Cables changed and just got 358/68.

Many thanks to all.

H

In reply to a post by Taras:

a decent cat5e cable can do 10gbits at short distances

Just curious- how does a router (or whatever) work out what sort of cable it's connected to?

Counting pairs is easy enough, but it would get the same answer from the right number of flat twins- not exactly gigabit capable. Does it do some checks of crosstalk or something?

Apparently, 4 core is good for 100Mb/s. I would think that OP's network adaptor or router would see the unbalanced circuits and settle for 100Mb/s. Perhaps OP could look at the connector or use a continuity tester or even sacrifice the cable, they could confirm 4 cores?

NBASE-T autonegotiaton is described here https://ethernetalliance.org/wp-content/uploads/2024...

A quick scan through that suggests a "I wish I hadn't asked" response, but I'll go through it more carefully when I've got more time, thanks 👍

As others have said, change the Ethernet cable. Cat5e is fine but if one of the pairs is broken (or less likely, incorrectly wired) it won't run at 1Gbps, but may run at 100Mbps.
Also check settings on router and computer to make sure it's on "Auto" speed/duplex.

seb

Basically the two ends talk and decide what they can do, and there's a mechanism for downgrading if link errors are detected. So it would be unwise to connect a PC to a switch at 10Gb if the cabling isn't up to it because each time the PC wakes up it will attempt to link at 10Gb and cause you interruptions as it drops out and downgrades, either set the switch port to a lower speed or fix the cable.

In reply to a post by jpm:

Basically the two ends talk and decide what they can do, and there's a mechanism for downgrading if link errors are detected.

That's interesting: so if a router capable of up to 100Mbps over WAN is connected to an ONT then the ONT auto-negotiates the correct output, although not an error as such? My Billion router's EWAN port only accepts up to 100Mbps and runs quite happily from the ONT.

Obviously the router is a potential bottleneck since both the ONT and pc are capable of 1Gbps but at the moment 80Mbps FTTP is more than adequate for my needs.

In reply to a post by jpm:

Basically the two ends talk and decide what they can do, and there's a mechanism for downgrading if link errors are detected. So it would be unwise to connect a PC to a switch at 10Gb if the cabling isn't up to it because each time the PC wakes up it will attempt to link at 10Gb and cause you interruptions as it drops out and downgrades, either set the switch port to a lower speed or fix the cable.

I presume something like the handshake we had at dial up, but constant.
I remember those days,

In reply to a post by MattJessop:

That should sort it

Cat 5 tops out at 100 Mbps, Cat 5e at 1000 Mbps and cat 6 at 10 gigabits.

Over a couple of meters, I'd expect Cat 5 would work fine (and most Cat 5 you buy these days meets Cat 5e specifications anyway)

However if it's a "crossover" cable then it will only work at 100M. If it has only two pairs wired, ditto.

Or it could just be a faulty pin. As long as pins 1,2,3 and 6 are wired, then it'll negotiate down to 100M.