CISCO 4503 not able to connect to 3COM 4900 at physical layer.

[renzil]

Hi,

I hve at the core a CISCO 4503 and need to connect various 3COM 3300/4400/4900 access switches thru fibre. The problem is tht the cisco core 4503 switch fails to recgonise only the 4900 3com switches ie the link status shows down. The fibre multimode link is tested and OK.The modules on both the switches ie 1000baseSX are also tested and ok.

The Cisco switch has a 6port gbic with 1000baseSX moules and the 3COM 4900 has a 4-port 1000baseSX module.

Thanks

Renzil

[jhalldn]

Hi Renzil!

Heres some ideas to think of!

Are you trying to configure the links as VLAN trunks?

Are connecting them with redundancy links?

How long are the fiber link (SX<500m)?

Is the port reporting error disabled state or loopback detected?

Try to configure:

# Both boxes hard with speed (1000) and duplex (full)(speed is not changeble with GE GBICs). Maybe som probs with negoating duplex.

# Use "udld aggressive" command on fiber links. Just so you dont have unidirectional problems.

# Try to diable spanning-tree on links "spanning-tree portfast". Make sure you dont have connected them in redundancy design. Maybe there can be som prblem with spanning-tree between 3COM/Cisco. Mono verses Per VLAN spanning-tree, root and secondary bridges.

# Try to disable keepalives on switchport, "no keepalive". Maybe the boxes cant understand each others hellos.

# Try to set "switchport access vlan x". Just to make sure it aint VLAN DOT1Q mapping.

# Last = switch the fibers TX RX (i just have to do this ;-) ).

[jhalldn]

I forgot something:

If your box or 3COM have inline power, you maybe have to disable that feature.

[haider.rizwan]

Hello,

Reference to above observations, which one worked ? I have same problem. please reply.

Bundle of thanks