802.3 requires 1000BASE-T interface to do autonegotiation. But many network gear can disable autoneg and force 1000M-FDX operation for 1000BASE-T interface (such as "no autonegotiation / duplex full / speed 1000" ).
Despite that the spec requires autoneg and many gear venders also recommend to enable autoneg, my colleague insists on disabling autoneg. He prefer fixed configuration because autoneg-enabled 1000-T port sometimes "falls back" into 100/10M mode due to bad cable (for example one of 8 wires in Cat5 cable is cut).... Furthermore autoneg-disabled 1000BASE-T link in our lab is apparently working well.
My question: Does something wrong occur if I set "no autoneg" to each end of 1000BASE-T port? (e.g. BER increase or link flap ?)
AFAIK 1000BASE-X's autoneg includes remote fault signalling which detects uni-directional fiber cut. It makes senses to enable autonegotiation for all 1000BASE-X link.