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PCE between IGP domains failing

I can't seem to get an SR policy working between IGP domains using a PCE controller to guide the traffic. 

My topology is as follows (full configs attached):

stevencrutchley_0-1715520661017.png

R1, R2 and PCE are in one ISIS domain. ISIS level-2 point-to-point is running and exchanging loopbacks.
R2, R3 and R4 are in another ISIS domain. ISIS level-2 point-to-point is running and exchanging loopbacks.
R1's loopback is redistributed into ISIS RIGHT.
R4's loopback is redistributed into ISIS LEFT.
R1 and R4 can reach each others loopbacks.
SR is configured everywhere. The SID index is the router number.
A PCEP session is running between R1 and PCE. 
R2 is using `distribute link-state` - with a separate instance ID for both ISIS instances.
R2 has an iBGP session to PCE with the `link-state link-state` address-family.

 

I know that technically both ISIS instances don't need to be in different areas given that they are different IGP domains. This has been done to make it easier to visualise.


R2 has two policies configured. It is delegating path calculation to the PCE for both. 
One policy has an endpoint of R2 (intra domain)
One policy has an endpoint of R4 (inter domain)

The intra domain policy to R2 works. The inter domain one to R4 does not. 

 

 

 

RP/0/RP0/CPU0:PCE#show pce lsp detail 
Sun May 12 13:59:45.491 UTC

PCE's tunnel database: 
----------------------
PCC 10.1.1.1: 

Tunnel Name: cfg_TO-R2_discr_100
Color: 100
Interface Name: srte_c_100_ep_10.1.1.2
 LSPs:
  LSP[0]:
   source 10.1.1.1, destination 10.1.1.2, tunnel ID 2, LSP ID 5
   State: Admin up, Operation active
   Setup type: Segment Routing
   Binding SID: 24006
   Maximum SID Depth: 10
   Preference: 100
   Bandwidth: requested 0 kbps, applied 0 kbps
   Protection type: protected-preferred
   Prefix-SID algorithm: 0 (set: 0)
   PCEP information: 
     PLSP-ID 0x2, flags: D:1 S:0 R:0 A:1 O:2 C:0
   LSP Role: Single LSP
   State-sync PCE: None
   PCC: 10.1.1.1
   LSP is subdelegated to: None
   Reported path: 
     Metric type: IGP, Accumulated Metric 10
      SID[0]: Node, Label 16002, Address 10.1.1.2
   Computed path: (Local PCE) 
     Computed Time: Sun May 12 13:54:52 UTC 2024 (00:04:53 ago)
     Metric type: IGP, Accumulated Metric 10
      SID[0]: Node, Label 16002, Address 10.1.1.2
   Reverse path: (Local PCE) 
     None
     Computed Time: Sun May 12 13:54:52 UTC 2024 (00:04:53 ago)
   Recorded path: 
     None
   Disjoint Group Information: 
     None
   SR Policy Association Group:
     Color: 100, Endpoint: 10.1.1.2
     Policy Name: srte_c_100_ep_10.1.1.2
     Preference: 100

Tunnel Name: cfg_TO-R4_discr_100
Color: 100
Interface Name: srte_c_100_ep_10.1.1.4
 LSPs:
  LSP[0]:
   source 10.1.1.1, destination 10.1.1.4, tunnel ID 1, LSP ID 0
   State: Admin up, Operation down
   Binding SID: None
   Maximum SID Depth: 10
   Preference: 100
   Bandwidth: requested 0 kbps, applied 0 kbps
   Protection type: protected-preferred
   Prefix-SID algorithm: 0 (set: 0)
   PCEP information: 
     PLSP-ID 0x1, flags: D:1 S:0 R:0 A:1 O:0 C:0
   LSP Role: Single LSP
   State-sync PCE: None
   PCC: 10.1.1.1
   LSP is subdelegated to: None
   Reported path: 
     None
   Computed path: (Local PCE) 
     None
     Computed Time: Sun May 12 13:54:52 UTC 2024 (00:04:53 ago)
   Recorded path: 
     None
   Disjoint Group Information: 
     None
   SR Policy Association Group:
     Color: 100, Endpoint: 10.1.1.4
     Policy Name: srte_c_100_ep_10.1.1.4
     Preference: 100

RP/0/RP0/CPU0:PCE#

 

 

 

You can see  the tunnel with 10.1.1.4 end-point is down (from R1 to R4 - interdomain)
But 10.1.1.2 endpoint is fine (intradomain)

Does anyone have any idea what I might be missing? I know the PCE has see the full topology so for some reason it is not calculating it.

1 Accepted Solution

Accepted Solutions

Harold Ritter
Cisco Employee
Cisco Employee

Hi @steven.crutchley ,

You need to configure the router-id for SRTE. Please add the following commands:

R1:

router isis LEFT address-family ipv4 unicast router-id Loopback0

R2:

router isis LEFT address-family ipv4 unicast router-id Loopback0
router isis RIGHT address-family ipv4 unicast router-id Loopback0

R3:

router isis RIGHT address-family ipv4 unicast router-id Loopback0

R4:

router isis RIGHT address-family ipv4 unicast router-id Loopback0

It should fix it.

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

View solution in original post

3 Replies 3

Harold Ritter
Cisco Employee
Cisco Employee

Hi @steven.crutchley ,

You need to configure the router-id for SRTE. Please add the following commands:

R1:

router isis LEFT address-family ipv4 unicast router-id Loopback0

R2:

router isis LEFT address-family ipv4 unicast router-id Loopback0
router isis RIGHT address-family ipv4 unicast router-id Loopback0

R3:

router isis RIGHT address-family ipv4 unicast router-id Loopback0

R4:

router isis RIGHT address-family ipv4 unicast router-id Loopback0

It should fix it.

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

This worked perfectly. Thanks so much.

You are very welcome @steven.crutchley and thanks for the feedback

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México