Description:
In a stack of XS and/or GS-45xx switches, the additional administration overhead on the stack master causes an increased CPU load compared to the other stack members.
This article describes how to check the current CPU load on an XS- and GS-45xx series switch and how to optimize the CPU load.
Layer-2 and layer-3 traffic is not processed by the CPU on XS- and GS-45xx series switches. Data transfer is therefore unaffected by a high CPU load!
Requirement:
- SSH client for command-line access (e.g. PuTTY)
Reading-out CPU load on an XS- or GS-45xx-series switch
1) Connect to the stack via SSH and enter the command enable to gain extended privileges.
2) Enter the command terminal length 0 to display any number of lines. Otherwise any lines beyond the default 24 lines will require the <Enter> key to be pressed to display them.
3) Enter the command show process cpu x where x stands for the number of the stack master (in this example show process cpu 4). This command displays a list of active processes along with the current CPU load.
Processes with potentially high CPU load in a stack:
- netsnmp_app with the related RPC thread 00050:
- The load from these two processes increases significantly when monitoring data is reported to the LMC (only affects the stack master). This process only runs periodically so it will only cause temporary load peaks.
- bcmRx:
- This process transfers management information in a stack (affects all switches in a stack).
Optimization options and recommendations for action:
Significantly increased CPU load on GS-45xx switches in a stack managed by the LMC:
Up to and including LCOS SX 5.20 RU6, the CPU load of the stack master in an LMC managed stack of GS-45xx switches is significantly increased (stack members are unaffected). This is because the stack master reports the status information of the other stack members to the LMC and this entails additional administrative effort. This can lead to limited access to the stack-master management interface. However, data transfer is not affected at any time.
This is fixed as of LCOS SX 5.20 RU7. LANCOM Systems recommends that any stack of GS-45xx switches managed by the LMC should be updated to LCOS SX as of version 5.20 RU7 (download current version).
Check CPU load after activating additional features:
Additional features such as dynamic routing protocols (BGP and OSPF), DHCP snooping and RADIUS are processed by the CPU and therefore can have an indirect impact on data traffic. LANCOM Systems therefore recommends that you check the CPU load after activating a feature to see whether the load increases to an extent which slows down the transmission of data traffic.
| Process name | Function |
|---|---|
| ospf_app | OSPF |
| DHCP_snoop | DHCP-Snooping |
| DHCPv6_snoop | DHCPv6-Snooping |
| radius_task | RADIUS |
