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]

Hi @prathi ,

Good to know that it is still supported in 6.6.3, even though it is through a hidden command.

It is normal that you are seeing no traffic being pushed through the tunnel interface, as no traffic is steered into the tunnel by default. There are various ways you can steer traffic into the TE tunnel. I would recommend using the "autoroute" command under the tunnel interface.

Regards,

[prathi]

Thank you . you are Awesome. 

[Harold Ritter]

You are very welcome @prathi and thanks for the feedback

[prathi]

Hi @Harold Ritter ,

I understood below command that if we send traffic more than 10 kbps in MPLS-TE(RSVP) ,traffic will get switchover to other link if we have more than link for the destination.

RP/0/RP0/CPU0:cisco_ios_XR_7.11.2(config)#rsvp interface gigabitEthernet 0/0/0/1 bandwidth 10
RP/0/RP0/CPU0:cisco_ios_XR_7.11.2(config)#commit
Mon Feb 17 22:25:25.656 IST
Do we have similar command in SR-TE ?  Below configuration serve same purpose as rsvp bandwidth ?

RP/0/RP0/CPU0:xrv9k1#show running-config segment-routing
Mon Feb 17 22:24:20.087 UTC
segment-routing
traffic-eng
policy test
bandwidth 10

[Harold Ritter]

Hi @prathi ,

"rsvp interface gigabitEthernet 0/0/0/1 bandwidth 10" sets the RSVP reservable BW on a given interface.

Whereas "segment-routing traffic-eng policy test bandwidth 10" set the required bandwidth for a given policy.

By the way, bandwidth reservation in the context of SRTE is really different than RSVP. It requires additional element (PCE, CNC, etc).

https://www.cisco.com/c/en/us/td/docs/cloud-systems-management/crosswork-optimization-engine/5-0/UG/b_cisco-crosswork-coe-5_0/m2-bandwidth-on-demand-for-bandwidth-reservation.pdfhttps://www.cisco.com/c/en/us/td/docs/cloud-systems-management/crosswork...

Regards,

[mailatgk]

Hi @Harold Ritter , thank you . I have posted newly in SR-TE conversation . 

[prathi]

HI@Harold Ritter     I have small query  with different between SRTE based on Tunnel and SR-Policy . What is the benefit with SR-policy over  SR-TE based on tunnel ?

[Harold Ritter]

Hi @prathi ,

The SR policies is the new way to configure SRTE. It is more flexible and allows to configure one policy for many destinations, for example. This would be done by configuring a feature called "On Demand Next hop" (ODN).

https://www.segment-routing.net/demos/2016-demo-on-demand-next-hop-large-scale-design/

Regards,

[prathi]

Hi @Harold Ritter  ,  Sorry i have one more question .

I am using SR TE with PCE as mentioned below.  How do i check PCE initiated LSP is being used ?  if not, how to force traffic to use PCE initiated LSP ?

RP/0/RSP0/CPU0:ASR9010YYYYY#show running-config segment-routing
Tue Oct 3 13:45:22.161 GMT
segment-routing
traffic-eng
policy YYYY1322481
source-address ipv4 100.100.93.249
color 10 end-point ipv4 100.100.93.248
autoroute
include all
!
candidate-paths
preference 100
dynamic
pcep
!
metric
type te
!
!
!
!
!
policy XXX12344
source-address ipv4 100.100.93.249
color 1 end-point ipv4 100.100.93.247
autoroute
include all
!
candidate-paths
preference 10
dynamic
pcep
!
metric
type igp
!
!
!
!
!
pcc
source-address ipv4 100.100.93.249
pce address ipv4 100.100.126.253
!
report-all
!
!
!

[Harold Ritter]

Hi @prathi ,

"sh segment-routing traffic-eng forwarding policy" shows you if traffic is forwarded through the policy. You can use a static route or BGP On Demand Next hop to push traffic through the policy.

BGP On Demand Next hop (BGP ODN):

https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/217744-deploy-bgp-soft-next-hop-in-cisco-ios-xr.html

Regards,

[Harold Ritter]

Hi @mailatgk ,

6.6.3 should be ok, but you need to change the sr-policy name configured on the static route as follow:

router static
address-family ipv4 unicast
80.80.80.1/32 sr-policy srte_c_10_ep_92.168.96.24 (name you get in sh seg tra pol)

This should fix the issue.

Regards,

[mailatgk]

Hi Harold,

Thank you very much . Its working.

[Harold Ritter]

You are very welcome @mailatgk and thanks for the feedback

[connectgk28]

Hi @Harold Ritter ,

Thank you . I see you are giving solution to many issues.   I too have one query  ,Could you please help me   ?

What is the MIB i can use to collect info about SR-TE like stats on SR tunnel via SNMP  ?

Regards

Ram

[Harold Ritter]

Hi @connectgk28 ,

You can use the IF-MIB against the SR policy:

cisco@ubuntu:~$ snmpwalk -v 2c -c cisco -L n 192.168.1.1 1.3.6.1.2.1.2.2.1 | grep ".7 ="
IF-MIB::ifIndex.7 = INTEGER: 7
IF-MIB::ifDescr.7 = STRING: srte_c_100_ep_192.168.100.1
IF-MIB::ifType.7 = INTEGER: mplsTunnel(150)
IF-MIB::ifMtu.7 = INTEGER: 1500
IF-MIB::ifSpeed.7 = Gauge32: 0
IF-MIB::ifPhysAddress.7 = STRING:
IF-MIB::ifAdminStatus.7 = INTEGER: up(1)
IF-MIB::ifOperStatus.7 = INTEGER: up(1)
IF-MIB::ifLastChange.7 = Timeticks: (0) 0:00:00.00
IF-MIB::ifInOctets.7 = Counter32: 0
IF-MIB::ifInUcastPkts.7 = Counter32: 0
IF-MIB::ifInDiscards.7 = Counter32: 0
IF-MIB::ifInErrors.7 = Counter32: 0
IF-MIB::ifOutOctets.7 = Counter32: 6576960
IF-MIB::ifOutUcastPkts.7 = Counter32: 63240
IF-MIB::ifOutDiscards.7 = Counter32: 0
IF-MIB::ifOutErrors.7 = Counter32: 0

Regards,