SNMPv2c based discovery fails due to use of get-bulk SNMP requests.
By design CAPM uses get-bulk for SNMPv2c requests. This provides better/faster response for larger tables in modern network devices.
Many older network devices also running older firmware either outright don't support get-bulk, or do support it but perform very poorly when trying to respond to these types of requests.
When we see failure of any kind for get-bulk, we default back to trying with SNMPv1, where it often works due to use of get-next.
In many cases the devices will respond to get-next via SNMPv2c. But due to how we default at failure of get-bulk, we succeed for v1 get-next. The problem is when it comes to many things, especially interfaces, we don't get the correct data for the high speed interfaces (v1 only supports the low speed interface table).
The code change implemented by engineering solves this problem. It now takes the following steps:
This fix will make it into r3.1 and also the next monthly update kit for r3.0, likely the February kit.
Note doing so will require they upgrade next to a minimum of r3.1 or the r3.0 or newer February kit (or whatever month kit it makes it into). Updating to any release prior to those would remove the new code that resolves this.
After the fix was installed, we can observe the get-bulk failure followed by the switch to try using the SNMPv2c get-next request method.
Jan 25 18:07:29.788: Column 184.108.40.206.220.127.116.11.1.3 has 1 entries with reading error: SUCCESS
Jan 25 18:07:29.788: DEBUG Send on-demand request for table 1 with maximum repetitions 10: [18.104.22.168.22.214.171.124.1.6, 126.96.36.199.188.8.131.52.1.5, 184.108.40.206.220.127.116.11.1.7, 18.104.22.168.22.214.171.124.1.3, 126.96.36.199.188.8.131.52.1.8, 184.108.40.206.220.127.116.11.1.2, 18.104.22.168.22.214.171.124.1.1]
Jan 25 18:07:29.874: DEBUG Got RESOURCE_NOT_AVAILABLE error
Jan 25 18:07:29.874: SNMP error 13 for column 126.96.36.199.188.8.131.52.1.6 that already has 0 rows. Re-read table=true
Jan 25 18:07:29.875: SNMP error 13 for column 184.108.40.206.220.127.116.11.1.1 that already has 0 rows. Re-read table=true
Jan 25 18:07:29.875: Re-read table 1 with GetNext method.
Jan 25 18:07:29.875: DEBUG Use GetNext to read table 1 with OIDs: [18.104.22.168.22.214.171.124.1.6, 126.96.36.199.188.8.131.52.1.5, 184.108.40.206.220.127.116.11.1.7, 18.104.22.168.22.214.171.124.1.3, 126.96.36.199.188.8.131.52.1.8, 184.108.40.206.220.127.116.11.1.2, 18.104.22.168.22.214.171.124.1.1]
Jan 25 18:08:16.898: Read completed for table 1
Jan 25 18:08:16.898: Column 126.96.36.199.188.8.131.52.1.6 has 28 entries with reading error: SUCCESS
Jan 25 18:08:16.898: Column 184.108.40.206.220.127.116.11.1.2 has 169 entries with reading error: SUCCESS