Concept Guide

• For ports directly attached to the chassis you can have a maximum of 4 sessions per port pipe.
Refer to Port Numbering Convention for the exact port location on switch line cards.
Congure MTU Size on an Interface
Maximum Transmission Unit (MTU) is dened as the entire Ethernet packet (Ethernet header + FCS + payload).
The link MTU is the frame size of a packet, and the IP MTU size is used for IP fragmentation. If the system determines that the IP packet
must be fragmented as it leaves the interface, the system divides the packet into fragments no bigger than the size set in the ip mtu
command.
NOTE: Because dierent networking vendors dene MTU dierently, check their documentation when planning MTU sizes
across a network.
The following table lists the range for each transmission media.
Transmission
Media
MTU Range (in bytes)
Ethernet
The MTU range is from 594 to 9216, with a default of 1554.
The IP MTU automatically congures.
Using Ethernet Pause Frames for Flow Control
Ethernet Pause Frames allow for a temporary stop in data transmission. A situation may arise where a sending device may transmit data
faster than a destination device can accept it. The destination sends a PAUSE frame back to the source, stopping the sender’s
transmission for a period of time.
An Ethernet interface starts to send pause frames to a sending device when the transmission rate of ingress trac exceeds the egress
port speed. The interface stops sending pause frames when the ingress rate falls to less than or equal to egress port speed.
The globally assigned 48-bit Multicast address 01-80-C2-00-00-01 is used to send and receive pause frames. To allow full-duplex ow
control, stations implementing the pause operation instruct the MAC to enable reception of frames with destination address equal to this
multicast address.
The PAUSE frame is dened by IEEE 802.3x and uses MAC Control frames to carry the PAUSE commands. Ethernet pause frames are
supported on full duplex only.
If a port is over-subscribed, Ethernet Pause Frame ow control does not ensure no-loss behavior.
Restriction: Ethernet Pause Frame ow control is not supported if PFC is enabled on an interface.
Control how the system responds to and generates 802.3x pause frames on Ethernet interfaces. The default is rx o tx o. INTERFACE
mode. flowcontrol rx [off | on] tx [off | on] monitor session-ID
Where:
rx on: Processes the received ow control frames on this port.
rx off: Ignores the received ow control frames on this port.
tx on: Sends control frames from this port to the connected device when a higher rate of trac is received.
tx off: Flow control frames are not sent from this port to the connected device when a higher rate of trac is received.
Interfaces
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