The ISP circuit or LAN interface is not auto-negotiating properly

Description - An interface on the Bigleaf router or connected ISP or LAN network device has negotiated a lower than expected speed or half-duplex.

Indicators of this issue

  • Slower than expected throughput at a site or through a specific ISP circuit.

  • The Bigleaf router connected interface on the firewall or ISP equipment shows a high number of errors or half-duplex.

Potential Causes

  • Misalignment of port configuration

  • Faulty or out of date drivers fail to properly communicate auto-negotiation

  • Cabling or NIC problems

Tests and Solutions

  • Verify the port status on both ISP devices and/or the downstream LAN device from the Bigleaf router.

  • To resolve the issue depending on observed symptoms or data gathered:

    • Ingress CRC / framing errors indicate a layer-1 problem on the link itself or perhaps on the next link connected to a media converter. Change network ports if available and replace the cable(s).

    • Auto-negotiation is mandatory for Gigabit Ethernet per IEEE 802.3 standards, and it is optional with 100Mbps Fast Ethernet interfaces. If a port has auto-negotiated successfully, do not hard-code it to 100Mbps full-duplex.

    • If a gigabit interface auto-negotiates to 100Mbps speed, replace the network cable. Typically, this indicates one of the twisted pairs is faulty in the cable.

    • If a link is at 100Mbps for any reason, you cannot expect its speeds to exceed 100Mbps. So a 200Mbps circuit, for example, could be limited by the negotiated link speed.

  • There is a known issue with BLR-108 ports WAN1 and WAN2 failing to auto-negotiate to 100Mbps with some legacy ISP equipment. 

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