Problem interconnecting MDS9124 and MDS9120

[snabulast]

Hello

We are trying to connect  2 SAN switches .  Details :

cisco MDS 9124 (1 Slot) Chassis

Model number is DS-C9124-K9-SUP

Cisco Nexus Operating System (NX-OS) Software

Software

  BIOS:      version 1.0.19

  loader:    version N/A

  kickstart: version 5.0(1a)

  system:    version 5.0(1a)

cisco MDS 9100

Model number is DS-C9120-K9-SUP

Cisco Storage Area Networking Operating System (SAN-OS) Software

Software

  BIOS:      version 1.1.0

  loader:    version 1.2(2)

  kickstart: version 3.3(5)

  system:    version 3.3(5)

We want to make the  9124 an expansion of the 9120.  Therefore we want to define 2 ports in each switch to mode E, and make an ISL link.

The problem : when we try to define the E port, we get an error :

SW_A(config-if)# switchport mode E

fc1/6: (error) mode E allowed only for interface fc1/5 in group fc1/5-8

We don't want to define port fc1/5  in mode E, because , if we do that port 6,7,8 become unusable.

Any suggestions ?

Thank you.

[dakester]

Hi,

The 9120 has a hardware limitation.

http://www.cisco.com/en/US/docs/storage/san_switches/mds9000/sw/rel_3_x/configuration/guides/cli_3_3/intf.html#wp1242298
In the Cisco MDS 9100 Series, the left most groups of ports outlined in white (4 ports in the 9120 switch and 8 ports in the 9140 switch) are full line rate like the 16-port switching module. The other ports (16 ports in the 9120 switch and 32 ports in the 9140 switch) are host-optimized like the 32-port switching module. Each group of 4 host-optimized ports have the same rules as for the 32-port switching module.

When configuring these host-optimized ports, the following port mode guidelines apply:
You can configure only the first port in each 4-port group (for example, the first port in ports 1-4, the fifth port in ports 5-8 and so on) as an E port. If the first port in the group is configured as an E port, the other three ports in each group (ports 2-4, 6-8 and so on) are not usable and remain shutdown.

Since the 9120 (Gen1) is attaching to the 9124 (Gen2), keep this in mind.
http://www.cisco.com/en/US/docs/switches/datacenter/mds9000/sw/5_0/release/notes/nxos/mds_nxos_rel_notes_501a.html#wp419251
When a Cisco or other vendor switch port is connected to a Generation 1 module port (ISL connection), the receive buffer-to-buffer credit of the port connected to a Generation 1 module port should not exceed 255.

On the 9124, you may have to configure the interface as...
switchport fcrxbbcredit 255

Regards,
David