Flow-control recommendation

[BorislavPenchev0962]

Hi,

may you advise on Cisco Flow-control best practice for Nexus 55xx and Catalyst 65xx connection.we have seen some difference in flow-control configuration of Switch interfaces and not sure if this is ok ?

2 x Nexus 5596UP (L2 only) and Cisco Catalyst 6504(Layer 3) core with 10G int to the 5596UPs

Cisco Catalyst 6504:
show interface po30
Port-channel30 is up, line protocol is up (connected)
  Hardware is EtherChannel, address is 1111.1111.0000 (bia 1111.1111.0000)
  MTU 1500 bytes, BW 20000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 9/255, rxload 9/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  1., loopback not set
  Keepalive set (10 sec)
  Full-duplex, 10Gb/s, media type is unknown
  input flow-control is on, output flow-control is off
  Members in this channel: Te1/3 Te1/2
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output never, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/483804/353151 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)

Cisco Nexus 5596UP:
show interface po30
port-channel30 is up
 vPC Status: Up, vPC number: 40
  Hardware: Port-Channel, address: 1111.1111.990e (bia 1111.1111.990e)
  MTU 1500 bytes, BW 10000000 Kbit,, BW 10000000 Kbit, DLY 10 usec
  reliability 255/255, txload 10/255, rxload 7/255
  Encapsulation ARPA, medium is broadcast
  Port mode is trunk
  full-duplex, 10 Gb/s
  Input flow-control is off, output flow-control is off
  Switchport monitor is off
  EtherType is 0x8100
  Members in this channel: Eth1/3

Regards

Boris

[balaji.bandi]

As per the Cisco docementation (depends on your use case)

You use the flowcontrol interface configuration command to set the interface's ability to receive pause frames to on, off, or desired. The default state is off.

When set to desired, an interface can operate with an attached device that is required to send flow-control packets or with an attached device that is not required to but can send flow-control packets.

These rules apply to flow control settings on the device:

receive on (or desired The port cannot send pause frames but can operate with an attached device that is required to or can send pause frames; the port can receive pause frames.

receive off: Flow control does not operate in either direction. In case of congestion, no indication is given to the link partner, and no pause frames are sent or received by either device.

Command or Action	Purpose
Step 1	switch# configure terminal	Enters global configuration mode.
Step 2	switch(config)# interface type slot/port	Specifies the interface to be changed.
Step 3	switch(config-if)# flowcontrol [receive {on | off}] [transmit {on | off}]	Enables LLC for the selected interface. Set receive and/or transmit on or off.
Step 4	switch(config-if)# no flowcontrol [receive {on | off}] [transmit {on | off}]	(Optional) Disables LLC for the selected interface.

[00uwebuq2cv2rh8M55d6]

Cisco control best practise for Nexus 55xx for catalist 65xx connection. Input flow control is off output flow control is off Switchpory monitor is off EtherType is 0x8100 members.

[Joseph W. Doherty · Accepted solution]

I would recommend against using "standard" Ethernet flow control, unless you have a really good reason for using it, and you understand all its implications.

If your issue is interface drops, you're probably better managing congestion with QoS and/or buffer tuning.

If your equipment support a Data Center Ethernet variant, which also supports Priority-Based Flow Control: IEEE 802.1Qbb, that might be used.

(NB: Don't know off-hand, but if a Data Center Ethernet variant is supported, that's more likely on a Nexus vs. a Catalyst.)

Some more (brief) info: https://www.cisco.com/c/dam/en/us/solutions/collateral/data-center-virtualization/ieee-802-1-data-center-bridging/at_a_glance_c45-460907.pdf

[BorislavPenchev0962]

so following setup should be ok ?

Catalyst Port Te1/1 is connected with Nexus 5k Port Eth1/5.

Catalyst 6k
#sh int flowcontrol module 1
Port          Send FlowControl  Receive FlowControl  RxPause TxPause
              admin    oper     admin    oper
-----------   -------- -------- -------- --------    ------- -------
Te1/1         off      off      on       on          0       0
Te1/2         off      off      on       on          0       0

Nexus 5k:
# sh int flowcontrol module 1
--------------------------------------------------------------------------------
Port         Send FlowControl  Receive FlowControl  RxPause   TxPause
             admin    oper     admin    oper
--------------------------------------------------------------------------------
Eth1/5       off      off      off      off         0                 0