Help, 3550 refuse to connect with 2950, but 2960 works well.

[StranavskyR]

We have a core switch Catalyst 3550-24-PWR

Connected are 2 Catalyst 2960 PoE-24 and one Catalyst 2950-24

3550 together 2960 works well

2960 together 2950 works well

3550 connected with 2950 refuse to establish connection. Port goes down immediately.

Example

3550 Fe0/19+Fe0/20 -> 2960 G0/1+G0/2 status OK

3550 Fe0/21+Fe0/22 -> 2960 G0/1+G0/2 status OK

2960 Fe0/12 -> 2950 Fe0/24 status OK

3550 Fe0/8 -> 2950 Fe0/24 status down

Anyone have an idea what should cause this behavior? I'm hopeless.

All the ports between switches are configured as Trunk (VLAN ALL)

[John Blakley]

Have you hardcoded both sides for speed/duplex?

Sent from Cisco Technical Support iPhone App

[StranavskyR]

Nope, as all ports are 10/100, but I will check and let you know.

Thanks

[Reza Sharifi · Accepted solution]

Have you tried a cross over cable between the 3550 and 2950?

[StranavskyR]

I don't, cause 2960 and 2950 works together on straight cable. I can try of course.

[glen.grant]

  Reza is correct , the 2960's have auto mdix capability so it doesn't matter if a crossover or straight thru is used as long as the port is set as auto.  Neither the 3550 or the 2950 have this capability so the cable "must" be a crossover to come active. 

[John Blakley]

Roman,

Reza and Glen are correct, and it didn't hit me that you weren't getting a physical connection at all. Use a crossover cable and you should be set.

HTH,

John

[StranavskyR]

Guys,

thanks for your suggestions, I will try the cross cable ASAP I will find some in the box.

Strange is, when I execute "reload" the switch is connected for a few seconds after soft restart, or at least the led is green. That's why I did suspect some feature on 3550.

btw, so far I remember, the 2950 was always connected to router directly, so was 3550 as well. This problem start after upgrade to 2950 to 2960.

Once tested, I will confirm if it works.

Thanks again to all of You.

Regards
Roman

[StranavskyR]

I can confirm CROSS OVER cable solved the issue.

Thank's to all of you once again.

Regards

Roman