SRLG - это функционал, позволяющий предотвратить построение основного и резервного LSP через линии, которые могут выйти из строя одновременно, например, 2 волокна находящиеся в одном кабеле.
В качетсве примера, сконфигурируем туннель R1-R2 и добавим возможность построения резервного туннеля (End-to-End protection).
Конфигурация R1:
interface loopback 1
ipv4 address 1.1.1.1/32
exit
interface tengigabitethernet 0/0/2
description R2
ipv4 address 172.1.0.1/30
exit
interface tengigabitethernet 0/0/3
description R3
ipv4 address 172.4.0.1/30
exit
interface tengigabitethernet 0/0/4.2
description R4
encapsulation outer-vid 2
ipv4 address 172.0.0.5/30
exit
interface tengigabitethernet 0/0/4.3
description R4
encapsulation outer-vid 3
ipv4 address 172.0.0.1/30
exit
mpls
forwarding
interface loopback 1
interface tengigabitethernet 0/0/2
interface tengigabitethernet 0/0/3
interface tengigabitethernet 0/0/4.2
interface tengigabitethernet 0/0/4.3
exit
router-id 1.1.1.1
rsvp
interface tengigabitethernet 0/0/2
exit
interface tengigabitethernet 0/0/3
te-metric 50
exit
interface tengigabitethernet 0/0/4.2
exit
interface tengigabitethernet 0/0/4.3
exit
srlg SRLG
group-id 100
exit
tunnel to_R2
destination 2.2.2.2
end-to-end
protection-type 1-to-1
exit
record-route
source 1.1.1.1
tunnel-lsp primary
exit
tunnel-lsp backup
end-to-end backup
exit
exit
exit
exit
exit
router ospfv2 0
area 0.0.0.0
interface loopback 1
passive
exit
interface tengigabitethernet 0/0/2
bfd fast-detect
network point-to-point
te-support
exit
interface tengigabitethernet 0/0/3
bfd fast-detect
network point-to-point
te-support
exit
interface tengigabitethernet 0/0/4.2
bfd fast-detect
network point-to-point
te-support
exit
interface tengigabitethernet 0/0/4.3
bfd fast-detect
network point-to-point
te-support
exit
exit
router-id 1.1.1.1
te-router-id 1.1.1.1
exit
Конфигурация R2:
interface loopback 1
ipv4 address 2.2.2.2/32
exit
interface tengigabitethernet 0/0/1
description R1
ipv4 address 172.1.0.2/30
exit
interface tengigabitethernet 0/0/3
description R3
ipv4 address 172.5.0.2/30
exit
interface tengigabitethernet 0/0/4
description R4
ipv4 address 172.2.0.2/30
exit
mpls
forwarding
interface loopback 1
interface tengigabitethernet 0/0/1
interface tengigabitethernet 0/0/3
interface tengigabitethernet 0/0/4
exit
router-id 2.2.2.2
rsvp
interface tengigabitethernet 0/0/1
exit
interface tengigabitethernet 0/0/3
exit
interface tengigabitethernet 0/0/4
exit
srlg SRLG
group-id 100
exit
router ospfv2 0
area 0.0.0.0
interface loopback 1
passive
exit
interface tengigabitethernet 0/0/1
bfd fast-detect
network point-to-point
te-support
exit
interface tengigabitethernet 0/0/3
bfd fast-detect
network point-to-point
te-support
exit
interface tengigabitethernet 0/0/4
bfd fast-detect
network point-to-point
te-support
exit
exit
router-id 2.2.2.2
te-router-id 2.2.2.2
exit
Конфигурация R3:
interface loopback 1
ipv4 address 3.3.3.3/32
exit
interface tengigabitethernet 0/0/1
description R1
ipv4 address 172.4.0.2/30
exit
interface tengigabitethernet 0/0/2
description R2
ipv4 address 172.5.0.1/30
exit
mpls
forwarding
interface loopback 1
interface tengigabitethernet 0/0/1
interface tengigabitethernet 0/0/2
exit
rsvp
interface tengigabitethernet 0/0/1
te-metric 50
exit
interface tengigabitethernet 0/0/2
te-metric 50
exit
srlg SRLG
group-id 100
exit
exit
exit
router ospfv2 0
area 0.0.0.0
interface loopback 1
passive
exit
interface tengigabitethernet 0/0/1
bfd fast-detect
network point-to-point
te-support
exit
interface tengigabitethernet 0/0/2
bfd fast-detect
network point-to-point
te-support
exit
exit
router-id 3.3.3.3
te-router-id 3.3.3.3
exit
Конфигурация R4:
interface loopback 1
ipv4 address 4.4.4.4/32
exit
interface tengigabitethernet 0/0/2
description R2
ipv4 address 172.2.0.1/30
exit
interface tengigabitethernet 0/0/1.2
description R1
encapsulation outer-vid 2
ipv4 address 172.0.0.6/30
exit
interface tengigabitethernet 0/0/1.3
description R1
encapsulation outer-vid 3
ipv4 address 172.0.0.2/30
exit
mpls
forwarding
interface loopback 1
interface tengigabitethernet 0/0/2
interface tengigabitethernet 0/0/1.2
interface tengigabitethernet 0/0/1.3
exit
rsvp
interface tengigabitethernet 0/0/2
exit
interface tengigabitethernet 0/0/1.2
exit
interface tengigabitethernet 0/0/1.3
exit
srlg SRLG
group-id 100
exit
exit
exit
router ospfv2 0
area 0.0.0.0
interface loopback 1
passive
exit
interface tengigabitethernet 0/0/2
bfd fast-detect
network point-to-point
te-support
exit
interface tengigabitethernet 0/0/1.2
bfd fast-detect
network point-to-point
te-support
exit
interface tengigabitethernet 0/0/1.3
bfd fast-detect
network point-to-point
te-support
exit
exit
router-id 4.4.4.4
te-router-id 4.4.4.4
exit
Согласно приведенной ниже схеме сконфигурируем на интерфейсах SRLG и посмотрим на построение primary и backup LSP.
Конфигурация R1:
0/ME5100:R1# show running-config mpls rsvp
mpls
rsvp
interface tengigabitethernet 0/0/2
srlg SRLG
exit
interface tengigabitethernet 0/0/3
te-metric 50
exit
interface tengigabitethernet 0/0/4.2
srlg SRLG
exit
interface tengigabitethernet 0/0/4.3
exit
srlg SRLG
group-id 100
exit
Данной конфигурацией мы сообщили, что интерфейсы te0/0/2, te0/0/4.2 имеют одну группу риска. Тем самым, информация о SRLG распространяется посредством IGP и формируется TEDB. Далее CSPF учитывает эту информацию при построении LSP.
Проверим командой show ospfv2 database opaque-area detailed, на примере te0/0/4.2, как распространение информации о SRLG.
show ospfv2 database opaque-area detailed
0/ME5100:R1# show ospfv2 database opaque-area detailed
Area: 0.0.0.0
LSA ID: 1.0.0.9
Router-id: 1.1.1.1
Age: 00:12:10
Seq#: 0x80000004
Checksum: 0x2c26
Type: area-opaque-lsa
Options: E
LSA type: Area-local "opaque" LSA
Length: 152
Opaque Type: Traffic Engineering LSA (1)
Opaque ID: 9
TLV Type : 2 - Link Information
TLV Length: 128
TLV Type: 1 - Link Type
TLV Length: 1
MPLS/TE Link Type: 1
TLV Type: 2 - Link ID
TLV Length: 4
MPLS/TE Link ID: 4.4.4.4
TLV Type: 3 - Local Interface IP Address
TLV Length: 4
MPLS/TE Local Interface Address: 172.0.0.5
TLV Type: 4 - Remote Interface IP Address
TLV Length: 4
MPLS/TE Remote Interface Address: 172.0.0.6
TLV Type: 5 - Traffic Engineering Metric
TLV Length: 4
Traffic Engineering Metric: 1
TLV Type: 6 - Maximum Bandwidth
TLV Length: 4
Maximum Bandwidth: 1250000000 bytes/s
TLV Type: 7 - Maximum Reservable
TLV Length: 4
Maximum Reservable: 1250000000 bytes/s
TLV Type: 8 - Unreserved Bandwidth
TLV Length: 32
Pri (or TE-Class) 0: 1250000000 bytes/s
Pri (or TE-Class) 1: 1250000000 bytes/s
Pri (or TE-Class) 2: 1250000000 bytes/s
Pri (or TE-Class) 3: 1250000000 bytes/s
Pri (or TE-Class) 4: 1250000000 bytes/s
Pri (or TE-Class) 5: 1250000000 bytes/s
Pri (or TE-Class) 6: 1250000000 bytes/s
Pri (or TE-Class) 7: 1250000000 bytes/s
TLV Type: 9 - Resource Class/Color
TLV Length: 4
MPLS/TE Link Resource Class/Color: 0x00000000
TLV Type: 11 - Link Local/Remote Identifiers
TLV Length: 8
Link Local Identifier: 8804
Link Remote Identifier: 46
TLV Type: 14 - Link Protection Type
TLV Length: 4
Protection Capabilities: 0x02
Unprotected
TLV Type: 16 - Shared Risk Link Group
TLV Length: 4
SRLG(s):
100 <<<<< Информация о SRLG
Далее, проверим вывод show mpls te topology о информации содержащийся в TEDB.
show mpls te topology
0/ME5100:R1# show mpls te topology
IGP: 1.1.1.1 (ospfv2)
Area: 0.0.0.0, LSID: 1.0.0.2
Link type: point-to-point, Neighbor Router ID: 2.2.2.2
Local Interface IP address(es):
172.1.0.1
Remote Interface IP address(es):
172.1.0.2
Color/Resource class: 0x0
TE metric: 1
SRLGs:
100 <<<<< Информация о SRLG
Max bandwidth: 10000.00 Mbps, max reservable bandwidth: 10000.00 Mbps
Priority Reservable Bandwidth
---------- ---------------------
0 10000.00 Mbps
1 10000.00 Mbps
2 10000.00 Mbps
3 10000.00 Mbps
4 10000.00 Mbps
5 10000.00 Mbps
6 10000.00 Mbps
7 10000.00 Mbps
IGP: 1.1.1.1 (ospfv2)
Area: 0.0.0.0, LSID: 1.0.0.9
Link type: point-to-point, Neighbor Router ID: 4.4.4.4
Local Interface IP address(es):
172.0.0.5
Remote Interface IP address(es):
172.0.0.6
Color/Resource class: 0x0
TE metric: 1
SRLGs:
100 <<<<< Информация о SRLG
Max bandwidth: 10000.00 Mbps, max reservable bandwidth: 10000.00 Mbps
Priority Reservable Bandwidth
---------- ---------------------
0 10000.00 Mbps
1 10000.00 Mbps
2 10000.00 Mbps
3 10000.00 Mbps
4 10000.00 Mbps
5 10000.00 Mbps
6 10000.00 Mbps
7 10000.00 Mbps
Проверим путь построения primary и backup LSP:
Построение основного и резервного LSP:
0/ME5100:R1# show mpls rsvp lsps tunnel to_R2
Wed Oct 25 07:27:00 2023
Tunnel: to_R2, id: 1
LSP name: primary, signaled-name: to_R2@primary, id: 1, Source: 1.1.1.1, Destination: 2.2.2.2
State: up, Status: active, Protection role: working
Direction: ingress, Node protect: disabled, Bandwidth protection requirement: disabled
Carrying the normal traffic after protection switching: no
Protected by a fast reroute: none
Downstream repaired: yes
Path recording is desired
SE Style is desired
LSP rerouting is end-to-end-rerouting
OAM MEP entities are not desired
OAM MIP entities are not desired
Downstream information:
Next hop: 172.1.0.2
Signaling interface: Tengigabitethernet0/0/2
Neighbor: 172.1.0.2
Label: 3, type: mpls-label
Incoming ERO Outgoing ERO
---------------------------- ----------------------------
hop0 172.1.0.1/32 172.1.0.2/32
hop1 172.1.0.2/32
Incoming RRO Outgoing RRO
----------------- -----------------
hop0 172.1.0.2 172.1.0.2
hop1 Label 3 Label 3
Tunnel: to_R2, id: 1
LSP name: standby, signaled-name: to_R2@standby, id: 3, Source: 1.1.1.1, Destination: 2.2.2.2
State: up, Status: standby, Protection role: protecting
Direction: ingress, Node protect: disabled, Bandwidth protection requirement: disabled
Carrying the normal traffic after protection switching: no
Protected by a fast reroute: none (protecting)
Downstream repaired: yes
Path recording is desired
SE Style is desired
LSP rerouting is end-to-end-rerouting
OAM MEP entities are not desired
OAM MIP entities are not desired
Downstream information:
Next hop: 172.0.0.2
Signaling interface: Tengigabitethernet0/0/4.3
Neighbor: 172.0.0.2
Label: 19, type: mpls-label
Incoming ERO Outgoing ERO
---------------------------- ----------------------------
hop0 172.0.0.1/32 172.0.0.2/32
hop1 172.0.0.2/32 172.2.0.1/32
hop2 172.2.0.1/32 172.2.0.2/32
hop3 172.2.0.2/32
Incoming RRO Outgoing RRO
----------------- -----------------
hop0 172.0.0.2 172.0.0.2
hop1 Label 19 Label 19
hop2 172.2.0.2 172.2.0.2
hop3 Label 3 Label 3
Так как на пути прохождения R1-R3-R2 выставлена метрика 50, то backup LSP строится по кратчайшему пути через te0/0/4.3.
Добавим, интерфейс te0/0/4.3 в SRLG группу и посмотрим, как изменится путь построения backup LSP:
Построение основного и резервного LSP:
0/ME5100:R1# show mpls rsvp lsps tunnel to_R2
Wed Oct 25 10:40:14 2023
Tunnel: to_R2, id: 1
LSP name: primary, signaled-name: to_R2@primary, id: 1, Source: 1.1.1.1, Destination: 2.2.2.2
State: up, Status: active, Protection role: working
Direction: ingress, Node protect: disabled, Bandwidth protection requirement: disabled
Carrying the normal traffic after protection switching: no
Protected by a fast reroute: none
Downstream repaired: yes
Path recording is desired
SE Style is desired
LSP rerouting is end-to-end-rerouting
OAM MEP entities are not desired
OAM MIP entities are not desired
Downstream information:
Next hop: 172.1.0.2
Signaling interface: Tengigabitethernet0/0/2
Neighbor: 172.1.0.2
Label: 3, type: mpls-label
Incoming ERO Outgoing ERO
---------------------------- ----------------------------
hop0 172.1.0.1/32 172.1.0.2/32
hop1 172.1.0.2/32
Incoming RRO Outgoing RRO
----------------- -----------------
hop0 172.1.0.2 172.1.0.2
hop1 Label 3 Label 3
Tunnel: to_R2, id: 1
LSP name: standby, signaled-name: to_R2@standby, id: 3, Source: 1.1.1.1, Destination: 2.2.2.2
State: up, Status: standby, Protection role: protecting
Direction: ingress, Node protect: disabled, Bandwidth protection requirement: disabled
Carrying the normal traffic after protection switching: no
Protected by a fast reroute: none (protecting)
Downstream repaired: yes
Path recording is desired
SE Style is desired
LSP rerouting is end-to-end-rerouting
OAM MEP entities are not desired
OAM MIP entities are not desired
Downstream information:
Next hop: 172.4.0.2
Signaling interface: Tengigabitethernet0/0/3
Neighbor: 172.4.0.2
Label: 16, type: mpls-label
Incoming ERO Outgoing ERO
---------------------------- ----------------------------
hop0 172.4.0.1/32 172.4.0.2/32
hop1 172.4.0.2/32 172.5.0.1/32
hop2 172.5.0.1/32 172.5.0.2/32
hop3 172.5.0.2/32
Incoming RRO Outgoing RRO
----------------- -----------------
hop0 172.4.0.2 172.4.0.2
hop1 Label 16 Label 16
hop2 172.5.0.2 172.5.0.2
hop3 Label 3 Label 3
Backup LSP построился единственно возможным образом, чтобы избежать построение обоих LSP через линки с одной группой риска.
Далее добавим в SRLG группу интерфейс te0/0/3 на R2:
Построение основного и резервного LSP:
0/ME5100:R2# show running-config mpls rsvp
Wed Oct 25 10:41:05 2023
mpls
rsvp
interface tengigabitethernet 0/0/1
exit
interface tengigabitethernet 0/0/3
srlg DWDM
exit
interface tengigabitethernet 0/0/4
exit
srlg DWDM
group-id 100
exit
Построение основного и резервного LSP:
0/ME5100:R1# show mpls rsvp lsps tunnel to_R2
Wed Oct 25 10:41:33 2023
Tunnel: to_R2, id: 1
LSP name: primary, signaled-name: to_R2@primary, id: 1, Source: 1.1.1.1, Destination: 2.2.2.2
State: up, Protection role: working
Direction: ingress, Node protect: disabled, Bandwidth protection requirement: disabled
Carrying the normal traffic after protection switching: no
Protected by a fast reroute: none
Downstream repaired: yes
Path recording is desired
SE Style is desired
LSP rerouting is end-to-end-rerouting
OAM MEP entities are not desired
OAM MIP entities are not desired
Downstream information:
Next hop: 172.1.0.2
Signaling interface: Tengigabitethernet0/0/2
Neighbor: 172.1.0.2
Label: 3, type: mpls-label
Incoming ERO Outgoing ERO
---------------------------- ----------------------------
hop0 172.1.0.1/32 172.1.0.2/32
hop1 172.1.0.2/32
Incoming RRO Outgoing RRO
----------------- -----------------
hop0 172.1.0.2 172.1.0.2
hop1 Label 3 Label 3
Далее, Backup LSP уже построиться не может т.к работает принцип strict diversity, который запрещает строить primary и backup LSP по одному и тому же пути.