# unable to connect 2 b2b devices

## Adel Ahmed

I  have 2 gentoo boxes, I have connected them b2b using eth0 interface on both machines

ethtool cannot identify the cconnection, the ethernet devices themselves are not detecting a connection(the lights do not go on)

If I take either end of the cable and connect it to another device(a router for example) the lights begin blinking and a connection is established

I have no idea what might be causing this problem so I thought I'd ask here

thankks 

pc ~ # ethtool eth0

Settings for eth0:

	Supported ports: [ TP MII ]

	Supported link modes:   10baseT/Half 10baseT/Full 

	                        100baseT/Half 100baseT/Full 

	                        1000baseT/Half 1000baseT/Full 

	Supported pause frame use: No

	Supports auto-negotiation: Yes

	Advertised link modes:  10baseT/Half 10baseT/Full 

	                        100baseT/Half 100baseT/Full 

	                        1000baseT/Half 1000baseT/Full 

	Advertised pause frame use: Symmetric Receive-only

	Advertised auto-negotiation: Yes

	Speed: 10Mb/s

	Duplex: Half

	Port: MII

	PHYAD: 0

	Transceiver: internal

	Auto-negotiation: on

	Supports Wake-on: pumbg

	Wake-on: g

	Current message level: 0x00000033 (51)

			       drv probe ifdown ifup

	Link detected: no

b5400 ~ # ethtool eth0

Settings for eth0:

	Supported ports: [ TP MII ]

	Supported link modes:   10baseT/Half 10baseT/Full 

	                        100baseT/Half 100baseT/Full 

	                        1000baseT/Half 1000baseT/Full 

	Supported pause frame use: No

	Supports auto-negotiation: Yes

	Advertised link modes:  10baseT/Half 10baseT/Full 

	                        100baseT/Half 100baseT/Full 

	                        1000baseT/Full 

	Advertised pause frame use: Symmetric Receive-only

	Advertised auto-negotiation: Yes

	Speed: 10Mb/s

	Duplex: Half

	Port: MII

	PHYAD: 0

	Transceiver: internal

	Auto-negotiation: on

	Supports Wake-on: pumbg

	Wake-on: d

	Current message level: 0x00000033 (51)

			       drv probe ifdown ifup

	Link detected: no

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## NeddySeagoon

Adel Ahmed,

You probably need a crossover cable.

Some things auto detect. Some don't.

-- edit --

Those are 1000M capable.  They should auto detect.

You will need to statically assign addresses to each end.

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## Adel Ahmed

thanks for the assistance, the wierdest thing happened though, I plugged in the cable and communication is working just fine

I do have another concern though, both devices are gigbit ethernet devices

unfortunately the device on the laptop advertises 10 and 100 megabits only:

b5400 ~ # ethtool eth0

Settings for eth0:

	Supported ports: [ TP MII ]

	Supported link modes:   10baseT/Half 10baseT/Full 

	                        100baseT/Half 100baseT/Full 

	                        1000baseT/Half 1000baseT/Full 

	Supported pause frame use: No

	Supports auto-negotiation: Yes

	Advertised link modes:  10baseT/Half 10baseT/Full 

	                        100baseT/Half 100baseT/Full 

	Advertised pause frame use: Symmetric Receive-only

	Advertised auto-negotiation: Yes

	Link partner advertised link modes:  10baseT/Half 10baseT/Full 

	                                     100baseT/Half 100baseT/Full 

	                                     1000baseT/Half 1000baseT/Full 

	Link partner advertised pause frame use: Symmetric Receive-only

	Link partner advertised auto-negotiation: Yes

	Speed: 100Mb/s

	Duplex: Full

	Port: MII

	PHYAD: 0

	Transceiver: internal

	Auto-negotiation: on

	Supports Wake-on: pumbg

	Wake-on: d

	Current message level: 0x00000033 (51)

			       drv probe ifdown ifup

	Link detected: yes

why is the advertised link not 1000? even though it is a supportedmode?

--edit--

one reboot later and the connection is lost, link deteced has been set back to no  :Sad: 

--edit--

connection seems to work at times

changing the cable has gigabit ethernet working agian

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## Syl20

 *Adel Ahmed wrote:*   

> why is the advertised link not 1000? even though it is a supportedmode?

 

Maybe because of an unappropriate cable ? You need at least a Cat. 5e cable.

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## Adel Ahmed

you're right there, replacing the cable fixes things

thanks

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