OSPF Multi Area – ルート集約のnot-advertiseオプション 017

今回はOSPFのLSA Type 3のルート集約を行う際に使用するrangeコマンドのnot-advertiseオプションの動作を解説します。

 

座学

rangeコマンドのnot-advertiseオプション

rangeコマンドのnot-advertiseオプションを使用することで、以前の記事で解説したOut方向のFilter Listと同様に、他のAreaに投入するルート情報をフィルタリング可能です。

area <area-id> range <network-address> <subnet-mask> not-advertiseコマンドを設定した場合、<area-id>で指定したAreaから他のAreaに対して、<network-address> <subnet-mask>で指定したプレフィックスを格納したLSA Type 3が投入されなくなります。

 

実機での動作確認

検証内容

R1のg2でOSPF Area 0を有効にします。
R2のg2でOSPF Area 0、g3とg4でOSPF Area 2を有効にします。
R1、R2のNetwork TypeにはPoint-to-Pointを使用します。

 

初期設定


interface GigabitEthernet2
 ip address 10.1.1.1 255.255.255.0
 ip ospf network point-to-point
!
router ospf 1
 router-id 1.1.1.1
 network 10.1.1.0 0.0.0.255 area 0
            


interface GigabitEthernet2
 ip address 10.1.1.2 255.255.255.0
 ip ospf network point-to-point
!
interface GigabitEthernet3
 ip address 20.1.1.2 255.255.255.0
!
interface GigabitEthernet4
 ip address 20.2.2.2 255.255.255.0
!
router ospf 1
 router-id 2.2.2.2
 network 10.1.1.0 0.0.0.255 area 0
 network 20.1.1.0 0.0.0.255 area 2
 network 20.2.2.0 0.0.0.255 area 2

 

not-advertiseオプション有りのrangeコマンド設定前

OSPFプロセスの状態確認

R2のOSPFでnot-advertiseオプション有りのrangeコマンドが設定されていないことが確認できます。

R2

R2#show ip ospf
 Routing Process "ospf 1" with ID 2.2.2.2
 Start time: 1d07h, Time elapsed: 00:00:37.969
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 Supports Link-local Signaling (LLS)
 Supports area transit capability
 Supports NSSA (compatible with RFC 3101)
 Supports Database Exchange Summary List Optimization (RFC 5243)
 Event-log enabled, Maximum number of events: 1000, Mode: cyclic
 It is an area border router
 Router is not originating router-LSAs with maximum metric
 Initial SPF schedule delay 50 msecs
 Minimum hold time between two consecutive SPFs 200 msecs
 Maximum wait time between two consecutive SPFs 5000 msecs
 Incremental-SPF disabled
 Initial LSA throttle delay 50 msecs
 Minimum hold time for LSA throttle 200 msecs
 Maximum wait time for LSA throttle 5000 msecs
 Minimum LSA arrival 100 msecs
 LSA group pacing timer 240 secs
 Interface flood pacing timer 33 msecs
 Retransmission pacing timer 66 msecs
 EXCHANGE/LOADING adjacency limit: initial 300, process maximum 300
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 2. 2 normal 0 stub 0 nssa
 Number of areas transit capable is 0
 External flood list length 0
 IETF NSF helper support enabled
 Cisco NSF helper support enabled
 Reference bandwidth unit is 100 mbps
    Area BACKBONE(0)
        Number of interfaces in this area is 1
        Area has no authentication
        SPF algorithm last executed 00:00:37.898 ago
        SPF algorithm executed 1 times
        Area ranges are
        Number of LSA 4. Checksum Sum 0x019C77
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0
    Area 2
        Number of interfaces in this area is 2
        Area has no authentication
        SPF algorithm last executed 00:00:14.945 ago
        SPF algorithm executed 3 times
        Area ranges are
        Number of LSA 2. Checksum Sum 0x010205
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0

 

LSDBの状態確認

R2がArea 0に対して20.1.1.0/24と20.2.2.0/24を格納したLSA Type 3を投入していることが確認できます。

R2

R2#show ip ospf database

            OSPF Router with ID (2.2.2.2) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.1         1.1.1.1         46          0x80000013 0x00BB2C 2
2.2.2.2         2.2.2.2         45          0x80000002 0x008072 2

                Summary Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
20.1.1.0        2.2.2.2         45          0x80000001 0x003BE2
20.2.2.0        2.2.2.2         22          0x80000001 0x0024F7

                Router Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum Link count
2.2.2.2         2.2.2.2         22          0x80000003 0x00449B 2

                Summary Net Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum
10.1.1.0        2.2.2.2         45          0x80000001 0x00BD6A

 

SPFの計算結果の確認

R1はOSPF経由で20.1.1.0/24と20.2.2.0/24を学習していることが確認できます。

R1

R1#show ip ospf rib

            OSPF Router with ID (1.1.1.1) (Process ID 1)

                Base Topology (MTID 0)

OSPF local RIB
Codes: * - Best, > - Installed in global RIB

*   10.1.1.0/24, Intra, cost 1, area 0, Connected
      via 10.1.1.1, GigabitEthernet2
*>  20.1.1.0/24, Inter, cost 2, area 0
      via 10.1.1.2, GigabitEthernet2
*>  20.2.2.0/24, Inter, cost 2, area 0
      via 10.1.1.2, GigabitEthernet2

 

SPFの計算結果の確認

R1のルーティングテーブルに20.1.1.0/24と20.2.2.0/24が投入されていることが確認できます。

R1

R1#show ip route ospf
      20.0.0.0/24 is subnetted, 2 subnets
O IA     20.1.1.0 [110/2] via 10.1.1.2, 00:01:27, GigabitEthernet2
O IA     20.2.2.0 [110/2] via 10.1.1.2, 00:01:04, GigabitEthernet2

 

SPFの計算結果の確認

R1の10.1.1.1からR2の20.1.1.2と20.2.2.2へのPingが成功することが確認できます。

R1

R1#ping 20.1.1.2 source 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 20.1.1.2, timeout is 2 seconds:
Packet sent with a source address of 10.1.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms


R1#ping 20.2.2.2 source 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 20.2.2.2, timeout is 2 seconds:
Packet sent with a source address of 10.1.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms

 

not-advertiseオプション有りのrangeコマンド設定後

R2において、OSPFのArea 0にnot-advertiseオプション有りのrangeコマンドを設定し、Area 2からArea 0に対する20.1.1.0/24の広報を禁止します。

追加したOPSFの設定

R2にnot-advertiseオプション有りのrangeコマンドを設定し、Area 2から他のAreaに対して20.1.1.0/24を格納したLSA Type 3の投入を禁止します。

R2

router ospf 1
 area 2 range 20.1.1.0 255.255.255.0 not-advertise

 

OSPFプロセスの状態確認

R2において、Area 2に対してnot-advertiseオプション有りのrangeコマンドが設定されていることが確認できます。

R2

R2#show ip ospf
 Routing Process "ospf 1" with ID 2.2.2.2
 Start time: 1d07h, Time elapsed: 00:26:59.587
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 Supports Link-local Signaling (LLS)
 Supports area transit capability
 Supports NSSA (compatible with RFC 3101)
 Supports Database Exchange Summary List Optimization (RFC 5243)
 Event-log enabled, Maximum number of events: 1000, Mode: cyclic
 It is an area border router
 Router is not originating router-LSAs with maximum metric
 Initial SPF schedule delay 50 msecs
 Minimum hold time between two consecutive SPFs 200 msecs
 Maximum wait time between two consecutive SPFs 5000 msecs
 Incremental-SPF disabled
 Initial LSA throttle delay 50 msecs
 Minimum hold time for LSA throttle 200 msecs
 Maximum wait time for LSA throttle 5000 msecs
 Minimum LSA arrival 100 msecs
 LSA group pacing timer 240 secs
 Interface flood pacing timer 33 msecs
 Retransmission pacing timer 66 msecs
 EXCHANGE/LOADING adjacency limit: initial 300, process maximum 300
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 2. 2 normal 0 stub 0 nssa
 Number of areas transit capable is 0
 External flood list length 0
 IETF NSF helper support enabled
 Cisco NSF helper support enabled
 Reference bandwidth unit is 100 mbps
    Area BACKBONE(0)
        Number of interfaces in this area is 1
        Area has no authentication
        SPF algorithm last executed 00:00:32.557 ago
        SPF algorithm executed 15 times
        Area ranges are
        Number of LSA 3. Checksum Sum 0x016095
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0
    Area 2
        Number of interfaces in this area is 2
        Area has no authentication
        SPF algorithm last executed 00:00:32.557 ago
        SPF algorithm executed 27 times
        Area ranges are
           20.1.1.0/24 Passive DoNotAdvertise
        Number of LSA 2. Checksum Sum 0x00FC08
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0

 

LSDBの状態確認

R2がArea 0に対して20.2.2.0/24を格納したLSA Type 3のみを投入していることが確認できます。

R2

R2#show ip ospf database

            OSPF Router with ID (2.2.2.2) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
1.1.1.1         1.1.1.1         284         0x80000013 0x00BB2C 2
2.2.2.2         2.2.2.2         283         0x80000002 0x008072 2

                Summary Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
20.2.2.0        2.2.2.2         26          0x80000001 0x0024F7

                Router Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum Link count
2.2.2.2         2.2.2.2         220         0x80000004 0x00429C 2

                Summary Net Link States (Area 2)

Link ID         ADV Router      Age         Seq#       Checksum
10.1.1.0        2.2.2.2         283         0x80000001 0x00BD6A0001 0x00BD6A

 

SPFの計算結果の確認

R1はOSPF経由で20.2.2.0/24のみを学習していることが確認できます。

R1

R1#show ip ospf rib

            OSPF Router with ID (1.1.1.1) (Process ID 1)

                Base Topology (MTID 0)

OSPF local RIB
Codes: * - Best, > - Installed in global RIB

*   10.1.1.0/24, Intra, cost 1, area 0, Connected
      via 10.1.1.1, GigabitEthernet2
*>  20.2.2.0/24, Inter, cost 2, area 0
      via 10.1.1.2, GigabitEthernet2

 

SPFの計算結果の確認

R1のルーティングテーブルには20.2.2.0/24のみ投入されていることが確認できます。

R1

R1#show ip route ospf
      20.0.0.0/24 is subnetted, 1 subnets
O IA     20.2.2.0 [110/2] via 10.1.1.2, 00:01:27, GigabitEthernet2

 

SPFの計算結果の確認

R1の10.1.1.1からR2の20.1.1.2へのPingは失敗し、20.2.2.2へのPingが成功することが確認できます。

R1

R1#ping 20.1.1.2 source 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 20.1.1.2, timeout is 2 seconds:
Packet sent with a source address of 10.1.1.1
.....
Success rate is 0 percent (0/5)


R1#ping 20.2.2.2 source 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 20.2.2.2, timeout is 2 seconds:
Packet sent with a source address of 10.1.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms

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