4.5. Network Interface Card speed issues

4.5.1. Normal operation

The negotiated Ethernet links on the network interfaces should be stable and the interface error counters should not increase. The status and the counters can be seen with the command show interfaces <interface name>.

The counters in this output are cumulative since the start-up of the appliance and they can be reset to zero with the command clear interfaces.

Figure 4.5. The output of "show interfaces primary"

SH # show interfaces primary
Interface primary state
   Up:                 yes
   Interface type:     ethernet
   IP address:         10.17.6.119
   Netmask:            255.255.255.128
   IPv6 address:       2001:44b8:7bf1:a50:d69a:20ff:fec2:520e/64
   IPv6 auto-assigned: fe80::20e:b6ff:fe31:45e0/64
   Speed:              100Mb/s (auto)
   Duplex:             full (auto)
   MTU:                1500
   HW address:         00:0E:B6:31:45:E0

   RX bytes:           104060364
   RX packets:         660069
   RX mcast packets:   0
   RX discards:        0
   RX errors:          0
   RX overruns:        0
   RX frame:           0

   TX bytes:           3658160
   TX packets:         33089
   TX discards:        0
   TX errors:          1
   TX overruns:        0
   TX carrier:         1
   TX collisions:      0

The following fields are important:

  • Up: Shows the administrative status of the network interface. Yes means that the interface is enabled.

  • Speed: The value is the speed used by the network interface. If the value contains the string (auto), then the speed is negotiated, otherwise it is a fixed speed.

  • Duplex: The value is the duplex setting used by the network interface. If the value contains the string (auto), then the duplex is negotiated, otherwise it is a fixed duplex setting.

  • MTU: The MTU size defined on this network interface.

  • RX bytes / RX packets / TX bytes / TX packets: The number of packets, sent and received, and the total number of bytes of data, sent and received.

  • RX discards / RX errors / RX frame: Number of Ethernet frames which could not be processed because the Ethernet frame was corrupted.

  • TX discards / TX errors / TX carrier / TX collisions: Number of Ethernet frames which could not be sent because of Ethernet layer related problems.

  • RX overruns / TX overruns: Number of Ethernet frames which could not be processed because the NIC ran out of memory to store incoming frames or wasn't fast enough with the processing of frames the buffer.

4.5.2. Possible causes of TX and RX errors

4.5.2.1. Negotiation issues

The Ethernet specification states that if no Ethernet link can be negotiated that the network interface speed should be set to 10 Mbps and the duplex should be set to half-duplex.

This situation can happen when one side of the Ethernet link is set to a fixed duplex/speed and the other side is set to auto-negotiation.

Figure 4.6. Interface set for auto-negotiation but coming up as half-duplex

SH # show interfaces lan0_0
Interface lan0_0 state
   Up:                 yes
   Interface type:     ethernet
   Speed:              10Mb/s (auto)
   Duplex:             half (auto)
   MTU:                1500
   HW address:         00:0E:B6:8C:7A:EE
   Link:               yes

Alternatively when the NIC on the Steelhead appliance is set to a fixed speed and duplex but it receiving a lot of RX/TX errors in the counters:

Figure 4.7. Interface set for fixed speed but with a lot of RX/TX errors

SH # show interfaces lan0_0
Interface lan0_0 state
   Up:                 yes
   Interface type:     ethernet
   Speed:              100Mb/s
   Duplex:             full
   MTU:                1500
   HW address:         00:0E:B6:8C:7A:EE
   Link:               yes

   RX bytes:           104060364
   RX packets:         660069
   RX mcast packets:   0
   RX discards:        0
   RX errors:          12737
   RX overruns:        0
   RX frame:           12737

   TX bytes:           3658160
   TX packets:         33089
   TX discards:        0
   TX errors:          19244
   TX overruns:        0
   TX carrier:         6921
   TX collisions:      12323

These RX/TX counters are cumulative so make sure they are actually increasing before drawing conclusions about them.

4.5.2.2. Cable and switch port related issues

If the issue cannot be resolved by fixing the speed / duplex mismatch, consider a replacement of the cables.

If that doesn't overcome the problem, try a different port on the LAN switch or the WAN router and see if the problem migrates to the new port.