward)
  LS Type: Summary Links(Network)
  Link State ID: 10.5.15.0 (summary Network Number)
  Advertising Router: 10.4.14.4
  LS Seq Number: 80000003
  Checksum: 0xAECC
  Length: 28
  Network Mask: /24
        MTID: 0         Metric: 1

  LS age: 182
  Options: (No TOS-capability, DC, Downward)
  LS Type: Summary Links(Network)
  Link State ID: 192.168.15.0 (summary Network Number)
  Advertising Router: 10.3.13.3
  LS Seq Number: 80000004
  Checksum: 0xD849
  Length: 28
  Network Mask: /24
        MTID: 0         Metric: 2

  LS age: 1274
  Options: (No TOS-capability, DC, Downward)
  LS Type: Summary Links(Network)
  Link State ID: 192.168.15.0 (summary Network Number)
  Advertising Router: 10.4.14.4
  LS Seq Number: 80000003
  Checksum: 0xC55A
  Length: 28
  Network Mask: /24
        MTID: 0         Metric: 2

R3#

 

これを無効化せずにOSPF計算に使いたい場合に capability vrf-lite を入力する。デフォルトではshow run allでみると分かるが、no が付いた状態。

R3#show run all | sec router ospf 65100 vrf VPN-A
router ospf 65100 vrf VPN-A
 no capability vrf-lite

 

REFERENCE

MPLS VPN OSPF PE and CE Support

Chapter: MPLS VPN OSPF PE and CE Support

OSPF Commands
capability vrf-lite

 

 

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