2910al - Flowcontrol not active on trunks

[ZF]

Hi,

I've build a network setup to use as iscsi backbone. It consists of four switches which are connected as a ring:

Switch 1 == Switch 3

||                                ||

Switch 2 == Switch 4

The switches are placed at two sites. Switch 1 & 2 are at site A, Switch 3 & 4 at site B. Earch switch is connected to two of the others by 2x 1gbit trunks. As media, copper cables are used for trunks which connect switches in the same site, SX gbics + fibers are used for trunks which connect both sites. Multiple spanning tree is used to disable redundant paths.

Flow control is enable on all ports which are used for the trunks, but only the sx fiber optical ports use it...

switch4# sh interfaces brief 
  Status and Counters - Port Status
 
                    | Intrusion                           MDI  Flow Bcast
  Port    Type      | Alert     Enabled Status Mode       Mode Ctrl Limit
  ------- --------- + --------- ------- ------ ---------- ---- ---- -----
  1       100/1000T | No        Yes     Up     1000FDx    MDI  on   0
  2       100/1000T | No        Yes     Up     1000FDx    MDIX on   0
  3       100/1000T | No        Yes     Down   1000FDx    Auto off  0
  4       100/1000T | No        Yes     Down   1000FDx    Auto off  0
  5       100/1000T | No        Yes     Down   1000FDx    Auto off  0
  6       100/1000T | No        Yes     Down   1000FDx    Auto off  0
  7       100/1000T | No        Yes     Down   1000FDx    Auto off  0
  8       100/1000T | No        Yes     Down   1000FDx    Auto off  0
  9       100/1000T | No        Yes     Down   1000FDx    Auto off  0
  10      100/1000T | No        Yes     Down   1000FDx    MDI  off  0
  11      100/1000T | No        Yes     Down   1000FDx    Auto off  0
  12      100/1000T | No        Yes     Down   1000FDx    Auto off  0
  13      100/1000T | No        Yes     Up     1000FDx    MDIX off  0
  14      100/1000T | No        Yes     Up     1000FDx    MDI  off  0
  15      100/1000T | No        Yes     Down   1000FDx    Auto off  0
  16      100/1000T | No        Yes     Down   1000FDx    Auto off  0
  17      100/1000T | No        Yes     Down   1000FDx    Auto off  0
  18      100/1000T | No        Yes     Down   1000FDx    Auto off  0
  19      100/1000T | No        Yes     Down   1000FDx    Auto off  0
  20      100/1000T | No        Yes     Up     100FDx     MDI  off  0
  21-Trk1 100/1000T | No        Yes     Up     1000FDx    MDIX off  0
  22-Trk1 100/1000T | No        Yes     Up     1000FDx    MDIX off  0
  23-Trk2 1000SX    | No        Yes     Up     1000FDx         on   0
  24-Trk2 1000SX    | No        Yes     Up     1000FDx         on   0
 
 
switch4# sh interfaces config
 
 Port Settings
 
  Port    Type      | Enabled Mode         Flow Ctrl MDI
  ------- --------- + ------- ------------ --------- ----
  1       100/1000T | Yes     Auto         Enable    Auto
  2       100/1000T | Yes     Auto         Enable    Auto
  3       100/1000T | Yes     Auto         Disable   Auto
  4       100/1000T | Yes     Auto         Disable   Auto
  5       100/1000T | Yes     Auto         Disable   Auto
  6       100/1000T | Yes     Auto         Disable   Auto
  7       100/1000T | Yes     Auto         Disable   Auto
  8       100/1000T | Yes     Auto         Disable   Auto
  9       100/1000T | Yes     Auto         Disable   Auto
  10      100/1000T | Yes     Auto         Disable   Auto
  11      100/1000T | Yes     Auto         Disable   Auto
  12      100/1000T | Yes     Auto         Disable   Auto
  13      100/1000T | Yes     Auto         Disable   Auto
  14      100/1000T | Yes     Auto         Disable   Auto
  15      100/1000T | Yes     Auto         Disable   Auto
  16      100/1000T | Yes     Auto         Disable   Auto
  17      100/1000T | Yes     Auto         Disable   Auto
  18      100/1000T | Yes     Auto         Disable   Auto
  19      100/1000T | Yes     Auto         Disable   Auto
  20      100/1000T | Yes     Auto         Disable   Auto
  21-Trk1 100/1000T | Yes     Auto         Enable    Auto
  22-Trk1 100/1000T | Yes     Auto         Enable    Auto
  23-Trk2 1000SX    | Yes     Auto         Enable    0
  24-Trk2 1000SX    | Yes     Auto         Enable    0

Firmware W.14.49 is used.

Does anyone know why the switche don't use flow controll on the copper links?

greetings ZF