今回はOSPFのLink-Local Signalingについて解説します。
座学
Link-Local Signaling
OSPFが動作しているルータ間で新しい拡張情報をやり取りするため、OSPFパケットの末尾にLLS(Link-Local Signaling)と呼ばれるデータが追加されました。
ルータがLLSをサポートしている場合、OptionフィールドのL(LLS) bitに1がセットされます。
Link-Local Signalingのパケットフォーマット
LLS Data Block
・Checksum
LLS Data Blockのチェックサムが格納されます。
・LLS Data Length
LLS Data Blockのサイズが格納されます。
・LLS TLVs
LLSのTLV(Type-Length-Value)が格納されます。
LLS TLV
・LLS Type
LLS TLVのTypeが格納されます。
・LLS Length
LLS TLVのサイズが格納されます。
・LLS Value
LLS TLVの値が格納されます。
EOF(Extended Options and Flags) TLV
・RS(Restart Signaling) bit
Graceful Restartと呼ばれる機能で使用されます。
・LR(LSDB Resynchronization) bit
OOB(Out-of-Band) LSDB Resynchronizationと呼ばれる機能で使用されます。
Local Interface TLV
・Local Interface ID
Helloパケットの送信元のルータのインタフェースを識別するIDが格納されます。
実機での動作確認
検証内容
R1のg2、R2のg2でOSPF Area 0を有効にします。
Network TypeにはPoint-to-Pointを使用します。
R1が送信するHelloパケットのLLSを確認します。
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
!
router ospf 1
router-id 2.2.2.2
network 10.1.1.0 0.0.0.255 area 0
初期状態
OSPFプロセスの確認
R1のOSPFプロセスでLLSが有効なことが確認できます。
R1
R1#show ip ospf
Routing Process "ospf 1" with ID 1.1.1.1
Start time: 2w1d, Time elapsed: 00:07:51.340
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)
.
<一部省略>
OSPFが動作しているインタフェースの確認
R1のg2でLLSが有効なことが確認できます。
R1
R1#show ip ospf interface
GigabitEthernet2 is up, line protocol is up
Internet Address 10.1.1.1/24, Interface ID 6, Area 0
Attached via Network Statement
Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1
Topology-MTID Cost Disabled Shutdown Topology Name
0 1 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1/1, flood queue length 0
Next 0x0(0)/0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 2.2.2.2
Suppress hello for 0 neighbor(s)
Helloパケットの確認
R1が送信したHelloパケットのL bitに1がセットされていることが確認できます。また、LLS Data Blockが存在することが確認できます。
OSPFネイバーの確認
R2はR1のInterface IDやExtended Optionを認識していることが確認できます。
R1
R2#show ip ospf neighbor detail
Neighbor 1.1.1.1, interface address 10.1.1.1, interface-id 6
In the area 0 via interface GigabitEthernet2
Neighbor priority is 0, State is FULL, 6 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options is 0x12 in Hello (E-bit, L-bit)
Options is 0x52 in DBD (E-bit, L-bit, O-bit)
LLS Options is 0x1 (LR)
Dead timer due in 00:00:35
Neighbor is up for 02:43:28
Index 1/1/1, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec
LLSをグローバル単位で無効化
R1において、グローバル単位でLLSを無効化します。
追加した設定
グローバル単位でのLLSの無効化はno capability llsコマンドで可能です
R1
router ospf 1
no capability lls
OSPFプロセスの確認
R1のOSPFプロセスでLLSが無効なことが確認できます。
R1
R1#show ip ospf
Routing Process "ospf 1" with ID 1.1.1.1
Start time: 2w1d, Time elapsed: 00:07:51.340
Supports only single TOS(TOS0) routes
Supports opaque LSA
Does not supports Link-local Signaling (LLS)
Supports area transit capability
Supports NSSA (compatible with RFC 3101)
Supports Database Exchange Summary List Optimization (RFC 5243)
.
<一部省略>
OSPFが動作しているインタフェースの確認
R1のg2でLLSが無効なことが確認できます。
R1
R1#show ip ospf interface
GigabitEthernet2 is up, line protocol is up
Internet Address 10.1.1.1/24, Interface ID 6, Area 0
Attached via Network Statement
Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1
Topology-MTID Cost Disabled Shutdown Topology Name
0 1 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Does not supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1/1, flood queue length 0
Next 0x0(0)/0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 2.2.2.2
Suppress hello for 0 neighbor(s)
Helloパケットの確認
R1が送信したHelloパケットのL bitに0がセットされていることが確認できます。LLS Data Blockが存在しないことが確認できます。
OSPFネイバーの確認
R1のg2でLLSが無効なため、R2はR1のInterface IDやExtended Optionを認識していないことが確認できます。
R1
R2#show ip ospf neighbor detail
Neighbor 1.1.1.1, interface address 10.1.1.1
In the area 0 via interface GigabitEthernet2
Neighbor priority is 0, State is FULL, 12 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options is 0x2 in Hello (E-bit)
Options is 0x42 in DBD (E-bit, O-bit)
Dead timer due in 00:00:32
Neighbor is up for 00:01:05
Index 1/1/1, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec
LLSをグローバル単位で無効化 , インタフェース単位で有効化
R1において、グローバル単位でLLSを無効化し、かつ、g2でLLSを有効化します。
追加した設定
インタフェース単位でのLLSの有効化はip ospf llsコマンドで可能です。
R1
router ospf 1
no capability lls
!
interface GigabitEthernet2
ip ospf lls
OSPFプロセスの確認
R1のOSPFプロセスでLLSが無効なことが確認できます。
R1
R1#show ip ospf
Routing Process "ospf 1" with ID 1.1.1.1
Start time: 2w1d, Time elapsed: 00:07:51.340
Supports only single TOS(TOS0) routes
Supports opaque LSA
Does not supports Link-local Signaling (LLS)
Supports area transit capability
Supports NSSA (compatible with RFC 3101)
Supports Database Exchange Summary List Optimization (RFC 5243)
.
<一部省略>
OSPFが動作しているインタフェースの確認
R1のg2でLLSが有効なことが確認できます。
R1
R1#show ip ospf interface
GigabitEthernet2 is up, line protocol is up
Internet Address 10.1.1.1/24, Interface ID 6, Area 0
Attached via Network Statement
Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1
Topology-MTID Cost Disabled Shutdown Topology Name
0 1 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1/1, flood queue length 0
Next 0x0(0)/0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 2.2.2.2
Suppress hello for 0 neighbor(s)
OSPFネイバーの確認
R2はR1のInterface IDやExtended Optionを認識していることが確認できます。
R1
R2#show ip ospf neighbor detail
Neighbor 1.1.1.1, interface address 10.1.1.1, interface-id 6
In the area 0 via interface GigabitEthernet2
Neighbor priority is 0, State is FULL, 6 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options is 0x12 in Hello (E-bit, L-bit)
Options is 0x52 in DBD (E-bit, L-bit, O-bit)
LLS Options is 0x1 (LR)
Dead timer due in 00:00:35
Neighbor is up for 02:43:28
Index 1/1/1, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec
LLSをインタフェース単位で無効化
R1において、g2でLLSを無効化します。
追加した設定
インタフェース単位でのLLSの無効化はip ospf lls disableコマンドで可能です。
R1
interface GigabitEthernet2
ip ospf lls disable
OSPFプロセスの確認
R1のOSPFプロセスでLLSが有効なことが確認できます。
R1
R1#show ip ospf
Routing Process "ospf 1" with ID 1.1.1.1
Start time: 2w1d, Time elapsed: 00:07:51.340
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)
.
<一部省略>
OSPFが動作しているインタフェースの確認
R1のg2でLLSが無効なことが確認できます。
R1
R1#show ip ospf interface
GigabitEthernet2 is up, line protocol is up
Internet Address 10.1.1.1/24, Interface ID 6, Area 0
Attached via Network Statement
Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1
Topology-MTID Cost Disabled Shutdown Topology Name
0 1 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Does not supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1/1, flood queue length 0
Next 0x0(0)/0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 2.2.2.2
Suppress hello for 0 neighbor(s)
OSPFネイバーの確認
R1のg2でLLSが無効なため、R2はR1のInterface IDやExtended Optionを認識していないことが確認できます。
R1
R2#show ip ospf neighbor detail
Neighbor 1.1.1.1, interface address 10.1.1.1
In the area 0 via interface GigabitEthernet2
Neighbor priority is 0, State is FULL, 12 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options is 0x2 in Hello (E-bit)
Options is 0x42 in DBD (E-bit, O-bit)
Dead timer due in 00:00:32
Neighbor is up for 00:01:05
Index 1/1/1, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec
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