2 x Asus XG-C100C, PC to PC, can't talk to each other.

[Axle Grease]

PC A has an Asus Rampage V Extreme Edition 10 with the latest BIOS.
PC B has an Aaus X399 Prime A with the latest BIOS.
OS is WIndows !0 on both PCs, fully updated.

My flatmate has two Asus XG-C100C 10Gb network cards connected using a CAT 6a cable. They don't "see" each other when connected using a cable PC to PC. The packets time out when pinged from either end.

When he adds a 1Gb switch between the cards, they can communicate.

When he removes the switch and connects the cards PC to PC again, AND forces the cards to 1Gb speed, they can no longer communicate.

When he connects a cable between the XG-C100C on PC A and an integrated Intel I211 on PC B they fail to communicate, however they can communicate via his 1Gb switch.

When he connects a cable between the XG-C100C on PC B and an integrated Intel I218 on PC A they fail to communicate, however they can communicate via his 1Gb switch.

We tried different cables with no success.

Now, get this. When using a PC to PC connection using integrated 1Gb ethernet only, STILL both sides can't communicate except through the 1Gb switch.

What's happening doesn't makes sense. What voodoo does the switch do that enables both sides to see each other?

[MasterC@ROG]

You won't be able to establish a connection between two PCs by a single Ethernet cable without doing a little homework.
Routers and switches (hubs do not) help to make each PC in your network identifiable to each other by assigning an IP address and other network configuration parameters. Without either of them, you'll need to assign the settings manually.

There are many YouTube tutorials to refer to.

[Axle Grease]

You won't be able to establish a connection between two PCs by a single Ethernet cable without doing a little homework.
Routers and switches (hubs do not) help to make each PC in your network identifiable to each other by assigning an IP address and other network configuration parameters. Without either of them, you'll need to assign the settings manually.

There are many YouTube tutorials to refer to.

We've assigned a class C non-routable IP address of 192.168.1.1 and .1.2 respectively, both with a netmask 255.255.255.0. No gateway or DNS as that shouldn't be required. In all cases and regardless of NIC used, and with or without a firewall, the result was the same.

[Arne Saknussemm]

[xeromist]

We've assigned a class C non-routable IP address of 192.168.1.1 and .1.2 respectively, both with a netmask 255.255.255.0. No gateway or DNS as that shouldn't be required. In all cases and regardless of NIC used, and with or without a firewall, the result was the same.

Modern network devices are *supposed* to auto negotiate the link and adapt the physical connection in software but it may not be happening here. The ports on switches are cross-wired vs a NIC so they actually aren't the same. Back in the day we needed to use a crossover cable when connecting two NICs directly or two switches without using an uplink port. That was largely eliminated by modern implementations but I still keep a few adapters around just in case.

So it shouldn't be necessary but you might want to try one of these adapters:
https://www.amazon.com/Cables-Unlimi...rnet+crossover
Yes I realize you might not be able to get this specific one from Amazon US but hopefully you have a source on your side of the world that carries these. Just search for "crossover cable" or "ethernet crossover"

[Axle Grease]

Modern network devices are *supposed* to auto negotiate the link and adapt the physical connection in software but it may not be happening here. The ports on switches are cross-wired vs a NIC so they actually aren't the same. Back in the day we needed to use a crossover cable when connecting two NICs directly or two switches without using an uplink port. That was largely eliminated by modern implementations but I still keep a few adapters around just in case.

So it shouldn't be necessary but you might want to try one of these adapters:
https://www.amazon.com/Cables-Unlimi...rnet+crossover
Yes I realize you might not be able to get this specific one from Amazon US but hopefully you have a source on your side of the world that carries these. Just search for "crossover cable" or "ethernet crossover"

The NICs are supposed to be MDIX compatible. What's weirder is that my flatmate got out his old laptop, which has a Realtek ethernet controller, and it can talk to the XG-C100Cs using a straight cable. ...but the NICS can't talk to each other. It also can talk to the I218 on
his R5E Ed10 and the I211 on is X399 Prime A …but the I218 and the I211 can't talk to each other. It's enough to drive oneself batty.

Thanks for your suggestion. I passed it on to my flatmate and he's now at least *thinking* about getting a crossover cable/adapter.

[1mluer]

Its called a Ethernet crossover cable.. that will allow the connection..