Troubleshooting Layer 3—IP routing

Troubleshooting RIR

The highest-priority link not selected for traffic forwarding

Symptom

In priority-based link selection, RIR does not select the link with the highest priority (Tunnel 1) for service traffic. Instead, it selects the link with second highest priority (Tunnel 2) for traffic forwarding.

Common causes

The following are the common causes of this type of issue:

·     The route associated with the highest-priority link is unreachable.

·     No ECMP routes are available to the destination IP address of service traffic.

·     The bandwidth usage of the highest-priority link exceeds the specified lower threshold.

·     The quality of the highest-priority link does not meet the requirements.

Analysis

Figure 1 shows the troubleshooting flowchart.

Figure 1 Flowchart for troubleshooting failure to select the highest-priority link for traffic forwarding

 

Solution

1.     Identify whether the route associate with the highest-priority link (Tunnel 1) is reachable.

a.     Execute the display tunnel flow-statistics command to view the path information (Interface) selected for the service traffic, namely Tunnel 2.

<Sysname> display tunnel flow-statistics flow 100

 

Flow 100:

  Interface    Out pps       Out bps

  Tunnel2      20            9600

b.     Execute the display ip fast-forwarding cache command to view the 5-tuple information of the service traffic (that is, the output interface is Tunnel 2), and obtain the destination IP address of the service traffic.

<Sysname> display ip fast-forwarding cache

Total number of fast-forwarding entries: 1

SIP            SPort DIP            DPort Pro Input_If   Output_If   Flg

7.0.0.13       68    8.0.0.1        67    17  GE1/0/3    Tunnel2     5

c.     Execute the display fib command to identify whether ECMP routes are available to the destination IP address, and the ECMP routes include link Tunnel 1.

-     If no ECMP routes are available, check and edit route configuration to ensure that ECMP routes are available to the destination IP address and include link Tunnel 1. Only when such conditions exist, Tunnel 1 can participate in RIR route selection.

-     If the ECMP routes exist, proceed to step 2.

<Sysname> display fib

Route destination count: 5

Directly-connected host count: 0

 

Flag:

  U:Useable   G:Gateway   H:Host   B:Blackhole   D:Dynamic   S:Static

  R:Relay     F:FRR

 

Destination/Mask   Nexthop         Flag     OutInterface/Token       Label

8.0.0.1/32         127.0.0.1       UH       Tunnel1                  Null

8.0.0.1/32         127.0.0.1       UH       Tunnel2                  Null

2.     Examine the bandwidth usage of the highest-priority link Tunnel 1.

a.     Identify the bandwidth threshold. Verify that the flow priority-based-schedule enable command is configured in RIR-SDWAN view. If the command is not configured, the lower bandwidth usage threshold is 80%. If the command is configured, the lower bandwidth usage threshold is specified by the flow priority-based-schedule bandwidth-threshold command (default is 20%).

b.     Execute the display rir sdwan bandwidth tunnel command to identify whether the bandwidth usage of Tunnel 1 exceeds the lower bandwidth threshold.

-     If the lower bandwidth threshold is not exceeded, the bandwidth meets the link selection criteria, and you can proceed to step 3.

-     If the lower bandwidth threshold is exceeded, the bandwidth does not meet the route selection criteria. Verify that the bandwidth of Tunnel 1 matches the bandwidth of the tunnel's physical output interface. If they do not match, edit the bandwidth of Tunnel 1 with the bandwidth command. If they match, it is normal for RIR to select Tunnel 2, because the bandwidth usage of Tunnel 1 does not meet the route selection criteria. Therefore, the device schedules service traffic to the lower-priority link Tunnel 2.

<Sysname> display rir sdwan bandwidth tunnel 1

Tunnel bandwidth info:

  Interface      Total bandwidth    Remaining bandwidth    Bandwidth usage

  Tunnel1        200 kbps           200 kbps               0 %

Output interface bandwidth info:

  PeerTTE: SiteID=1 DeviceID=2 IfID=2                      

    Interface      Total bandwidth    Remaining bandwidth    Bandwidth usage

    GE1/0/1        200 kbps           200 kbps               0 %

3.     Examine the quality of the highest-priority link Tunnel 1.

a.     Execute the display rir sdwan flow command to verify that the CQI value for Tunnel 1 reaches 100.

-     If the CQI value is 100, proceed to step 4.

-     If the CQI value is below 100, proceed to step b.

<Sysname> display rir sdwan flow 1

Flow ID: 1

Session expected bandwidth: 2000 kbps

Quality policy: Yes

Tunnels with different preference values:

  Preference: 8

    Tunnel1

      Site ID   Device ID   Interface ID      CQI

      100       1           100               80

      100       2           110               90

b.     Execute the display rir sdwan link-quality command to view the packet loss ratio (PktLoss (per mill)), delay (Delay (msec)), and jitter (Jitter (msec)) of Tunnel 1.

<Sysname> display rir sdwan link-quality

Tunnel1

Interface ID=1

 Peer TTE: Site ID=1   Device ID=2   Interface ID=3   

Connectivity: Connected

PktLoss (per mill): 0

Delay (msec)      : 0

Jitter (msec)     : 0

c.     Compare the packet loss ratio, delay, and jitter of Tunnel 1 with the packet loss threshold (configure with the packet-loss threshold command), delay threshold (configure with the delay threshold command), and jitter threshold (configure with the jitter threshold command) configured in RIR-SDWAN view. If any of the thresholds is exceeded, the quality of the link Tunnel 1 does not meet the link selection criteria, and it is normal for RIR to select Tunnel 2. The device will then schedule service traffic to the link Tunnel 2, whose link quality meets the link selection criteria.

d.     To fast restore the CQI value of link Tunnel 1 to 100, you can increase the values for the packet loss threshold (configure with the packet-loss threshold command), delay threshold (configure with the delay threshold command), and jitter threshold (configure with the jitter threshold command) configured in RIR-SDWAN view in the RIR-SDWAN view. This ensures that the quality of the link Tunnel 1 meets the link selection criteria.

4.     If the issue persists, collect the following information and contact Technical Support:

¡     Results of each step.

¡     The configuration file, log messages, and alarm messages.

Related alarm and log messages

Alarm messages

N/A

Log messages

N/A