今回はDisjoint Pathを使用して、既に計算済みのLSPが使用中のリンクと同じSRLGに所属しているリンクを経由しないように、新規のLSPを計算する方法を説明しました。
この記事の目次
概要
SRLGについて
以下の図で、R3で筐体障害が発生した場合、R2のg3とg4のリンクが同時にダウンします。
このように、何か障害が発生した際に、同時に影響を受けるリンクのグループをSRLG(Shared Risk Link Group)と呼びます。
OSPFやIS-ISでは、リンクが所属するSRLGの情報を広報可能です。
以下はOSPFのSRLG用のSub-TLVのフォーマットになります。
以下はIS-ISのSRLG用のSub-TLVのフォーマットになります。
SRLG TypeのDisjoint Pathについて
Disjoint Pathではリンクとノードに加えて、既に計算済みのLSPが使用中のリンクと同じSRLGに所属しているリンクを経由しないように、新規のLSPを計算可能です。
検証内容と設定
基本設定の内容
R1-R2-R3-R4-R5-R6-R7間でOSPF Area 0を構成します。
OSPFでSR-TEを有効にします。
R3-R4間の10.4.4.0/24のリンクのコストを30、10.5.5.0/24のリンクのコストを50に変更します。
R3のg0/0/0/2とg0/0/0/3にSRLGとして77を割り当てます。
R1でLoopback Interfaceの1.1.1.1/32にPrefix SIDとして20101を割り当てます。
R3でLoopback Interfaceの2.2.2.2/32にPrefix SIDとして20201を割り当てます。
R3でLoopback Interfaceの3.3.3.3/32にPrefix SIDとして20301を割り当てます。
R4でLoopback Interfaceの4.4.4.4/32にPrefix SIDとして20401を割り当てます。
R5でLoopback Interfaceの5.5.5.5/32にPrefix SIDとして20501を割り当てます。
R6でLoopback Interfaceの6.6.6.6/32にPrefix SIDとして20601を割り当てます。
R7でLoopback Interfaceの7.7.7.7/32にPrefix SIDとして20701を割り当てます。
R7をPCE、R1とR2をPCCとして動作させます。
初期設定
interface Loopback0
ipv4 address 1.1.1.1 255.255.255.255
!
interface GigabitEthernet0/0/0/0
ipv4 address 10.1.1.1 255.255.255.0
!
interface GigabitEthernet0/0/0/1
ipv4 address 10.8.8.1 255.255.255.0
!
router ospf 1
router-id 1.1.1.1
segment-routing mpls
area 0
mpls traffic-eng
interface Loopback0
prefix-sid absolute 20101
!
interface GigabitEthernet0/0/0/0
network point-to-point
!
interface GigabitEthernet0/0/0/1
network point-to-point
!
!
!
segment-routing
traffic-eng
pcc
pce address ipv4 7.7.7.7
interface Loopback0
ipv4 address 2.2.2.2 255.255.255.255
!
interface GigabitEthernet0/0/0/0
ipv4 address 10.2.2.2 255.255.255.0
!
interface GigabitEthernet0/0/0/1
ipv4 address 10.9.9.2 255.255.255.0
!
router ospf 1
router-id 2.2.2.2
segment-routing mpls
area 0
mpls traffic-eng
interface Loopback0
prefix-sid absolute 20201
!
interface GigabitEthernet0/0/0/0
network point-to-point
!
interface GigabitEthernet0/0/0/1
network point-to-point
!
!
!
segment-routing
traffic-eng
pcc
pce address ipv4 7.7.7.7
srlg
interface GigabitEthernet0/0/0/2
name SRLG_1
!
interface GigabitEthernet0/0/0/3
name SRLG_1
!
name SRLG_1 value 77
!
interface Loopback0
ipv4 address 3.3.3.3 255.255.255.0
!
interface GigabitEthernet0/0/0/0
ipv4 address 10.1.1.3 255.255.255.0
!
interface GigabitEthernet0/0/0/1
ipv4 address 10.2.2.3 255.255.255.0
!
interface GigabitEthernet0/0/0/2
ipv4 address 10.3.3.3 255.255.255.0
!
interface GigabitEthernet0/0/0/3
ipv4 address 10.4.4.3 255.255.255.0
!
interface GigabitEthernet0/0/0/4
ipv4 address 10.5.5.3 255.255.255.0
!
router ospf 1
router-id 3.3.3.3
segment-routing mpls
area 0
mpls traffic-eng
interface Loopback0
prefix-sid absolute 20301
!
interface GigabitEthernet0/0/0/0
network point-to-point
!
interface GigabitEthernet0/0/0/1
network point-to-point
!
interface GigabitEthernet0/0/0/2
network point-to-point
!
interface GigabitEthernet0/0/0/3
cost 30
network point-to-point
!
interface GigabitEthernet0/0/0/4
cost 50
network point-to-point
!
!
!
segment-routing
traffic-eng
interface Loopback0
ipv4 address 4.4.4.4 255.255.255.255
!
interface GigabitEthernet0/0/0/0
ipv4 address 10.6.6.4 255.255.255.0
!
interface GigabitEthernet0/0/0/1
ipv4 address 10.7.7.4 255.255.255.0
!
interface GigabitEthernet0/0/0/2
ipv4 address 10.3.3.4 255.255.255.0
!
interface GigabitEthernet0/0/0/3
ipv4 address 10.4.4.4 255.255.255.0
!
interface GigabitEthernet0/0/0/4
ipv4 address 10.5.5.4 255.255.255.0
!
router ospf 1
router-id 4.4.4.4
segment-routing mpls
area 0
mpls traffic-eng
interface Loopback0
prefix-sid absolute 20401
!
interface GigabitEthernet0/0/0/0
network point-to-point
!
interface GigabitEthernet0/0/0/1
network point-to-point
!
interface GigabitEthernet0/0/0/2
network point-to-point
!
interface GigabitEthernet0/0/0/3
cost 30
network point-to-point
!
interface GigabitEthernet0/0/0/4
cost 50
network point-to-point
!
!
!
segment-routing
traffic-eng
interface Loopback0
ipv4 address 5.5.5.5 255.255.255.255
!
interface GigabitEthernet0/0/0/0
ipv4 address 10.6.6.5 255.255.255.0
!
router ospf 1
router-id 5.5.5.5
segment-routing mpls
area 0
mpls traffic-eng
interface Loopback0
prefix-sid absolute 20501
!
interface GigabitEthernet0/0/0/0
network point-to-point
!
!
!
segment-routing
traffic-eng
interface Loopback0
ipv4 address 6.6.6.6 255.255.255.255
!
interface GigabitEthernet0/0/0/0
ipv4 address 10.7.7.6 255.255.255.0
!
router ospf 1
router-id 6.6.6.6
segment-routing mpls
area 0
mpls traffic-eng
interface Loopback0
prefix-sid absolute 20601
!
interface GigabitEthernet0/0/0/0
network point-to-point
!
!
!
segment-routing
traffic-eng
pce
address ipv4 7.7.7.7
!
interface Loopback0
ipv4 address 7.7.7.7 255.255.255.255
!
interface GigabitEthernet0/0/0/0
ipv4 address 10.8.8.7 255.255.255.0
!
interface GigabitEthernet0/0/0/1
ipv4 address 10.9.9.7 255.255.255.0
!
router ospf 1
distribute link-state
router-id 7.7.7.7
segment-routing mpls
area 0
mpls traffic-eng
interface Loopback0
prefix-sid absolute 20701
!
interface GigabitEthernet0/0/0/0
network point-to-point
!
interface GigabitEthernet0/0/0/1
network point-to-point
!
!
!
segment-routing
traffic-eng
SRLGの設定と状態確認
SRLGの設定
最初にname <srlg-name> value <srlg-value>コマンドを使用してSRLGの名前と値を定義します。そして、インタフェースに対して、name <srlg-name>コマンドを設定し、SRLGを割り当てます。
R3
srlg
interface GigabitEthernet0/0/0/2
name SRLG_1
!
interface GigabitEthernet0/0/0/3
name SRLG_1
!
name SRLG_1 value 77
SRLGの状態確認
インタフェースに割り当てられたSRLGはshow srlgコマンドで確認可能です。
R3
RP/0/RP0/CPU0:R3#show srlg
System Information::
Interface Count : 5 (Maximum Interfaces Supported 512)
Group Count : 0 (Maximum Groups Supported 50)
Inherit Location Count : 0 (Maximum Inherit Locations Supported 10)
Optical Interfaces Count : 0 (Maximum Optical Interfaces Supported 500)
Interface : GigabitEthernet0/0/0/0, Value Count : 0
References : 2, Internal flags : 0x2
Interface : GigabitEthernet0/0/0/1, Value Count : 0
References : 2, Internal flags : 0x2
Interface : GigabitEthernet0/0/0/2, Value Count : 1
References : 3, Internal flags : 0x3
SRLG Values : 77
Interface : GigabitEthernet0/0/0/3, Value Count : 1
References : 3, Internal flags : 0x3
SRLG Values : 77
Interface : GigabitEthernet0/0/0/4, Value Count : 0
References : 2, Internal flags : 0x2
OSPFの状態確認
R3のg0/0/0/2のOSPFの状態を見ると、OSPFがSRLGを認識していることが確認できます。
R3
RP/0/RP0/CPU0:R3#show ospf interface GigabitEthernet0/0/0/2
GigabitEthernet0/0/0/2 is up, line protocol is up
Internet Address 10.3.3.3/24, Area 0, SID 0, Strict-SPF SID 0
Label stack Primary label 1 Backup label 3 SRTE label 10
Process ID 1, Router ID 3.3.3.3, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT, MTU 1500, MaxPktSz 1500
Forward reference No, Unnumbered no, Bandwidth 1000000
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:09:323
Index 4/4, flood queue length 0
Next 0(0)/0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
LS Ack List: current length 0, high water mark 6
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 4.4.4.4
Suppress hello for 0 neighbor(s)
Multi-area interface Count is 0
SRLG values:
77
R3の10.3.3.0/24のリンクのMPLS Traffic Engineering LSAを見ると、SRLGが格納されていることが確認できます。
R3
RP/0/RP0/CPU0:R3#show ospf database opaque-area 1.0.0.9 adv-router 3.3.3.3
OSPF Router with ID (3.3.3.3) (Process ID 1)
Type-10 Opaque Link Area Link States (Area 0)
LS age: 508
Options: (No TOS-capability, DC)
LS Type: Opaque Area Link
Link State ID: 1.0.0.9
Opaque Type: 1
Opaque ID: 9
Advertising Router: 3.3.3.3
LS Seq Number: 80000002
Checksum: 0xde91
Length: 212
Link connected to Point-to-Point network
Link ID : 4.4.4.4
(all bandwidths in bytes/sec)
Interface Address : 10.3.3.3
Neighbor Address : 10.3.3.4
Admin Metric : 1
Maximum bandwidth : 125000000
Maximum reservable bandwidth global: 0
Number of Priority : 8
Priority 0 : 0 Priority 1 : 0
Priority 2 : 0 Priority 3 : 0
Priority 4 : 0 Priority 5 : 0
Priority 6 : 0 Priority 7 : 0
Affinity Bit : 0
IGP Metric : 1
GMPLS Shared Risked Link Group : Length: 4
Number of SRLGs (1)
[1]: 77
Extended Administrative Group : Length: 8
EAG[0]: 0
EAG[1]: 0
EAG[2]: 0
EAG[3]: 0
EAG[4]: 0
EAG[5]: 0
EAG[6]: 0
EAG[7]: 0
Number of Links : 1
以下はR3の10.3.3.0/24のリンクのMPLS Traffic Engineering LSAのキャプチャになります。SRLGが格納されていることが確認できます。
SR-TE DBの状態確認
R7のSR-TE DB内を見ると、R3の10.3.3.0/24と10.4.4.0/24のリンクにSRLGが割り当てられていることが確認できます。
R3
RP/0/RP0/CPU0:R7#show pce ipv4 topology traffic-eng 3.3.3.3
PCE's topology database - detail:
---------------------------------
Node 2
.
<一部省略>
.
Link[2]: local address 10.3.3.3, remote address 10.3.3.4
Local node:
OSPF router ID: 3.3.3.3 area ID: 0 ASN: 0
Remote node:
TE router ID: 4.4.4.4
OSPF router ID: 4.4.4.4 area ID: 0 ASN: 0
Metric: IGP 1, TE 1, Latency 1 microseconds
Bandwidth: Total 125000000 Bps, Reservable 0 Bps
Admin-groups: 0x00000000
Adj SID: 24002 (unprotected)
SRLG Values: 77
Link[3]: local address 10.4.4.3, remote address 10.4.4.4
Local node:
OSPF router ID: 3.3.3.3 area ID: 0 ASN: 0
Remote node:
TE router ID: 4.4.4.4
OSPF router ID: 4.4.4.4 area ID: 0 ASN: 0
Metric: IGP 30, TE 30, Latency 30 microseconds
Bandwidth: Total 125000000 Bps, Reservable 0 Bps
Admin-groups: 0x00000000
Adj SID: 24003 (unprotected)
SRLG Values: 77
.
<一部省略>
Disjoint Group設定無し
SR-TE Policyの設定
R1でEnd-pointに5.5.5.5、R2でEnd-pointに6.6.6.6を指定したSR-TE Policyを設定し、PCEにLSPの計算を依頼します。ただし、Disjoint Groupは設定しません。
R1
segment-routing
traffic-eng
policy SR-TE_POLICY
color 1 end-point ipv4 5.5.5.5
autoroute
include all
!
candidate-paths
preference 10
dynamic
pcep
R2
segment-routing
traffic-eng
policy SR-TE_POLICY
color 1 end-point ipv4 6.6.6.6
autoroute
include all
!
candidate-paths
preference 10
dynamic
pcep
PCEが計算したLSPの確認
R7が計算したR1とR2のLSPを見ると、両方とも、R3-R4間の10.3.3.0/24のリンクを経由していることが確認できます。
R7
RP/0/RP0/CPU0:R7#show pce lsp pcc ipv4 1.1.1.1 detail
PCE's tunnel database:
----------------------
PCC 1.1.1.1:
Tunnel Name: cfg_SR-TE_POLICY_discr_10
Color: 1
Interface Name: srte_c_1_ep_5.5.5.5
LSPs:
LSP[0]:
source 1.1.1.1, destination 5.5.5.5, tunnel ID 1, LSP ID 1
State: Admin up, Operation up
Setup type: Segment Routing
Binding SID: 24006
Maximum SID Depth: 10
Preference: 10
Bandwidth: signaled 0 kbps, applied 0 kbps
PCEP information:
PLSP-ID 0x1, flags: D:1 S:0 R:0 A:1 O:1 C:0
LSP Role: Single LSP
State-sync PCE: None
PCC: 1.1.1.1
LSP is subdelegated to: None
Reported path:
Metric type: TE, Accumulated Metric 3
SID[0]: Node, Label 20501, Address 5.5.5.5
Computed path: (Local PCE)
Computed Time: Sat Jun 27 19:46:14 UTC 2020 (00:02:01 ago)
Metric type: TE, Accumulated Metric 3
SID[0]: Node, Label 20501, Address 5.5.5.5
Recorded path:
None
Disjoint Group Information:
None
R7
RP/0/RP0/CPU0:R7#show pce lsp pcc ipv4 2.2.2.2 detail
PCE's tunnel database:
----------------------
PCC 2.2.2.2:
Tunnel Name: cfg_SR-TE_POLICY_discr_10
Color: 1
Interface Name: srte_c_1_ep_6.6.6.6
LSPs:
LSP[0]:
source 2.2.2.2, destination 6.6.6.6, tunnel ID 1, LSP ID 1
State: Admin up, Operation up
Setup type: Segment Routing
Binding SID: 24006
Maximum SID Depth: 10
Preference: 10
Bandwidth: signaled 0 kbps, applied 0 kbps
PCEP information:
PLSP-ID 0x1, flags: D:1 S:0 R:0 A:1 O:1 C:0
LSP Role: Single LSP
State-sync PCE: None
PCC: 2.2.2.2
LSP is subdelegated to: None
Reported path:
Metric type: TE, Accumulated Metric 3
SID[0]: Node, Label 20601, Address 6.6.6.6
Computed path: (Local PCE)
Computed Time: Sat Jun 27 19:46:24 UTC 2020 (00:02:25 ago)
Metric type: TE, Accumulated Metric 3
SID[0]: Node, Label 20601, Address 6.6.6.6
Recorded path:
None
Disjoint Group Information:
None
疎通確認
R1の1.1.1.1からR5の5.5.5.5へTracerouteを実施します。
R1からR5へのトラフィックがR3-R4間の10.3.3.0/24のリンクを経由していることが確認できます。
R1
RP/0/RP0/CPU0:R1#traceroute 5.5.5.5 source 1.1.1.1
Type escape sequence to abort.
Tracing the route to 5.5.5.5
1 10.1.1.3 [MPLS: Label 20501 Exp 0] 116 msec 127 msec 104 msec
2 10.3.3.4 [MPLS: Label 20501 Exp 0] 100 msec 96 msec 87 msec
3 10.6.6.5 100 msec * 123 msec
R2の2.2.2.2からR6の6.6.6.6へTracerouteを実施します。
R2からR6へのトラフィックがR3-R4間の10.3.3.0/24のリンクを経由していることが確認できます。
R2
RP/0/RP0/CPU0:R2#traceroute 6.6.6.6 source 2.2.2.2
Type escape sequence to abort.
Tracing the route to 6.6.6.6
1 10.2.2.3 [MPLS: Label 20601 Exp 0] 198 msec 119 msec 158 msec
2 10.3.3.4 [MPLS: Label 20601 Exp 0] 150 msec 147 msec 142 msec
3 10.7.7.6 168 msec * 170 msec
Disjoint Group設定有り
SR-TE Policyの設定
同じSRLGに属するリンクを経由させないDisjoint Groupはdisjoint-path group-id <group-id> type srlgコマンドで設定します。
R1
segment-routing
traffic-eng
policy SR-TE_POLICY
color 1 end-point ipv4 5.5.5.5
autoroute
include all
!
candidate-paths
preference 10
dynamic
pcep
!
!
constraints
disjoint-path group-id 1 type srlg
R2
segment-routing
traffic-eng
policy SR-TE_POLICY
color 1 end-point ipv4 6.6.6.6
autoroute
include all
!
candidate-paths
preference 10
dynamic
pcep
!
!
constraints
disjoint-path group-id 1 type srlg
PCEが計算したLSPの確認
R7が計算したR1とR2のLSPを見ると、R1のLSPはR3-R4間の10.3.3.0/24のリンク、R2のLSPはR3-R4間の10.5.5.0/24のリンクを経由していることが確認できます。
R7
RP/0/RP0/CPU0:R7#show pce lsp pcc ipv4 1.1.1.1 detail
PCE's tunnel database:
----------------------
PCC 1.1.1.1:
Tunnel Name: cfg_SR-TE_POLICY_discr_10
Color: 1
Interface Name: srte_c_1_ep_5.5.5.5
LSPs:
LSP[0]:
source 1.1.1.1, destination 5.5.5.5, tunnel ID 6, LSP ID 1
State: Admin up, Operation up
Setup type: Segment Routing
Binding SID: 24021
Maximum SID Depth: 10
Preference: 10
Bandwidth: signaled 0 kbps, applied 0 kbps
PCEP information:
PLSP-ID 0x6, flags: D:1 S:0 R:0 A:1 O:1 C:0
LSP Role: Exclude LSP
State-sync PCE: None
PCC: 1.1.1.1
LSP is subdelegated to: None
Reported path:
Metric type: TE, Accumulated Metric 3
SID[0]: Node, Label 20501, Address 5.5.5.5
Computed path: (Local PCE)
Computed Time: Sat Jun 27 20:49:48 UTC 2020 (00:00:12 ago)
Metric type: TE, Accumulated Metric 3
SID[0]: Node, Label 20501, Address 5.5.5.5
Recorded path:
None
Disjoint Group Information:
Type SRLG-Disjoint, Group 1
R7
RP/0/RP0/CPU0:R7#show pce lsp pcc ipv4 2.2.2.2 detail
PCE's tunnel database:
----------------------
PCC 2.2.2.2:
Tunnel Name: cfg_SR-TE_POLICY_discr_10
Color: 1
Interface Name: srte_c_1_ep_6.6.6.6
LSPs:
LSP[0]:
source 2.2.2.2, destination 6.6.6.6, tunnel ID 6, LSP ID 1
State: Admin up, Operation up
Setup type: Segment Routing
Binding SID: 24016
Maximum SID Depth: 10
Preference: 10
Bandwidth: signaled 0 kbps, applied 0 kbps
PCEP information:
PLSP-ID 0x6, flags: D:1 S:0 R:0 A:1 O:1 C:0
LSP Role: Disjoint LSP
State-sync PCE: None
PCC: 2.2.2.2
LSP is subdelegated to: None
Reported path:
Metric type: TE, Accumulated Metric 52
SID[0]: Node, Label 20301, Address 3.3.3.3
SID[1]: Adj, Label 24004, Address: local 10.5.5.3 remote 10.5.5.4
SID[2]: Node, Label 20601, Address 6.6.6.6
Computed path: (Local PCE)
Computed Time: Sat Jun 27 20:49:48 UTC 2020 (00:00:23 ago)
Metric type: TE, Accumulated Metric 52
SID[0]: Node, Label 20301, Address 3.3.3.3
SID[1]: Adj, Label 24004, Address: local 10.5.5.3 remote 10.5.5.4
SID[2]: Node, Label 20601, Address 6.6.6.6
Recorded path:
None
Disjoint Group Information:
Type SRLG-Disjoint, Group 1
疎通確認
R1の1.1.1.1からR5の5.5.5.5へTracerouteを実施します。
R1からR5へのトラフィックがR3-R4間の10.3.3.0/24のリンクを経由していることが確認できます。
R1
RP/0/RP0/CPU0:R1#traceroute 5.5.5.5 source 1.1.1.1
Type escape sequence to abort.
Tracing the route to 5.5.5.5
1 10.1.1.3 [MPLS: Label 20501 Exp 0] 116 msec 127 msec 104 msec
2 10.3.3.4 [MPLS: Label 20501 Exp 0] 100 msec 96 msec 87 msec
3 10.6.6.5 100 msec * 123 msec
R2の2.2.2.2からR6の6.6.6.6へTracerouteを実施します。
R2からR6へのトラフィックがR3-R4間の10.5.5.0/24のリンクを経由していることが確認できます。
R2
RP/0/RP0/CPU0:R2#traceroute 6.6.6.6 source 2.2.2.2
Type escape sequence to abort.
Tracing the route to 6.6.6.6
1 10.2.2.3 [MPLS: Labels 24004/20601 Exp 0] 84 msec 87 msec 105 msec
2 10.5.5.4 [MPLS: Label 20601 Exp 0] 131 msec 106 msec 163 msec
3 10.7.7.6 98 msec * 72 msec
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