OSPF トータリースタブ

GNS3上でOSPFのトータリースタブを構成するまでの手順を再確認してみます。
OSPF_06_01

[RouterA]

interface Loopback0
 ip address 1.1.1.1 255.255.255.255
!
interface Ethernet0/0
 ip address 10.0.1.2 255.255.255.0
 half-duplex
!
router ospf 1
 log-adjacency-changes
 network 10.0.1.0 0.0.0.255 area 1
!

[RouterB]

interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!
interface Ethernet0/0
 ip address 10.0.1.1 255.255.255.0
 half-duplex
!
interface Ethernet0/1
 ip address 10.0.0.1 255.255.255.0
 half-duplex
!
router ospf 1
 log-adjacency-changes
 network 10.0.0.0 0.0.0.255 area 0
 network 10.0.1.0 0.0.0.255 area 1
!

[RouterC]

interface Loopback0
 ip address 3.3.3.3 255.255.255.255
!
interface Ethernet0/0
 ip address 10.0.0.2 255.255.255.0
 half-duplex
!
interface Ethernet0/1
 ip address 192.168.1.1 255.255.255.0
 half-duplex
!
router ospf 1
 log-adjacency-changes
 redistribute rip subnets :RIPの経路をOSPFで再配布
 network 10.0.0.0 0.0.0.255 area 0
 default-metric 30 :OSPFへ再配布するときのコスト
!
router rip
 network 192.168.1.0
!

[RouterD]

interface Loopback0
 ip address 4.4.4.4 255.255.255.255
!
interface Ethernet0/0
 ip address 192.168.1.2 255.255.255.0
 half-duplex
!
interface Ethernet0/1
 ip address 192.168.110.1 255.255.255.0
 half-duplex
!
interface Ethernet0/2
 ip address 192.168.120.1 255.255.255.0
 half-duplex
!
router rip
 network 192.168.1.0
 network 192.168.110.0
 network 192.168.120.0
!
ip route 0.0.0.0 0.0.0.0 192.168.1.1
!

RouterAのOSPFデータベースを確認します。

RouterA#sh ip ospf database
 OSPF Router with ID (1.1.1.1) (Process ID 1)

 Router Link States (Area 1) :Type1
Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 1871 0x80000002 0x0031D6 1
2.2.2.2 2.2.2.2 1872 0x80000002 0x00D926 1

 Net Link States (Area 1) :Type2
Link ID ADV Router Age Seq# Checksum
10.0.1.1 2.2.2.2 1872 0x80000001 0x0042D7

 Summary Net Link States (Area 1) :type3
Link ID ADV Router Age Seq# Checksum
10.0.0.0 2.2.2.2 1913 0x80000001 0x002FF1

 Summary ASB Link States (Area 1) :Type4
Link ID ADV Router Age Seq# Checksum
3.3.3.3 2.2.2.2 1872 0x80000001 0x001905

 Type-5 AS External Link States :Type5
Link ID ADV Router Age Seq# Checksum Tag
192.168.1.0 3.3.3.3 1918 0x80000001 0x0035EA 0
192.168.110.0 3.3.3.3 1917 0x80000001 0x008131 0
192.168.120.0 3.3.3.3 1917 0x80000001 0x001395 0

LSA2~LSA5はこんな感じで配送されてきます。LSA1は各ルータが生成し配布します。
OSPF_06_02

ここからArea1をスタブにします。設定はRoterAとRouterBの両方に施す必要があるので注意。

RouterA(config-router)#area 1 stub
RouterB(config-router)#area 1 stub

RouterAのOSPFデータベースを見てみると、先ほどと違いType4、Type5が無くなり代わりにType3でデフォルトルートが通知されてくるのがわかります。

RouterA#sh ip ospf database
OSPF Router with ID (1.1.1.1) (Process ID 1)

Router Link States (Area 1)
Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 54 0x80000006 0x0047BE 1
2.2.2.2 2.2.2.2 55 0x80000006 0x00EF0E 1

Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
10.0.1.1 2.2.2.2 50 0x80000005 0x0058BF

Summary Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
0.0.0.0 2.2.2.2 56 0x80000001 0x0075C0
10.0.0.0 2.2.2.2 56 0x80000004 0x0047D8

ルーティングテーブルも確認。

RouterA#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
 D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
 N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
 E1 - OSPF external type 1, E2 - OSPF external type 2
 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
 ia - IS-IS inter area, * - candidate default, U - per-user static route
 o - ODR, P - periodic downloaded static route

Gateway of last resort is 10.0.1.1 to network 0.0.0.0

 1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
 10.0.0.0/24 is subnetted, 2 subnets
O IA 10.0.0.0 [110/20] via 10.0.1.1, 00:05:13, Ethernet0/0
C 10.0.1.0 is directly connected, Ethernet0/0
O*IA 0.0.0.0/0 [110/11] via 10.0.1.1, 00:05:13, Ethernet0/0

さらに外部エリア(ここではArea0)の経路情報もデフォルトルートで代替させる「トータリースタブ」を設定してみます。

RouterA(config-router)#area 1 stub no-summary
RouterB(config-router)#area 1 stub no-summary

OSPFデータベースを確認。

RouterA#sh ip ospf database

            OSPF Router with ID (1.1.1.1) (Process ID 1)
                Router Link States (Area 1)
Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.1         1.1.1.1         654         0x80000006 0x0047BE 1
2.2.2.2         2.2.2.2         655         0x80000006 0x00EF0E 1

                Net Link States (Area 1)
Link ID         ADV Router      Age         Seq#       Checksum
10.0.1.1        2.2.2.2         650         0x80000005 0x0058BF

                Summary Net Link States (Area 1)
Link ID         ADV Router      Age         Seq#       Checksum
0.0.0.0         2.2.2.2         60          0x80000002 0x0073C1


ルーティングテーブルも確認します。

RouterA#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is 10.0.1.1 to network 0.0.0.0

     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback0
     10.0.0.0/24 is subnetted, 1 subnets
C       10.0.1.0 is directly connected, Ethernet0/0
O*IA 0.0.0.0/0 [110/11] via 10.0.1.1, 00:01:29, Ethernet0/0
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