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IOS-XR MPLS TE Auto Tunnel Backup Bandwidth Protection

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yosef_manasseh
Cisco Employee

IOS-XR MPLS TE Auto Tunnel Backup Bandwidth Protection

 

Current Implementation of MPLS TE Auto Tunnel Backup

 

In an MPLS-TE network, LSPs can be protected by FRR link protection (a.k.a. "NHop protection") or node protection (a.k.a. "NNHop protection").
This is achieved by creating backup LSP protecting links or nodes that the LSP passes.


The node which redirects the traffic onto the backup LSP is called the Point of Local Repair (PLR), and PLR can be the primary LSP head-end itself, or transit router along the path.

 

Figure 1: FRR link protection

 

fig1.png

 

 

 

 

 

 

 

Figure 2: FRR node protection

 

fig2.png

 

 

 

 

 

 

 

 

 

 

When the protected link or node goes down, traffic will switch from the primary LSP to the backup LSP, resulting in a very minimal traffic loss.
Traffic will be forwarded using this backup LSP until the primary LSP can be signaled again using the original path.
When the original path becomes available again, traffic will switch back to primary LSP without any packet loss.

In some cases, a particular primary LSP can be protected by both link protection and node protection.
The current implementation of IOS XR FRR is that node protection is preferred to link protection, meaning when a particular primary LSP can be protected by either node protection or link protection, IOS XR will select node protection for use. When this selection happens, link protection LSP will not be used and will eventually be aged out and removed.

Figure 3: node protection is preferred to link protection

 

fig3.png

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Backup LSP can either be statically created by operator or automatically created by the router.
Both static and auto backup are existing IOS XR functionalities.

 

When the backup LSP is configured to be automatically created, IOS XR will auto create:
1. One backup LSP for link protection per protected link.
2. One backup LSP for node-protection per protected node.

 

As it's currently implemented in IOS XR, these auto-tunnels will be signalled with zero RSVP bandwidth.


Potential issue with current implementation of MPLS TE auto tunnel backup

 

When a link/node down event is taking place, it is possible that many primary LSPs will all fall back to a same backup LSP. When this many primary LSPs are each carrying a significant amount of traffic, this will potentially cause a traffic bottleneck on the back up physical link, affecting many other unrelated traffic streams using that link.

Figure 4: FRR causes a traffic bottleneck on the back up physical link

 

fig4.png

 

 

 

 

 

 

 

 

 

 

 

 

 

There is a need to control how much bandwidth can be protected by a particular auto backup LSP in the control plane. If such control exists, then a link/node down event will less likely to saturate a backup link since only certain amount of bandwidth will be consumed by the backup LSP on that link.
Let's refer to this particular need as need #1 "a need to control how much bandwidth can be protected".

Now let's take one step further. Even if such control exists, the auto backup LSP is signalled with 0 RSVP bandwidth. Meaning the auto backup LSP will always be successfully signalled over a particular physical link even if that link's RSVP bandwidth has been heavily used already (say by other unrelated LSPs using that link).
When a link/node down event is taking place, we will still be facing an issue where a traffic bottleneck might occur on the back up physical link.
There is a need for an auto backup LSP to signal a specific bandwidth value instead of just 0 value.
Let's refer to this particular need as need #2 "a need for an auto backup LSP to signal a specific bandwidth".

Finally, when an auto backup LSP becomes capable of signalling a specific bandwidth, then there will now be a need for a network operator to soft-preempt these backups in case the bandwidth they are reserving is needed by a higher priority LSP. Soft-preemption will allow the backups to keep on carrying traffic while the control plane is trying to find other path to create a new backup, instead of the control plane bringing down (hard-preempt) the backups right away.
Let's refer to this particular need as need #3 "a need to soft-preempt auto backups".

Figure 5: auto backup LSPs being soft pre-empted

 

fig5.png


 

 

 

 

 

 

 

 

 

 

 

Enhancement to MPLS TE auto backup in IOS XR 7.5.1

 

Disclaimer:
7.5.1 might not be a GA (general availablity) release.

Starting with IOS XR 7.5.1, with regards to auto backup LSPs, the following model is introduced:

 

  1. Create 1 link-protection auto-tunnel backup per protected-link providing bandwidth protection.
  2. Create 1 node-protection auto-tunnel backup per protected-node providing bandwidth-protection.
  3. Use the bandwidth protection backups only to protect LSPs that are requesting bandwidth-protection.
  4. Limit the amount of protected bandwidth per backup tunnel through configuration.
    This is addressing need #1 "a need to control how much bandwidth can be protected" described in the previous section.
  5. If there is no more room to protect LSPs requesting bandwidth protection, then use the regular auto-tunnel backups to provide FRR protection.
  6. Support signalled-bandwidth configuration under the attribute sets for auto-tunnel backups.
    This is addressing need #2 "a need for an auto backup LSP to signal a specific bandwidth" described in the previous section.
  7. Signal the auto-tunnel backups with ZERO bandwidth in case no path is found with the configured bandwidth.
    If this happens, keep trying to reoptimize to satisfy the bandwidth requirement.
  8. Support soft-preemption configuration in the auto-tunnel backup attribute set.
    This is addressing need #3 "a need to soft-preempt auto backups" described in the previous section.

 

Note that as a result of the new feature:

 

  • In case of a link needing protection,
    Two link protection auto backup LSPs will be brought up:
    one to provide link-protection with bandwidth protection, and one to provide link-protection without bandwidth protection.
  • Likewise, in case of a node needing protection,
    Two node protection auto backup LSPs will be brought up:
    one to provide node-protection with bandwidth protection, and one to provide node-protection without bandwidth protection.


Three new CLI configuration is introduced as part of this feature:

  • Limit the amount of protected bandwidth per backup tunnel.
  • Signalled-bandwidth configuration under the attribute sets for auto-tunnel backups.
  • Soft-preemption configuration in the auto-tunnel backup attribute set.


Please refer to section "Config Summary" for sample CLI configuration.

Users can pick and choose which configuration they want to use.
I.e. there is no requirement to have all three new CLI configuration active at the same time.
For instance, users can limit the amount of protected bandwidth per backup tunnel without having the backup tunnel to signal any specific bandwidth value.
Or maybe a user configures protected bandwidth limit with bandwidth signaling, but without configuring soft-preemption.

Please refer to "Config Example" section for more CLI config details along with relevant show command output.

 


Supported Hardware

"MPLS TE auto backup Bandwidth Protection" is an IOS-XR platform independent feature.
As such you can configure this feature on IOS-XR platforms such as ASR9000, NCS5500, and so on, as long as it runs IOS XR 7.5.1 or above.

 

Config Example

 

Acronyms and definitions for terms used throughout this section:

  • NHOP+BW : Link protection backup auto tunnel that is bandwidth protected
  • NHOP-BW : Link protection backup auto tunnel that is NOT bandwidth protected
  • NNHOP+BW : Node protection backup auto tunnel that is bandwidth protected
  • NNHOP-BW : Node protection backup auto tunnel that is NOT bandwidth protected
  • PT+BW : Primary tunnel that is requesting for FRR bandwidth protection
  • PT-BW : Primary tunnel that is NOT requesting for FRR bandwidth protection

"Tunnel" and "LSP" refers to same thing and are being used interchangeably.

 

Topology


Figure 6
fig6.png

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Base configuration

IGP is ISIS, RSVP and mpls traffic-eng are configured in all relevant interfaces.
We have two primary LSPs:
- tunnel-te1 which is a PT+BW.
- tunnel-te2 which is a PT-BW.

LSP head end is on R1, tail end is on R2.
Both LSPs are using path S1-S2-S3.

Relevant config on R1-ichitaka:

 

ipv4 unnumbered mpls traffic-eng Loopback0

router isis main
net 47.0005.1111.1111.1111.00
nsr
distribute link-state
log adjacency changes
address-family ipv4 unicast
metric-style wide
mpls traffic-eng level-1-2
mpls traffic-eng router-id Loopback0
router-id Loopback0
!
address-family ipv6 unicast
metric-style wide
router-id Loopback0
!
interface Loopback0
passive
address-family ipv4 unicast
!
address-family ipv6 unicast
!
!
interface HundredGigE0/1/0/0.1
point-to-point
address-family ipv4 unicast
!
address-family ipv6 unicast
!
!
interface HundredGigE0/1/0/0.2
point-to-point
address-family ipv4 unicast
!
address-family ipv6 unicast
!
!
!

rsvp
interface HundredGigE0/1/0/0.1
bandwidth 10000000
!
interface HundredGigE0/1/0/0.2
bandwidth 10000000
!
!

mpls traffic-eng
interface HundredGigE0/1/0/0.1
!
interface HundredGigE0/1/0/0.2
!
logging events all
reoptimize 604800
!

explicit-path name R1_vlan1_R9_R6_R2
index 1 next-address strict ipv4 unicast 100.1.0.9
index 2 next-address strict ipv4 unicast 100.5.0.6
index 3 next-address strict ipv4 unicast 100.4.0.2
!

interface tunnel-te1
ipv4 unnumbered Loopback0
ipv6 enable
signalled-bandwidth 1000000
destination 200.1.1.2
fast-reroute protect bandwidth
path-option 10 explicit name R1_vlan1_R9_R6_R2
!

interface tunnel-te2
ipv4 unnumbered Loopback0
ipv6 enable
signalled-bandwidth 1000000
destination 200.1.1.2
fast-reroute
path-option 10 explicit name R1_vlan1_R9_R6_R2
!

 


All primary LSPs are up:

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels tabular

Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te1 2 200.1.1.2 200.1.1.1 up Inact Head Inact
tunnel-te2 2 200.1.1.2 200.1.1.1 up Inact Head Inact

 

 

Each primary LSP is consuming 1G of RSVP bandwidth along the path:

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh rsvp interface

*: RDM: Default I/F B/W % : 75% [default] (max resv/bc0), 0% [default] (bc1)

Interface MaxBW (bps) MaxFlow (bps) Allocated (bps) MaxSub (bps)
------------------------- ------------ ------------- -------------------- -------------
HundredGigE0/1/0/0.1 10G 10G 2G ( 20%) 0
HundredGigE0/1/0/0.2 10G 10G 0 ( 0%) 0



Note that both primary LSPs are using same segment HundredGigE0/1/0/0.1 (S1 in figure 7).
We will create link protection over this sub-interface later.

Now let's create the auto backup with no bandwidth protection, which is an existing feature.
Let's do link protection for segment S1.

 

mpls traffic-eng
 interface HundredGigE0/1/0/0.1
 auto-tunnel backup
 !
!



NHOP-BW tunnel-te65005 becomes active.

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels tabular

Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te1 2 200.1.1.2 200.1.1.1 up Ready Head Inact
tunnel-te2 2 200.1.1.2 200.1.1.1 up Ready Head Inact
*tunnel-te65005 2 200.1.1.9 200.1.1.1 up Inact Head Inact
* = automatically created backup tunnel



Tunnel-te65005 head end is R1, and tail-end is R9. It's protecting segment S1 by taking backup path S4.
Moreover, it is signalled with 0 bandwidth, as per existing feature.

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels 65005

Name: tunnel-te65005 Destination: 200.1.1.9 Ifhandle:0x20ab0a0 (auto-tunnel backup)
Signalled-Name: autob_R1-Ichitaka-ASR9904_t65001_Hu0_1_0_0.1
Status:
Admin: up Oper: up Path: valid Signalling: connected

path option (autob_nhop_te65005), preference 20, type explicit (autob_nhop_te65005) (Basis for Setup, path weight 10)
Accumulative metrics: TE 10 IGP 10 Delay 300000
path option (autob_nhop_srlg_te65005), preference 10, type explicit (autob_nhop_srlg_te65005) [disabled]
G-PID: 0x0800 (derived from egress interface properties)
Bandwidth Requested: 0 kbps CT0 <--- signalled with 0 bandwidth
Creation Time: Thu Jul 1 11:08:13 2021 (00:14:38 ago)
Config Parameters:
Bandwidth: 0 kbps (CT0) Priority: 7 7 Affinity: 0x0/0xffff
Metric Type: TE (global)
Path Selection:
Tiebreaker: Min-fill (default)
Hop-limit: disabled
Cost-limit: disabled
Delay-limit: disabled
Delay-measurement: 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:
Fast Reroute: Disabled, Protection Desired: None
Path Protection: Not Enabled
BFD Fast Detection: Disabled
Reoptimization after affinity failure: Enabled
Soft Preemption: Disabled
Auto Backup:
Protected LSPs: 2 <--- protecting both bandwidth protection and no bandwidth protection primary LSPs
Protected S2L Sharing Families: 0
Protected S2L: 0
Protected i/f: Hu0/1/0/0.1 <--- protect link S1
Attribute-set: Not configured
Protection: NHOP <--- NHOP a.k.a. link protection
Unused removal timeout: not running
History:
Tunnel has been up for: 00:14:38 (since Thu Jul 01 11:08:13 GMT+7 2021)
Current LSP:
Uptime: 00:14:38 (since Thu Jul 01 11:08:13 GMT+7 2021)

Path info (IS-IS main level-1):
Node hop count: 1
Hop0: 100.6.0.9 <-- S2
Hop1: 200.1.1.9 <-- R9

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng auto-tunnel backup summary
AutoTunnel Backup Configuration:
Interfaces count: 1
Unused removal timeout: 5m 0s
Configured tunnel number range: 65000-65500

AutoTunnel Backup Summary:
AutoTunnel Backups:
1 created, 1 up, 0 down, 0 unused
1 NHOP, 0 NNHOP, 0 SRLG strict, 0 SRLG preferred, 0 SRLG weighted, 0 BW protected
Protected LSPs:
2 NHOP, 0 NHOP+SRLG, 0 NHOP+BW, 0 NHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2L Sharing Families:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2Ls:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG

Cumulative Counters (last cleared 2d23h ago):
Total NHOP NNHOP
Created: 16 1 15
Connected: 1 1 0
Removed (down): 15 0 15
Removed (unused): 0 0 0
Removed (in use): 0 0 0
Range exceeded: 0 0 0



From the above output, it looks like the router keeps on trying to create NNHOP-BW too (15x NNHOP creation/removal), this will keep on failing due to topology constraint.


We can configure the router to create auto backup for link protection only:

 

mpls traffic-eng
 interface HundredGigE0/1/0/0.1
  auto-tunnel backup
   nhop-only
  !
 !
!

 

 

Configuring Auto Tunnel Backup Bandwidth Protection

So far so good, now let's configure our new feature.
Let's configure 5G as maximum bandwidth that can be protected by the auto backup LSP.
We will configure the auto backup LSP to signal 5G as well during LSP bring up.

 

Note:

Users are free to configure different value for maximum bandwidth and signalled bandwidth.
These values do not need to be the same.
Examples in this article are using same value for maximum bandwidth and signalled bandwidth to prefent confusion.

 

mpls traffic-eng
 interface HundredGigE0/1/0/0.1
  auto-tunnel backup
   nhop-only
   attribute-set auto_bkup_5000M
   bandwidth-protection maximum-aggregate 5000000 <--- new feature, auto backup LSP to protect only up to a specific aggregate bandwidth.
  !
 !
 attribute-set auto-backup auto_bkup_5000M
  signalled-bandwidth 5000000 class-type 0 <--- new feature, auto backup LSP to signal specific bandwidth during LSP bring up.
 !
!



now we see additional auto backup tunnel being created.

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels tabular

Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te1 2 200.1.1.2 200.1.1.1 up Ready Head Inact
tunnel-te2 2 200.1.1.2 200.1.1.1 up Ready Head Inact
*tunnel-te65005 3 200.1.1.9 200.1.1.1 up Inact Head Inact <-- existing NHOP-BW
*tunnel-te65006 2 200.1.1.9 200.1.1.1 up Inact Head Inact <-- new NHOP+BW



Here is a show output for existing NHOP-BW tunnel-te65005:

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels 65005

Name: tunnel-te65005 Destination: 200.1.1.9 Ifhandle:0x20ab6a0 (auto-tunnel backup)
Signalled-Name: autob_R1-Ichitaka-ASR9904_t65005_Hu0_1_0_0.1
Status:
Admin: up Oper: up Path: valid Signalling: connected

path option (autob_nhop_te65005), preference 20, type explicit (autob_nhop_te65005) (Basis for Setup, path weight 10)
Accumulative metrics: TE 10 IGP 10 Delay 300000
path option (autob_nhop_srlg_te65005), preference 10, type explicit (autob_nhop_srlg_te65005) [disabled]
G-PID: 0x0800 (derived from egress interface properties)
Bandwidth Requested: 5000000 kbps CT0
Creation Time: Thu Jul 1 13:55:08 2021 (00:30:35 ago)
Config Parameters:
Bandwidth: 5000000 kbps (CT0) Priority: 7 7 Affinity: 0x0/0xffff
Metric Type: TE (global)
...


Note that now this tunnel is signalled with 5G bandwidth, previously it was signalled with 0 bandwidth.
This is because the new config "signalled-bandwidth <>" is applied to every auto backup under segment HundredGigE0/1/0/0.1 (S1 in figure 6).

And as for the newly created NHOP+BW tunnel-te65006:

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels 65006

Name: tunnel-te65006 Destination: 200.1.1.9 Ifhandle:0x20ab6e0 (auto-tunnel backup)
Signalled-Name: autob_R1-Ichitaka-ASR9904_t65006_Hu0_1_0_0.1
Status:
Admin: up Oper: up Path: valid Signalling: connected

path option (autob_nhop_te65004), preference 20, type explicit (autob_nhop_te65004) (Basis for Setup, path weight 10)
Accumulative metrics: TE 10 IGP 10 Delay 300000
path option (autob_nhop_srlg_te65004), preference 10, type explicit (autob_nhop_srlg_te65004) [disabled]
G-PID: 0x0800 (derived from egress interface properties)
Bandwidth Requested: 5000000 kbps CT0
Creation Time: Thu Jul 1 13:56:37 2021 (00:29:50 ago)
Config Parameters:
Bandwidth: 5000000 kbps (CT0) Priority: 7 7 Affinity: 0x0/0xffff
Metric Type: TE (global)
Path Selection:
Tiebreaker: Min-fill (default)
Hop-limit: disabled
Cost-limit: disabled
Delay-limit: disabled
Delay-measurement: 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:
Fast Reroute: Disabled, Protection Desired: None
Path Protection: Not Enabled
BFD Fast Detection: Disabled
Reoptimization after affinity failure: Enabled
Soft Preemption: Disabled
Auto Backup:
Protected LSPs: 1
Protected S2L Sharing Families: 0
Protected S2L: 0
Protected i/f: Hu0/1/0/0.1
Attribute-set: auto_bkup_5000M
Protection: NHOP+BW
Unused removal timeout: not running
History:
Tunnel has been up for: 00:29:50 (since Thu Jul 01 13:56:37 GMT+7 2021)
Current LSP:
Uptime: 00:29:50 (since Thu Jul 01 13:56:37 GMT+7 2021)

Path info (IS-IS main level-1):
Node hop count: 1
Hop0: 100.6.0.9
Hop1: 200.1.1.9

Displayed 1 (of 4) heads, 0 (of 0) midpoints, 0 (of 0) tails
Displayed 1 up, 0 down, 0 recovering, 0 recovered heads


Several things to note from above output (see the output that is marked bold):
1. This tunnel is signalled with 5G bandwidth
2. This tunnel is a link protection LSP with bandwidth protection ("NHOP+BW").
3. It's using same path as existing NHOP-BW tunnel-te65005.

Let's see what the protection looks like.

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels backup auto-tunnel

tunnel-te65005 (auto-tunnel backup) <--- NHOP-BW
Signalled-Name: autob_R1-Ichitaka-ASR9904_t65005_Hu0_1_0_0.1
Admin: up, Oper: up
Src: 200.1.1.1, Dest: 200.1.1.9, Instance: 3
Fast Reroute Backup Provided:
Protected LSPs: 1 (0 active, 0 soft preempted) <--- not too clear from here, but it's protecting PT-BW tunnel-te2
Protected S2L Sharing Families: 0
Protected S2Ls: 0
Backup BW: any-class (no limit specified), Inuse: 1000000 kbps <--- no maximum-aggregate bandwidth protection
soft preempted: 0 kbps
Protected i/fs: Hu0/1/0/0.1
tunnel-te65006 (auto-tunnel backup) <--- NHOP+BW
Signalled-Name: autob_R1-Ichitaka-ASR9904_t65022_Hu0_1_0_0.1
Admin: up, Oper: up
Src: 200.1.1.1, Dest: 200.1.1.9, Instance: 2
Fast Reroute Backup Provided:
Protected LSPs: 1 (0 active, 0 soft preempted) <--- not too clear from here, but it's protecting PT+BW tunnel-te1
Protected S2L Sharing Families: 0
Protected S2Ls: 0
Backup BW: any-class; limit: 5000000 kbps, Inuse: 1000000 kbps <--- maximum-aggregate bandwidth protection of 5G
soft preempted: 0 kbps
Protected i/fs: Hu0/1/0/0.1

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng auto-tunnel backup
AutoTunnel Backup Configuration:
Interfaces count: 1
Unused removal timeout: 5m 0s
Configured tunnel number range: 65000-65500

AutoTunnel Backup Summary:
AutoTunnel Backups:
2 created, 2 up, 0 down, 0 unused <--- two auto backup LSPs created: 1 NHOP+BW, 1 NHOP-BW.
2 NHOP, 0 NNHOP, 0 SRLG strict, 0 SRLG preferred, 0 SRLG weighted, 1 BW protected <--- both auto backup LSPs are link protection LSP (NHOP).
Protected LSPs:
1 NHOP, 0 NHOP+SRLG, 1 NHOP+BW, 0 NHOP+BW+SRLG <--- two primary LSPs are protected: tunnel-te1 which is a PT+BW, tunnel-te2 which is a PT-BW.
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2L Sharing Families:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2Ls:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG

Cumulative Counters (last cleared 3d01h ago):
Total NHOP NNHOP
Created: 23 7 16
Connected: 7 7 0
Removed (down): 16 0 16
Removed (unused): 2 2 0
Removed (in use): 3 3 0
Range exceeded: 0 0 0


AutoTunnel Backups:
Tunnel              State     Protection       Prot.       Protected      Protected
Name                            Offered           Flows*    Interface       Node
-------------- ------- --------------- ------- --------------- ---------------
tunnel-te65005 up        NHOP              1          Hu0/1/0/0.1 N/A
tunnel-te65006 up        NHOP+BW       1         Hu0/1/0/0.1 N/A <--- Use the NHOP+BW only to protect PT+BW.
*Prot. Flows = Total Protected LSPs, S2Ls and S2L Sharing Families



How about if there is no more room to protect LSPs requesting bandwidth protection? Then we will use the regular auto-tunnel backups to provide FRR protection.
Let's see this in action.

At this moment NHOP+BW tunnel-te65006 is protecting up to 5G of bandwidth.
PT+BW tunnel-te1 is consuming 1G out of that 5G already, leaving 4G remaining for other PT+BW.

Now what happens if there's a new PT+BW coming up requesting bandwidth protection of 5G?
Now let's check the outcome.

 

interface tunnel-te666
ipv4 unnumbered Loopback0
ipv6 enable
signalled-bandwidth 5000000
destination 200.1.1.2
fast-reroute protect bandwidth
path-option 10 explicit name R1_vlan1_R9_R6_R2
!



Newly added PT+BW tunnel-te666 is up, but note that it's being backed up by NHOP-BW tunnel-te65005.
This is because NHOP+BW tunnel-te65006 can't support additional 5G protected bandwidth.

 

RP/0/RSP0/CPU0:Jul 1 17:05:43.884 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-FRR_STATE : tunnel-te666 (signalled-name: R1-Ichitaka-ASR9904_t666, LSP Id: 2, Dest: 200.1.1.2) FRR state changed to FRR-Ready, backup tunnel (tunnel-te65005, LSP Id: 2), protection type (link).
RP/0/RSP0/CPU0:Jul 1 17:05:43.885 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-S2L_SIGNALLING_STATE : tunnel-te666 (signalled-name: R1-Ichitaka-ASR9904_t666,T:666, LSP id: 2, Role: Current, src: 200.1.1.1, dest: 200.1.1.2): signalling state changed to Up

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng auto-tunnel backup
AutoTunnel Backup Configuration:
Interfaces count: 1
Unused removal timeout: 5m 0s
Configured tunnel number range: 65000-65500

AutoTunnel Backup Summary:
AutoTunnel Backups:
2 created, 2 up, 0 down, 0 unused
2 NHOP, 0 NNHOP, 0 SRLG strict, 0 SRLG preferred, 0 SRLG weighted, 1 BW protected
Protected LSPs:
2 NHOP, 0 NHOP+SRLG, 1 NHOP+BW, 0 NHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2L Sharing Families:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2Ls:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG

Cumulative Counters (last cleared 00:14:13 ago):
Total NHOP NNHOP
Created: 3 3 0
Connected: 3 3 0
Removed (down): 0 0 0
Removed (unused): 1 1 0
Removed (in use): 0 0 0
Range exceeded: 0 0 0


AutoTunnel Backups:
Tunnel                    State     Protection     Prot.         Protected   Protected
Name                                  Offered         Flows*      Interface    Node
-------------- ------- --------------- ------- --------------- ---------------
tunnel-te65006 up            NHOP+BW       1          Hu0/1/0/0.1 N/A <--- protecting PT+BW tunnel-te1
tunnel-te65005 up            NHOP              2          Hu0/1/0/0.1 N/A <--- protecting PT-BW tunnel-te2 and PT+BW tunnel-te666
*Prot. Flows = Total Protected LSPs, S2Ls and S2L Sharing Families



Now let's step back and see the case where auto-tunnel backups finds no path that can satisfy the configured signalled bandwidth.

 

mpls traffic-eng
 interface HundredGigE0/1/0/0.1
  auto-tunnel backup
   nhop-only
   no attribute-set auto_bkup_5000M
   attribute-set auto_bkup_10000M
  !
 !
 attribute-set auto-backup auto_bkup_10000M
  signalled-bandwidth 10000000 class-type 0 <--- now asking for 10G instead of 5G
 !
!



We see that the router signals 0 value as bandwidth in order to keep the auto backup operational, afterwhich it will keep on trying to reoptimize to satisfy the bandwidth requirement:

 

RP/0/RSP0/CPU0:Jul 1 21:20:13.603 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-LSP_BW_CHANGE : Bandwidth change on tunnel-te65006 (signalled-name: autob_R1-Ichitaka-ASR9904_t65006_Hu0_1_0_0.1, LSP id: 3): new bandwidth 0 kbps
RP/0/RSP0/CPU0:Jul 1 21:20:13.603 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-LSP_REOPT : tunnel-te65006 (signalled-name: autob_R1-Ichitaka-ASR9904_t65000_Hu0_1_0_0.1, old LSP Id: 2, new LSP Id: 3) has been reoptimized; reason: Bandwidth CLI Change.
RP/0/RSP0/CPU0:Jul 1 21:20:13.604 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-LSP_BW_CHANGE : Bandwidth change on tunnel-te65005 (signalled-name: autob_R1-Ichitaka-ASR9904_t65005_Hu0_1_0_0.1, LSP id: 3): new bandwidth 0 kbps
RP/0/RSP0/CPU0:Jul 1 21:20:13.604 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-LSP_REOPT : tunnel-te65005 (signalled-name: autob_R1-Ichitaka-ASR9904_t65005_Hu0_1_0_0.1, old LSP Id: 2, new LSP Id: 3) has been reoptimized; reason: Bandwidth CLI Change.

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels 65006 | i Bandwidth Req
Bandwidth Requested: 0 kbps CT0
RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels 65005 | i Bandwidth Req
Bandwidth Requested: 0 kbps CT0


Soft-preemption

Soft-preemption configuration in the auto-tunnel backup attribute set is now supported.
Since auto backups now reserve bandwidth, it is important to be able to soft-preempt these backups in case the bandwidth they are reserving is needed by a higher priority tunnel.

We configure soft-preemption through the following config.

 

mpls traffic-eng
 interface HundredGigE0/1/0/0.1
  auto-tunnel backup
   attribute-set auto_bkup_5000M
   ...
   !
  !
 attribute-set auto-backup auto_bkup_5000M
  soft-preemption <--- configure soft-preemption for auto-tunnel (newly supported config in this release)
  ...
 !
 soft-preemption <--- configure soft-preemption for general traffic engineering (existing feature)
 !
!




After configuring the above, we see that soft-preemption is now enabled on both NHOP+BW and NHOP-BW.

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels 65005 | i empt
Soft Preemption: Enabled, Current Status: Preemption not pending
RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels 65006 | i empt
Soft Preemption: Enabled, Current Status: Preemption not pending



Now let's try to preempt our existing auto backups by bringing up a new LSP.

 

interface tunnel-te777
ipv4 unnumbered Loopback0
ipv6 enable
signalled-bandwidth 10000000
destination 200.1.1.9
path-option 10 explicit name R1_vlan2_R9
priority 3 3
soft-preemption <--- This config will make head-end router to indicate to all the intermediate nodes that existing LSP is to be softly preempted when needed
!

 

RP/0/RSP0/CPU0:Jul 2 14:55:44.896 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-LSP_SOFT_PREEMPT : Tunnel 65005 (autob_R1-Ichitaka-ASR9904_t65005_Hu0_1_0_0.1, LSP Id: 6) has been soft preempted at interface Hu0/1/0/0.2 (100.6.0.1), timeout after 60 seconds.
RP/0/RSP0/CPU0:Jul 2 14:55:44.896 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-S2L_SIG_ERR : Signalled error received on tunnel-te65005 (signalled-name: autob_R1-Ichitaka-ASR9904_t65005_Hu0_1_0_0.1, Dest: 200.1.1.9, LSP: 6): SigErr(34,1)-(Error: reroute (34), Suberror: flow soft-preempted (1)) at 100.6.0.1
RP/0/RSP0/CPU0:Jul 2 14:55:44.896 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-LSP_SOFT_PREEMPTED : Tunnel 65005 (autob_R1-Ichitaka-ASR9904_t65005_Hu0_1_0_0.1, LSP Id: 6) has been soft preempted at 100.6.0.1

RP/0/RSP0/CPU0:Jul 2 14:55:44.896 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-LSP_SOFT_PREEMPT : Tunnel 65006 (autob_R1-Ichitaka-ASR9904_t65006_Hu0_1_0_0.1, LSP Id: 6) has been soft preempted at interface Hu0/1/0/0.2 (100.6.0.1), timeout after 60 seconds.
RP/0/RSP0/CPU0:Jul 2 14:55:44.896 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-S2L_SIG_ERR : Signalled error received on tunnel-te65006 (signalled-name: autob_R1-Ichitaka-ASR9904_t65006_Hu0_1_0_0.1, Dest: 200.1.1.9, LSP: 6): SigErr(34,1)-(Error: reroute (34), Suberror: flow soft-preempted (1)) at 100.6.0.1
RP/0/RSP0/CPU0:Jul 2 14:55:44.896 GMT+7: te_control[1085]: %ROUTING-MPLS_TE-5-LSP_SOFT_PREEMPTED : Tunnel 65006 (autob_R1-Ichitaka-ASR9904_t65006_Hu0_1_0_0.1, LSP Id: 6) has been soft preempted at 100.6.0.1


The pre-empted auto backup later will re-signal with 0 bandwidth since it can't find any alternative link to use.

 

RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels 65005 | i Bandwidth Req
Bandwidth Requested: 0 kbps CT0
RP/0/RSP0/CPU0:R1-Ichitaka-ASR9904#sh mpls traffic-eng tunnels 65006 | i Bandwidth Req
Bandwidth Requested: 0 kbps CT0


In the absence of soft-preemption, the auto backups will be torn down right away (i.e. hard preempted) as tunnel-te777 comes up.


Node Protection

 

So far we have described about how an auto-tunnel backup can provide link protection with bandwidth protection, now let's see how it can provide node protection as well.

Back to our diagram in Figure 6, we can create new PT+BW LSP with head end R2 and tail end R1, with path S3-S2-S1.
Then we will have R2 to create an auto-tunnel backup on S5 that provide node protection for R6.

Base configuration on R2:

 

explicit-path name R2_R6_R9_R1
index 1 next-address strict ipv4 unicast 100.4.0.6
index 2 next-address strict ipv4 unicast 100.5.0.9
index 3 next-address strict ipv4 unicast 100.1.0.1
!

interface tunnel-te101
ipv4 unnumbered Loopback0
ipv6 enable
signalled-bandwidth 1000000
destination 200.1.1.1
fast-reroute protect bandwidth
path-option 10 explicit name R2_R6_R9_R1
!


tunnels are up:

 

RP/0/RP0/CPU0:R2-Aiko-NCS5502SE#sh mpls traffic-eng tunnels tabular

Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te101 2 200.1.1.1 200.1.1.2 up Inact Head Inact


Now let's create the auto tunnel backup.
We're aiming to node protect R6 so we need to configure auto-tunnel backup on the interface facing R6, which is S3 Fo0/0/0/40.1.

 

mpls traffic-eng
 interface Fo0/0/0/40.1
  auto-tunnel backup
   attribute-set auto_bkup_5000M
   bandwidth-protection maximum-aggregate 5000000
  !
 !
 attribute-set auto-backup auto_bkup_5000M
  signalled-bandwidth 5000000 class-type 0
 !
!

 

The auto-tunnel backup are now created:

 

RP/0/RP0/CPU0:R2-Aiko-NCS5502SE#sh mpls traffic-eng tunnels tabular

Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te101 2 200.1.1.1 200.1.1.2 up Ready Head Inact
*tunnel-te65000 2 200.1.1.9 200.1.1.2 up Inact Head Inact
*tunnel-te65001 2 200.1.1.9 200.1.1.2 up Inact Head Inact
*tunnel-te65002 0 200.1.1.6 0.0.0.0 down Inact Head Inact
*tunnel-te65003 0 200.1.1.6 0.0.0.0 down Inact Head Inact



Note from the output above that we're creating 4 auto-tunnel backup in one shot:

  1. tunnel-te65000 which is an NNHOP+BW.
    This is the one that we want to have.
  2. tunnel-te65001 which is an NNHOP-BW.
    This is unused since we don't have PT-BW to protect.
  3. tunnel-te65002 which is an NHOP+BW.
    This is down and unused since we don't have alternate link between R2_R6 for link protection.
  4. tunnel-te65003 which is an NHOP-BW.
    This is down and unused since we don't have alternate link between R2_R6 for link protection.

RP/0/RP0/CPU0:R2-Aiko-NCS5502SE#sh mpls traffic-eng auto-tunnel backup
AutoTunnel Backup Configuration:
Interfaces count: 1
Unused removal timeout: 5m 0s
Configured tunnel number range: 65000-65500

AutoTunnel Backup Summary:
AutoTunnel Backups:
4 created, 2 up, 2 down, 3 unused
2 NHOP, 2 NNHOP, 0 SRLG strict, 0 SRLG preferred, 0 SRLG weighted, 2 BW protected
Protected LSPs:
0 NHOP, 0 NHOP+SRLG, 0 NHOP+BW, 0 NHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 1 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2L Sharing Families:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2Ls:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG

Cumulative Counters (last cleared 4d03h ago):
Total NHOP NNHOP
Created: 8 4 4
Connected: 4 0 4
Removed (down): 2 2 0
Removed (unused): 0 0 0
Removed (in use): 2 0 2
Range exceeded: 0 0 0


AutoTunnel Backups:
Tunnel            State          Protection            Prot.           Protected         Protected
Name                               Offered                Flows*        Interface          Node
-------------- ------- --------------- ------- --------------- ---------------
tunnel-te65000 up          NNHOP+BW           1 Fo0/0/0/40.1              200.1.1.6
tunnel-te65001 up          NNHOP                  0 Fo0/0/0/40.1              200.1.1.6
tunnel-te65002 down     NHOP+BW              0 Fo0/0/0/40.1              N/A
tunnel-te65003 down     NHOP                     0 Fo0/0/0/40.1              N/A


The unused tunnels will eventually age out and removed:

 

RP/0/RP0/CPU0:R2-Aiko-NCS5502SE#sh mpls traffic-eng tunnels tabular

Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te101 2 200.1.1.1 200.1.1.2 up Ready Head Inact
*tunnel-te65000 2 200.1.1.9 200.1.1.2 up Inact Head Inact

 

RP/0/RP0/CPU0:R2-Aiko-NCS5502SE#sh mpls traffic-eng auto-tunnel backup
AutoTunnel Backup Configuration:
Interfaces count: 1
Unused removal timeout: 5m 0s
Configured tunnel number range: 65000-65500

AutoTunnel Backup Summary:
AutoTunnel Backups:
1 created, 1 up, 0 down, 0 unused
0 NHOP, 1 NNHOP, 0 SRLG strict, 0 SRLG preferred, 0 SRLG weighted, 1 BW protected
Protected LSPs:
0 NHOP, 0 NHOP+SRLG, 0 NHOP+BW, 0 NHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 1 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2L Sharing Families:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
Protected S2Ls:
0 NHOP, 0 NHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG
0 NNHOP, 0 NNHOP+SRLG, 0 NNHOP+BW, 0 NNHOP+BW+SRLG

Cumulative Counters (last cleared 4d03h ago):
Total NHOP NNHOP
Created: 8 4 4
Connected: 4 0 4
Removed (down): 4 4 0
Removed (unused): 1 0 1
Removed (in use): 2 0 2
Range exceeded: 0 0 0


AutoTunnel Backups:
Tunnel              State          Protection         Prot.           Protected     Protected
Name                                Offered             Flows*         Interface       Node
-------------- ------- --------------- ------- --------------- ---------------
tunnel-te65000 up            NNHOP+BW       1             Fo0/0/0/40.1 200.1.1.6
*Prot. Flows = Total Protected LSPs, S2Ls and S2L Sharing Families

 


MPLS TE Auto Tunnel Backup Bandwidth Protection on transit router

 

Config example given so far is when you configure the feature on head-end router.
The feature can also be configured on transit router.
For example, in Figure 6 with PT+BW having head end router of R1 and path of S1_S2_S3, R9 is a transit router where we can configure the feature as well.
On R9, we can protect the PT+BW by doing node protection for R6, by creating auto tunnel backup on alternate path S5.
When R6 goes down, R9 can switch the traffic from original path S2_S3 to S5.

Configuration is the same as when we configure on head-end router:

config "bandwidth-protection maximum-aggregate" on interface S2 and so on.

 

 

Config Summary

 

The following is a sample of configuration needed to activate Auto Backup Bandwidth Protection feature.
The line that is marked bold is new supported CLI config introduced with the feature.

 

ipv4 unnumbered mpls traffic-eng Loopback0

!

explicit-path name R1_vlan1_R9_R6_R2
index 1 next-address strict ipv4 unicast 100.1.0.9
index 2 next-address strict ipv4 unicast 100.5.0.6
index 3 next-address strict ipv4 unicast 100.4.0.2
!

interface Loopback0
ipv4 address 200.1.1.1 255.255.255.255
!
interface tunnel-te1
ipv4 unnumbered Loopback0
ipv6 enable
signalled-bandwidth 1000000
destination 200.1.1.2
fast-reroute protect bandwidth
path-option 10 explicit name R1_vlan1_R9_R6_R2
!
interface tunnel-te2
ipv4 unnumbered Loopback0
ipv6 enable
signalled-bandwidth 1000000
destination 200.1.1.2
fast-reroute
path-option 10 explicit name R1_vlan1_R9_R6_R2
!
interface HundredGigE0/1/0/0.1
ipv4 address 100.1.0.1 255.255.0.0
encapsulation dot1q 1
!
interface HundredGigE0/1/0/0.2
ipv4 address 100.6.0.1 255.255.0.0
encapsulation dot1q 2
!

router isis main
net 47.0005.1111.1111.1111.00
nsr
distribute link-state
log adjacency changes
address-family ipv4 unicast
 metric-style wide
 mpls traffic-eng level-1-2
 mpls traffic-eng router-id Loopback0
 router-id Loopback0
!
address-family ipv6 unicast
 metric-style wide
 router-id Loopback0
!
interface Loopback0
 passive
 address-family ipv4 unicast
 !
 address-family ipv6 unicast
 !
!
interface HundredGigE0/1/0/0.1
 point-to-point
 address-family ipv4 unicast
 !
 address-family ipv6 unicast
 !
!
interface HundredGigE0/1/0/0.2
 point-to-point
 address-family ipv4 unicast
 !
 address-family ipv6 unicast
 !
!
!
rsvp
 interface HundredGigE0/1/0/0.1
  bandwidth 10000000
 !
 interface HundredGigE0/1/0/0.2
  bandwidth 10000000
 !
!
mpls traffic-eng
 interface HundredGigE0/1/0/0.1
 auto-tunnel backup
  nhop-only
  attribute-set auto_bkup_5000M
  bandwidth-protection maximum-aggregate 5000000
  !
 !
 interface HundredGigE0/1/0/0.2
 !
 logging events all
 auto-tunnel backup
  timers removal unused 5
  tunnel-id min 65000 max 65500
 !
 reoptimize 604800
 attribute-set auto-backup auto_bkup_5000M
  signalled-bandwidth 5000000 class-type 0
  soft-preemption
 !
 soft-preemption
 !
!

 

 

Auto Backup Bandwidth Protection and NSR

 

NSR RP switchover is hitless for both MPLS TE control and data plane, provided all underlay protocol (BGP, ISIS, OSPF, etc) has been configured for NSR.

 

 

Related Show Commands

 

show mpls traffic-eng auto-tunnel backup
show mpls traffic-eng tunnels tabular
show mpls traffic-eng tunnels summary

show rsvp interface


Logs to provide to Cisco TAC for MPLS TE Auto Tunnel Backup Bandwidth Protection issues

 

Gather the following set of logs from the router.
Replace "NAME_OF_ROUTER"with the name of your router.

 

Logs/info to grab:

 

  1. Timestamp when the problem occurs (e.g. Jul 2 10:55:47.015 GMT+7), the more exact, the better.
    It's best if the timestamp can be copied from a specific line of "show log" output.
  2. show tech mpls traffic-eng file harddisk:/NAME_OF_ROUTER_sh_tech_mpls_traffic_eng
  3. show log | file harddisk:/NAME_OF_ROUTER_show_log.txt
    (showing the events when the problem occurs)

 

Article change log

 

2021/06/03: First post of this article.
2021/06/07: Putting a note in "Configuring Auto Tunnel Backup Bandwidth Protection" section that maximum bandwidth and signalled bandwidth don't need to be same value.