Users Guide

Congure MTU Size on an Interface
In Dell Networking OS, 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, Dell Networking OS 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
594-12000 = link MTU
576-9234 = IP MTU
Link Bundle Monitoring
Monitoring linked LAG bundles allows trac distribution amounts in a link to be monitored for unfair distribution at any given time. A
threshold of 60% is dened as an acceptable amount of trac on a member link. Links are monitored in 15-second intervals for three
consecutive instances. Any deviation within that time sends Syslog and an alarm event generates. When the deviation clears,
another Syslog sends and a clear alarm event generates.
The link bundle utilization is calculated as the total bandwidth of all links divided by the total bytes-per-second of all links. If you
enable monitoring, the utilization calculation is performed when the utilization of the link-bundle (not a link within a bundle) exceeds
60%.
To enable and view link bundle monitoring, use the following commands.
• Enable link bundle monitoring.
ecmp-group
• View all LAG link bundles being monitored.
show running-config ecmp-group
Using Ethernet Pause Frames for Flow Control
Ethernet pause frames and threshold settings are supported on the Dell Networking OS.
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.
Interfaces
393