Segment routing dynamic option

[sachin30720041]

Hello Everyone,

I am new to segment routing. I am trying to learn the dynamic option of segment routing traffic engineering. I have 2 directly connected routers.

R1---R2

R1's Gi0/0/0/1 IP address 100.10.20.1

R2'2 Gi0/0/0/1 IP address 100.10.20.2

1.1.1.1 is the loopback on r1.

2.2.2.2 is the loopback on r2.

Following is the configuration on R1. 

segment-routing

 traffic-eng

  !

  policy pc1

   color 10 end-point ipv4 2.2.2.2

   candidate-paths

    preference 100

     dynamic

      metric

       type igp

router isis 1

 net 49.0001.1111.1111.1111.00

 distribute link-state

 address-family ipv4 unicast

  metric-style wide

  mpls traffic-eng level-1-2

  mpls traffic-eng router-id Loopback0

  segment-routing mpls

 !

 interface Loopback0

  address-family ipv4 unicast

   prefix-sid index 1

  !

 !

 interface GigabitEthernet0/0/0/0

  address-family ipv4 unicast

  !

 !

 interface GigabitEthernet0/0/0/1

  address-family ipv4 unicast

mpls traffic-eng

 interface GigabitEthernet0/0/0/0

 !

Following is the config on R2.

router isis 1

 net 49.0001.2222.2222.2222.00

 distribute link-state

 address-family ipv4 unicast

  metric-style wide

  mpls traffic-eng level-1-2

  mpls traffic-eng router-id Loopback0

  segment-routing mpls

 !

 interface Loopback0

  address-family ipv4 unicast

   prefix-sid index 2

  !

 !

 interface GigabitEthernet0/0/0/0

  address-family ipv4 unicast

  !

 !

 interface GigabitEthernet0/0/0/1

  address-family ipv4 unicast

mpls traffic-eng

 interface GigabitEthernet0/0/0/0

But following command's output shows the invalid path to 2.2.2.2.

While 2.2.2.2 is pingable from 1.1.1.1.

r1#show segment-routing traffic-eng policy    

Fri Sep 10 07:11:23.710 UTC

SR-TE policy database

---------------------

Color: 10, End-point: 2.2.2.2

  Name: srte_c_10_ep_2.2.2.2

  Status:

    Admin: up  Operational: down for 00:38:41 (since Sep 10 06:32:43.463)

  Candidate-paths:

    Preference: 100 (configuration)

      Name: pc1

      Requested BSID: dynamic

      Dynamic (invalid)

      Last error: No path found

srte interface is also down.

RP/0/RP0/CPU0:r1#show ip int br

Fri Sep 10 07:13:58.051 UTC

Interface                      IP-Address      Status          Protocol Vrf-Name

srte_c_10_ep_2.2.2.2           1.1.1.1         Down            Down     default 

I am not sure what configuration am I missing?

Thanks,

Sachin

[Harold Ritter · Accepted solution]

Hi @sachin30720041 ,

Configure your interfaces as point to point under ISIS.

Regards,

[sachin30720041]

Hi Harold,

Thanks for the reply and it worked also.

I have one more question.

In the case of the explicit path, I do not need to give interface type as a point to point. And the

srte_c_10_ep_2.2.2.2 still comes up.

Following is the segment routing config in case of the explicit path.

segment-routing

 traffic-eng

  segment-list seg1

   index 10 address ipv4 2.2.2.2

  !

  policy pc1

   color 10 end-point ipv4 2.2.2.2

   candidate-paths

    preference 100

     explicit segment-list seg1

Why do we need to configure interface type as a point-to-point in case of dynamic option and there is no such need in case of explicit option?

Thanks,

Sachin

[Harold Ritter]

Broadcast interfaces are not supported for SRTE. The fact that it is working for explicit path should not be taken as a reason not to configure the interfaces as p2p.

Regards,

[mailatgk]

Hi Harold, 

We are seeing below issue when we tried to form SR-TE between 2 XRV router. Could you please advise am i missing anything here ?

show segment-routing traffic-eng policy
Mon Aug 28 06:34:27.775 UTC

SR-TE policy database
---------------------

Color: 10, End-point: 92.168.96.24
Name: srte_c_10_ep_92.168.96.24
Status:
Admin: up Operational: down for 4w3d (since Jul 27 11:37:54.474)
Candidate-paths:
Preference: 100 (configuration)
Name: Nokia
Requested BSID: dynamic
Dynamic (invalid)
Last error: No path found
Metric Type: IGP, Path Accumulated Metric: 0
Attributes:
Forward Class: 0
Steering BGP disabled: no
IPv6 caps enable: no

XRV B:

Mon Aug 28 06:14:50.531 UTC
segment-routing
traffic-eng
interface GigabitEthernet0/0/0/2.10
metric 100
!
policy Nokia
color 100 end-point ipv4 92.168.96.26
candidate-paths
preference 100
dynamic
metric
type igp
!
!
!
!
!
!
!

router ospf 1
router-id 92.168.96.24
redistribute connected
address-family ipv4 unicast
area 0.0.0.0
mpls traffic-eng
segment-routing mpls
interface Loopback0
passive enable
prefix-sid index 1001
!
interface GigabitEthernet0/0/0/0.10
network point-to-point
!
interface GigabitEthernet0/0/0/1.10
network point-to-point
!
interface GigabitEthernet0/0/0/2.10
network point-to-point
!
!
mpls traffic-eng router-id Loopback0
!

RP/0/RP0/CPU0:_XRv-B#show ospf neighbor
Mon Aug 28 06:37:24.750 UTC

* Indicates MADJ interface
# Indicates Neighbor awaiting BFD session up

Neighbors for OSPF 1

Neighbor ID Pri State Dead Time Address Interface
92.168.96.69 1 FULL/ - 00:00:36 10.10.11.1 GigabitEthernet0/0/0/0.10
Neighbor is up for 1w0d
92.168.96.26 1 FULL/ - 00:00:35 10.10.15.1 GigabitEthernet0/0/0/2.10
Neighbor is up for 1w0d

XRVA :

RP/0/RP0/CPU0:XRv-A#show running-config segment-routing
Mon Aug 28 06:12:44.575 UTC
segment-routing
traffic-eng
interface GigabitEthernet0/0/0/2.10
metric 100
!
policy Nokia
color 10 end-point ipv4 92.168.96.24
candidate-paths
preference 100
dynamic
metric
type igp
!
!
!
!
!
!
!

RP/0/RP0/CPU0:XRv-A#show running-config router ospf
Mon Aug 28 06:33:54.667 UTC
router ospf 0
area 0.0.0.0
!
!
router ospf 1
router-id 92.168.96.26
redistribute connected
area 0.0.0.0
segment-routing mpls
interface Loopback0
prefix-sid index 1001
!
interface GigabitEthernet0/0/0/0.10
network point-to-point
!
interface GigabitEthernet0/0/0/1.10
network point-to-point
!
interface GigabitEthernet0/0/0/2.10
network point-to-point
!
!
mpls traffic-eng router-id Loopback0
!

RP/0/RP0/CPU0:XRv-A#show ospf neighbor
Mon Aug 28 06:36:46.357 UTC

* Indicates MADJ interface
# Indicates Neighbor awaiting BFD session up

Neighbors for OSPF 1

92.168.96.24 1 FULL/ - 00:00:35 10.10.15.2 GigabitEthernet0/0/0/2.10
Neighbor is up for 1w0d

[Harold Ritter]

Hi @mailatgk ,

Quickly reviewing the configuration you provided, I can see two things that need to be changed.

1. You are using the same prefix SID on both routers (prefix-sid index 1001). The prefix SID needs to be unique.

2. You need to add the following command under ospf, so that the ospf topology is available to SRTE.

 distribute link-state

Regards, 

[mailatgk]

Hi Harold,

Thank you very much . Its working . You are genius.

[Harold Ritter]

You are very welcome @mailatgk and thanks for the feedback

[mailatgk]

Hi Harold,

Sorry to bother you today as well. I am in learning phase , kindly help me to address below query

Adding to my earlier SR-TE setup config , i am trying to configure static route for XRVB loopback80 address over SR TE  but its not getting added in routing table. Only IGP routes for loopback80 is getting added in routing table. How do i ensure that traffic is going via SR-TE from XRV-A to B ?

XRV-A ----- XRV-B 

RP/0/RP0/CPU0:XRv-A#show running-config router static
Tue Aug 29 16:58:30.539 UTC
router static
address-family ipv4 unicast
80.80.80.1/32 sr-policy Nokia

RP/0/RP0/CPU0:1_XRv-B#show running-config interface Loopback80
Tue Aug 29 17:07:54.482 UTC
interface Loopback80
ipv4 address 80.80.80.1 255.255.255.255
!

RP/0/RP0/CPU0:ramadoss_1_XRv-A#show route 80.80.80.1/32
Tue Aug 29 17:15:20.147 UTC

Routing entry for 80.80.80.1/32
Known via "ospf 1", distance 110, metric 20, type extern 2
Installed Aug 29 06:20:58.893 for 10:54:21
Routing Descriptor Blocks
10.10.15.2, from 92.168.96.24, via GigabitEthernet0/0/0/2.10
Route metric is 20
No advertising protos.

[Harold Ritter]

Hi @mailatgk ,

I suspect it doesn't work for you because of the version you are running in your lab.  You are running XRv not XR9000v, right? What version is it that you are running?

Regards,

[mailatgk]

Hi @Harold Ritter ,

Please find the version . Also please suggest how i can ensure traffic(atleast ping) is flowing via SR-TE with this topology.

XRV-A --- XRV-B.

RP/0/RP0/CPU0:XRv-A#show version
Wed Aug 30 14:47:41.823 UTC
Cisco IOS XR Software, Version 6.6.3
Copyright (c) 2013-2019 by Cisco Systems, Inc.

Build Information:
Built By : hlo
Built On : Fri Dec 13 16:42:11 PST 2019
Built Host : iox-ucs-033
Workspace : /auto/srcarchive15/prod/6.6.3/xrv9k/ws
Version : 6.6.3
Location : /opt/cisco/XR/packages/

cisco IOS-XRv 9000 () processor
System uptime is 8 weeks 5 days 2 hours 27 minutes

[prathi]

Hello @Harold Ritter  ,

I too have setup with SR-policy Traffic engineering  same as @mailatgk   .  Now i want to change it to SR-TE LSP from SR-policy .  What are the configuration i  need to change or add to have working SR-TE LSP in my setup (2 XRV connected back to back running version 6.6.3) . Could you please help here ? as i am beginner in SR, i am struggling  to get SR-TE LSP working in my setup .

[Harold Ritter]

Hi @prathi ,

> Now i want to change it to SR-TE LSP from SR-policy . 

What do you mean by SRTE LSP? Do you mean SRTE LSPs based on tunnel interfaces? Tunnel interfaces can still be used to configure MPLS TE LSPs, but can no longer be used to configure SRTE LSPs in 6.6.3. You need to use SRTE policies instead.

Regards,

[prathi]

Thank you Very much for the info,  yes i meant  SRTE LSPs based on tunnel interfaces .

[prathi]

HI@Harold Ritter ,

Yes i meant SRTE LSPs based on tunnel interfaces . I see segment routing command is hidden under tunnel interface in 6.6.3.

But still i am able to configure the SRTE LSPs based on tunnel interface. I see tunnel is UP .

When i tried to ping with SR-mpls destination Loopback  , Ping is going  but counter is not getting increased in tunnel-interface .  

How do i ensure that packet is going via tunnel interface only ? Why packet count not getting increased in SR-TE in below forwarding table when we ping.

RP/0/RP0/CPU0:1_XRv-A#show mpls forwarding
Tue Sep 5 14:26:57.175 UTC
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
------ ----------- ------------------ ------------ --------------- ------------
16001 Pop SR Pfx (idx 1) Gi0/0/0/2.10 10.10.15.2 1125837
24000 Pop SR Adj (idx 0) Gi0/0/0/2.10 10.10.15.2 0
24001 Pop SR Adj (idx 0) Gi0/0/0/0.10 10.10.12.1 0
24002 Pop SR Adj (idx 0) Gi0/0/0/1.10 10.10.14.1 0
24003 Pop TE: 61442 Gi0/0/0/2.10 10.10.15.2 0
24006 Pop No ID tt7 point2point 0
24007 Pop SR TE: 7 [TE-INT] Gi0/0/0/2.10 10.10.15.2 0 

RP/0/RP0/CPU0:XRv-A#ping sr-mpls 92.168.96.24/32 repeat 100
Tue Sep 5 13:52:52.492 UTC

Sending 100, 100-byte MPLS Echos to 92.168.96.24/32,
timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (100/100), round-trip min/avg/max = 2/4/13 ms

RP/0/RP0/CPU0:XRv-A#show running-config interface tunnel-te 7
Tue Sep 5 13:58:20.641 UTC
interface tunnel-te7
description RSVPtunnel
ipv4 unnumbered Loopback0
destination 92.168.96.24
path-option 1 dynamic segment-routing  
!

RP/0/RP0/CPU0:XRv-A#show mpls traffic-eng tunnels 7
Tue Sep 5 13:50:57.195 UTC

Name: tunnel-te7 Destination: 92.168.96.24 Ifhandle:0x1c
Signalled-Name:XRv-A_t7
Status:
Admin: up Oper: up Path: valid Signalling: connected

path option 1, (Segment-Routing) type dynamic (Basis for Setup, path weight 1)
Accumulative metrics: TE 1 IGP 1 Delay 300000
G-PID: 0x0800 (derived from egress interface properties)
Bandwidth Requested: 0 kbps CT0
Creation Time: Wed Jul 19 16:48:33 2023 (6w5d ago)
Config Parameters:
Bandwidth: 0 kbps (CT0) Priority: 7 7 Affinity: 0x0/0xffff
Metric Type: TE (global)
Path Selection:
Tiebreaker: Min-fill (default)
Protection: any (default)
Hop-limit: disabled
Cost-limit: disabled
Delay-limit: disabled
Path-invalidation timeout: 10000 msec (default), Action: Tear (default)
AutoRoute: disabled LockDown: disabled Policy class: not set
Forward class: 0 (not enabled)
Forwarding-Adjacency: disabled
Autoroute Destinations: 0
Loadshare: 0 equal loadshares
Auto-bw: disabled
Auto-Capacity: Disabled:
Path Protection: Not Enabled
BFD Fast Detection: Disabled
Reoptimization after affinity failure: Enabled
SRLG discovery: Disabled
History:
Tunnel has been up for: 07:57:22 (since Tue Sep 05 05:53:35 UTC 2023)
Current LSP:
Uptime: 07:57:22 (since Tue Sep 05 05:53:35 UTC 2023)
Reopt. LSP:
Last Failure:
LSP not signalled, identical to the [CURRENT] LSP
Date/Time: Tue Sep 05 06:39:23 UTC 2023 [07:11:34 ago]
Prior LSP:
ID: 11 Path Option: 1
Removal Trigger: tunnel shutdown

Segment-Routing Path Info (OSPF 1 area 0.0.0.0)
Segment0[Link]: 10.10.15.1 - 10.10.15.2, Label: 24000