ospf inter-datacenter traffic primario over-backbone and backup over services-provider con verifica redistribuzione prefix ospf IA E1 E2

30.03 2020 | by massimiliano

ARCHITETTURA DI RIFERIMENTO Obiettivo di questo documento è quello di evidenziare il traffico Inter-DataCenter over backbone (simile […]

https://www.ingegnerianetworking.com/wp-content/uploads/2020/03/ospf-interdc-backbone-e95.png

ARCHITETTURA DI RIFERIMENTO

ospf interdc backbone

Obiettivo di questo documento è quello di evidenziare il traffico Inter-DataCenter over backbone (simile al concetto di DCI-L3 west-east path) ed in caso di eventuale fault a livello backbone domain utilizzare in modo dinamico un path di backup over service provider via peering EBGP verso i rispettivi POP

Si riportano le configurazioni di LAB

DATACENTER di SX:

ABR-SX

EGR-SX

interface GigabitEthernet0/1

description to-backbone

no ip address

no cdp enable

interface GigabitEthernet0/1.1008

description to-backbone-ospf8

encapsulation dot1Q 1008

ip address 10.141.8.100 255.255.255.0

ip ospf 1 area 0.0.0.8

no cdp enable

interface GigabitEthernet0/3

description LAN

ip address 10.10.10.1 255.255.255.0

ip ospf 1 area 0.0.0.8

no cdp enable

router ospf 1

interface GigabitEthernet0/0

description to-backbone

no ip address

interface GigabitEthernet0/0.141

description to-backbone-area0

encapsulation dot1Q 141

ip address 10.141.0.10 255.255.255.0

ip ospf 1 area 0.0.0.0

interface GigabitEthernet0/0.1008

description to-backbone-area8

encapsulation dot1Q 1008

ip address 10.141.8.10 255.255.255.0

ip ospf 1 area 0.0.0.8

router ospf 1

ip vrf INTRA

rd 64512:10

interface Loopback0

ip address 3.3.3.3 255.255.255.255

interface Loopback1

ip vrf forwarding INTRA

ip address 33.33.33.33 255.255.255.255

interface GigabitEthernet0/0

description to-SP

ip vrf forwarding INTRA

ip address 192.168.0.2 255.255.255.252

interface GigabitEthernet0/3

description to-backbone

no ip address

interface GigabitEthernet0/3.1008

description to-backbone-ospf8

encapsulation dot1Q 1008

ip vrf forwarding INTRA

ip address 10.141.8.20 255.255.255.0

ip ospf 1 area 0.0.0.8

router ospf 1 vrf INTRA

capability vrf-lite

redistribute bgp 64512 subnets

router bgp 64512

bgp router-id 3.3.3.3

bgp log-neighbor-changes

address-family ipv4 vrf INTRA

bgp router-id 33.33.33.33

redistribute ospf 1

neighbor 192.168.0.1 remote-as 100

neighbor 192.168.0.1 activate

neighbor 192.168.0.1 route-map PREP out

exit-address-family

ip prefix-list PRX-DX seq 5 permit 20.20.20.0/24

ip prefix-list PRX-SX seq 5 permit 10.10.10.0/24

route-map PREP permit 10

match ip address prefix-list PRX-SX

route-map PREP permit 20

match ip address prefix-list PRX-DX

set as-path prepend 64512

DATACENTER di DX:

ABR-DX

EGR-DX

interface Loopback100

ip address 100.100.100.100 255.255.255.255

interface GigabitEthernet0/1

description to-backbone

no ip address

interface GigabitEthernet0/1.1016

description to-bb-ospf16

encapsulation dot1Q 1016

ip address 10.141.16.100 255.255.255.0

ip ospf 1 area 0.0.0.16

interface GigabitEthernet0/3

description LAN

ip address 20.20.20.1 255.255.255.0

ip ospf 1 area 0.0.0.16

router ospf 1

redistribute connected metric-type 1 subnets

interface GigabitEthernet0/0

description to-backbone

no ip address

duplex auto

speed auto

media-type rj45

interface GigabitEthernet0/0.141

description to-BB

encapsulation dot1Q 141

ip address 10.141.0.12 255.255.255.0

ip ospf 1 area 0.0.0.0

interface GigabitEthernet0/0.1016

description ospf-16

encapsulation dot1Q 1016

ip address 10.141.16.10 255.255.255.0

ip ospf 1 area 0.0.0.16

router ospf 1

ip vrf INTRA

rd 64513:10

interface Loopback0

ip address 4.4.4.4 255.255.255.255

interface GigabitEthernet0/0

description to-SP

ip vrf forwarding INTRA

ip address 192.168.0.6 255.255.255.252

no cdp enable

interface GigabitEthernet0/3

description backbone

no ip address

no cdp enable

interface GigabitEthernet0/3.1016

description to-backbone

encapsulation dot1Q 1016

ip vrf forwarding INTRA

ip address 10.141.16.20 255.255.255.0

ip ospf 1 area 0.0.0.16

no cdp enable

router ospf 1 vrf INTRA

capability vrf-lite

redistribute bgp 64513 subnets

router bgp 64513

bgp router-id 4.4.4.4

bgp log-neighbor-changes

address-family ipv4 vrf INTRA

redistribute ospf 1 match internal external 1 external 2

neighbor 192.168.0.5 remote-as 100

neighbor 192.168.0.5 activate

neighbor 192.168.0.5 route-map PREP out

exit-address-family

ip prefix-list PRX-DX seq 5 permit 20.20.20.0/24

ip prefix-list PRX-SX seq 5 permit 10.10.10.0/24

route-map PREP permit 10

match ip address prefix-list PRX-DX

route-map PREP permit 20

match ip address prefix-list PRX-SX

set as-path prepend 64513

route-map PREP permit 30

I router di egress hanno il solo compito di CE e mai hanno una funzione attiva di annunci e/o redistribuzione di prefix come invece hanno gli altri devices presenti nelle rispettive aree ospf di competenza; quindi lato router di egress (CE) la ricezione di prefix appartenenti al datacenter opposto via BGP come best-path è normale e corretta.

E’ importante, invece, che i soli router attivi cioà quelli delegati ad annunciare e redistribuire le prefix ricevano le destinazioni con next-hop il router prima appartenente al backdoor link backbone e come “backup” il next-hop del router egress di pertinenza.

Preferred Path selection OSPF:

Intra-Area (O)
Inter-Area (O IA)
External Type 1 (E1)
NSSA Type 1 (N1)
External Type 2 (E2)
NSSA Type 2 (N2)

Verifica OUTPUT:

R1#show ip route

Codes: L – local, 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, H – NHRP, l – LISP

a – application route

+ – replicated route, % – next hop override, p – overrides from PfR

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks

C 10.10.10.0/24 is directly connected, GigabitEthernet0/3

L 10.10.10.1/32 is directly connected, GigabitEthernet0/3

11.0.0.0/32 is subnetted, 1 subnets

20.0.0.0/24 is subnetted, 1 subnets

O IA 20.20.20.0 [110/4] via 10.141.8.10, 02:50:48, GigabitEthernet0/1.1008 # NH via ABR-SX

O E1 100.100.100.100 [110/23] via 10.141.8.10, 02:19:27, GigabitEthernet0/1.1008 # NH via ABR-SX

La rete 10.10.10.0/24 è direttamente connessa

La rete 20.20.20.0/24 annunciata direttamente da R2 (DC-SX)) è vista via Inter-Area OSPF from ABR-RZ

La rete 100.100.100.100/32 redistribuita da R2 (DC-SX) è vista come External Type 1 OSPF from ABR-RZ

Ovviamente il Router R2 ha la seguente configurazione di redistrione in OSPF:

router ospf 1

redistribute connected metric-type 1 subnets

R1#show ip ospf database

OSPF Router with ID (10.141.8.100) (Process ID 1)

Router Link States (Area 0.0.0.8)

Link ID ADV Router Age Seq# Checksum Link count

10.141.0.10 10.141.0.10 648 0x8000000E 0x0035FE 1

10.141.8.20 10.141.8.20 615 0x80000010 0x008F73 1

10.141.8.100 10.141.8.100 449 0x8000000F 0x00BD28 2

Net Link States (Area 0.0.0.8)

Link ID ADV Router Age Seq# Checksum

10.141.8.100 10.141.8.100 944 0x80000011 0x00AA1A

Summary Net Link States (Area 0.0.0.8)

Link ID ADV Router Age Seq# Checksum

10.141.0.0 10.141.0.10 648 0x8000000D 0x0053A3

10.141.16.0 10.141.0.10 648 0x80000006 0x00BA32

20.20.20.0 10.141.0.10 648 0x80000006 0x00C78F # ADV Router = ABR-SX

Summary ASB Link States (Area 0.0.0.8)

Link ID ADV Router Age Seq# Checksum

10.141.16.20 10.141.0.10 648 0x80000006 0x00E3F3

10.141.16.100 10.141.0.10 1424 0x80000005 0x00C2C5

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag

10.10.10.0 10.141.16.20 1678 0x80000007 0x001FE5 3489725441 # ADV Router = EGR-DX

11.11.11.11 10.141.8.20 1890 0x80000007 0x00B24D 3489725440

11.11.11.11 10.141.16.20 1678 0x80000009 0x00886C 3489725441

20.20.20.0 10.141.16.20 554 0x80000001 0x00C12B 3489725441 # ADV Router = EGR-DX

22.22.22.22 10.141.8.20 1890 0x80000007 0x00B61D 3489725440

22.22.22.22 10.141.16.20 921 0x80000009 0x008C3C 3489725441

100.100.100.100 10.141.8.20 540 0x80000001 0x00B0EF 3489725440 # ADV Router = EGR-SX

100.100.100.100 10.141.16.100 655 0x80000006 0x00BEBF 0 # ADV Router = R2

192.168.0.0 10.141.16.20 1678 0x80000009 0x00C0F9 3489725441

192.168.0.4 10.141.8.20 615 0x80000009 0x00BE01 3489725440

R1#

Il traffico inter-DC primario è rappresentanto in figura:

ospf interdc backbone orizzontale traffic

EGR-SX#show ip route vrf INTRA

Routing Table: INTRA

Codes: L – local, 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, H – NHRP, l – LISP

a – application route

+ – replicated route, % – next hop override, p – overrides from PfR

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks

O 10.10.10.0/24

[110/2] via 10.141.8.100, 03:42:01, GigabitEthernet0/3.1008

20.0.0.0/24 is subnetted, 1 subnets

B 20.20.20.0 [20/0] via 192.168.0.1, 00:20:43

22.0.0.0/32 is subnetted, 1 subnets

100.0.0.0/32 is subnetted, 1 subnets

B 100.100.100.100 [20/0] via 192.168.0.1, 00:45:49

EGR-SX#

In caso di FAULT from DataCenter di SX

Nel Test spegniamo il router ABR-DX:

R1#show ip route

Codes: L – local, 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, H – NHRP, l – LISP

a – application route

+ – replicated route, % – next hop override, p – overrides from PfR

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks

C 10.10.10.0/24 is directly connected, GigabitEthernet0/3

L 10.10.10.1/32 is directly connected, GigabitEthernet0/3

O E2 20.20.20.0 [110/1] via 10.141.8.20, 00:00:23, GigabitEthernet0/1.1008 # NH via EGR-SX

O E2 100.100.100.100 [110/1] via 10.141.8.20, 00:00:23, GigabitEthernet0/1.1008 # NH via EGR-SX

R1#show ip ospf database external 100.100.100.100

OSPF Router with ID (10.141.8.100) (Process ID 1)

Type-5 AS External Link States

LS age: 425

Options: (No TOS-capability, DC, Upward)

LS Type: AS External Link

Link State ID: 100.100.100.100 (External Network Number )

Advertising Router: 10.141.8.20 # ADV Router = EGR-SX

LS Seq Number: 80000002

Checksum: 0xAEF0

Length: 36

Network Mask: /32

Metric Type: 2 (Larger than any link state path)

MTID: 0

Metric: 1

Forward Address: 0.0.0.0

External Route Tag: 3489725440

LS age: 2470

Options: (No TOS-capability, DC, Upward)

LS Type: AS External Link

Link State ID: 100.100.100.100 (External Network Number )

Advertising Router: 10.141.16.100 # ADV Router = R2

LS Seq Number: 80000006

Checksum: 0xBEBF

Length: 36

Network Mask: /32

Metric Type: 1 (Comparable directly to link state metric)

MTID: 0

Metric: 20

Forward Address: 0.0.0.0

External Route Tag: 0

R1#

Il traffico inter-DC di backup è rappresentanto in figura:

ospf interdc backbone verticale traffic

Questo semplice esempio ci fa ricordare un’altro tipo di architettura DataCenter multisite:

DC ACI mbbgp ospf dcil3

Dove R1 ed R2 sono i nostri Leaf mentre i router di Egress sono i nostri Spine