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Troubleshooting Guide

CloudEngine 16800, 12800, 12800E, 8800, 7800, 6800, and 5800 Series Switches

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Association Between NQA and Static Route Configured on the Network Egress Device Does Not Take Effect

Association Between NQA and Static Route Configured on the Network Egress Device Does Not Take Effect

In this case, on the egress device of a network, NQA is configured to test active link connectivity and is associated with static route. However, when the active link fails, the routes are not updated automatically.

Networking Description

As shown in Figure 21-2, two CE6850 switches form a stack, which functions as the egress of a data center network connecting to a carrier network. The carrier network provides two links to connect to the data center network, one of which is the active link and the other is the backup link. Two links are not directly connected to the stack. Instead, they are connected to two hosting S9300 switches, and the S9300 switches are connected to the stack. To ensure that traffic from the stack can quickly switch to the backup link when the upstream link of the S9300 connected to the active link fails, the NQA test and association with static route need to be configured on CE6850 switches. The carrier device's IP address needs to be specified as the destination address in the NQA test.

Figure 21-2 Association between NQA and static route

Fault Symptom

When the upstream link of the S9300 connected to the active link fails, the NQA function on the CE6850 does not take effect. That is, the default route of the stack is still destined for the active link, causing service interruption.

Cause Analysis

  1. When the upstream link of the S9300 connected to the active link fails, check the routing tables on CE6850 switches. The route on active link is not switched. The possible reason is that the association between NQA and static route does not take effect.
  2. Run the display nqa history command on a CE6850 to view NQA history information. The command output shows that NQA works normally.
    [~CE6850-1] display nqa history
    T/H/P = Test ID/Hop ID/Probe ID
    NQA entry(NQA, NQA1) history:
    -----------------------------------------------------------------------------------------
    Index T/H/P       Response(ms) Status   Address         Time
    -----------------------------------------------------------------------------------------
     1    300/1/1             1000 timeout  192.168.20.28   2015-10-29 03:43:25.530
     2    301/1/1             1000 timeout  192.168.20.28   2015-10-29 03:43:27.535
     3    302/1/1             1000 timeout  192.168.20.28   2015-10-29 03:43:29.534
     4    303/1/1             1000 timeout  192.168.20.28   2015-10-29 03:43:31.537
     5    304/1/1             1000 timeout  192.168.20.28   2015-10-29 03:43:33.528
     6    305/1/1             1000 timeout  192.168.20.28   2015-10-29 03:43:35.528
     7    306/1/1             1000 timeout  192.168.20.28   2015-10-29 03:43:37.531
     8    307/1/1             1000 timeout  192.168.20.28   2015-10-29 03:43:39.531
     9    308/1/1             1000 timeout  192.168.20.28   2015-10-29 03:43:41.532     
  3. Run the display nqa results command on a CE6850 to view the NQA running result. In the command output, no result is displayed for every NQA probe. This indicates that the association between NQA and static route does not take effect.
    [~CE6850-1] display nqa results
     NQA entry(NQA, NQA1): test flag is active, test type is ICMP
      1 . Test 351 result   The test is finished
       Send operation times: 1                Receive response times: 0
                         RTD over thresholds number: 0
       Attempts number: 1                     Drop operation number: 0
       Disconnect operation number: 0         Operation timeout number: 1
       System busy operation number: 0        Connection fail number: 0
       Operation sequence errors number: 0    RTT Status errors number: 0
       Destination IP address: 192.168.20.28
       Min/Max/Average completion time: 0/0/0
       Sum/Square-Sum  completion time: 0/0
       Last response packet receiving time: 0000-00-00 00:00:00.0
       Lost packet ratio: 100 %
      2 . Test 352 result   The test is finished
       Send operation times: 1                Receive response times: 0
                         RTD over thresholds number: 0
       Attempts number: 1                     Drop operation number: 0
       Disconnect operation number: 0         Operation timeout number: 1
       System busy operation number: 0        Connection fail number: 0
       Operation sequence errors number: 0    RTT Status errors number: 0
       Destination IP address: 192.168.20.28
       Min/Max/Average completion time: 0/0/0
       Sum/Square-Sum  completion time: 0/0
       Last response packet receiving time: 0000-00-00 00:00:00.0
       Lost packet ratio: 100 %
      3 . Test 353 result   The test is finished
       Send operation times: 1                Receive response times: 0
                         RTD over thresholds number: 0
       Attempts number: 1                     Drop operation number: 0
       Disconnect operation number: 0         Operation timeout number: 1
       System busy operation number: 0        Connection fail number: 0
       Operation sequence errors number: 0    RTT Status errors number: 0
       Destination IP address: 192.168.20.28
       Min/Max/Average completion time: 0/0/0
       Sum/Square-Sum  completion time: 0/0
       Last response packet receiving time: 0000-00-00 00:00:00.0
       Lost packet ratio: 100 %    

    After association between NQA and static route is configured on a device, the device deletes the corresponding static route from the IP routing table only after NQA detects a link failure (Completion is fail). However, when Completion is no result, it indicates that the NQA test is in progress and no result is returned. Therefore, the association fails, and the device does not switch routes.

  4. Check the NQA configuration on the CE6850. The information shows that the NQA test packet sending interval (interval) is 1s, the NQA test execution interval (frequency) is 2s, and the NQA test timeout interval (timeout) is 1s.
    # 
    nqa test-instance NQA NQA1 
     test-type icmp 
     destination-address ipv4 192.168.20.28 
     source-address ipv4 192.168.40.28 
     interval seconds 1 
     timeout 1 
     frequency 2 
     start now 
    # 
    ip route-static 0.0.0.0 0.0.0.0 10.1.11.28 preference 40 track nqa NQA NQA1   //Active link route
    ip route-static 0.0.0.0 0.0.0.0 10.1.12.28                                    //Backup link route

    By default, the number of packets sent in each NQA probe (probe-count) is 3. If every probe packet is responded to or no response is returned within timeout, an NQA test result is returned. However, in this case, the NQA test result is always no result. The time required for one NQA probe is 3s (interval*probe-count = 1*3), whereas the NQA test execution interval is 2s. That is, a new NQA probe starts when the previous probe has past 2s. In this situation, the previous probe is in progress, and no result is recorded.

    The cause in this case is that the NQA test execution interval is not appropriate.

Procedure

When configuring an ICMP test instance, pay attention to the following constraints on the timeout, probe-count, frequency, and interval settings:

  • The value of interval (NQA probe packet sending interval) must be larger than the value of timeout (time of one probe).
  • The value of frequency must be larger than interval*probe-count (NQA probe packet sending interval*number of packets sent in each NQA test).

Change the settings of frequency, interval, and timeout by referring to the preceding constraints.

Modified NQA configuration:

# 
nqa test-instance NQA NQA1 
 test-type icmp 
 destination-address ipv4 192.168.20.28
 souter-address ipv4 192.168.40.28
 interval seconds 30 
 frequency 120 
 start now 

Conclusions and Suggestions

  • An NQA probe is successful only when the parameters of the NQA test instance meet conditions.
  • NQA is a second-level probe technology. To increase probe speed, use BFD to replace it.
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Updated: 2020-01-07

Document ID: EDOC1000060766

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