Service Manual

• All members must have the same link MTU value and the same IP MTU value.
• The port channel link MTU and IP MTU must be less than or equal to the link MTU and IP MTU values congured on the channel
members.
For example, if the members have a link MTU of 2100 and an IP MTU 2000, the port channel’s MTU values cannot be higher than
2100 for link MTU or 2000 bytes for IP MTU.
VLANs:
• All members of a VLAN must have the same IP MTU value.
• Members can have dierent Link MTU values. Tagged members must have a link MTU 4–bytes higher than untagged members
to account for the packet tag.
• The VLAN link MTU and IP MTU must be less than or equal to the link MTU and IP MTU values congured on the VLAN
members.
For example, the VLAN contains tagged members with Link MTU of 1522 and IP MTU of 1500 and untagged members with Link
MTU of 1518 and IP MTU of 1500. The VLAN’s Link MTU cannot be higher than 1518 bytes and its IP MTU cannot be higher than
1500 bytes.
Port-Pipes
A port pipe is a Dell Networking-specic term for the hardware path that packets follow through a system.
Port pipes travel through a collection of circuits (ASICs) built into line cards and RPMs on which various processing events for the
packets occur. One or two port pipes process trac for a given set of physical interfaces or a port-set.
Auto-Negotiation on Ethernet Interfaces
By default, auto-negotiation of speed and duplex mode is enabled on 10/100/1000 Base-T Ethernet interfaces. Only 10GE interfaces
do not support auto-negotiation.
When using 10GE interfaces, verify that the settings on the connecting devices are set to no auto-negotiation.
NOTE: When you use a copper SFP2 module with catalog number GP-SFP2-1T in the S25P model, you can manually set
its speed with the speed command. When the speed is set to 10Mbps or 100Mbps, you can execute the duplex
command.
The local interface and the directly connected remote interface must have the same setting, and auto-negotiation is the easiest way
to accomplish that, as long as the remote interface is capable of auto-negotiation.
NOTE: As a best practice, Dell Networking recommends keeping auto-negotiation enabled. Only disable auto-negotiation
on switch ports that attach to devices not capable of supporting negotiation or where connectivity issues arise from
interoperability issues.
For 10/100/1000 Ethernet interfaces, the negotiation auto command is tied to the speed command. Auto-negotiation is
always enabled when the
speed command is set to 1000 or auto.
Setting the Speed and Duplex Mode of Ethernet Interfaces
To discover whether the remote and local interface requires manual speed synchronization, and to manually synchronize them if
necessary, use the following command sequence.
1. Determine the local interface status. Refer to the following example.
EXEC Privilege mode
show interfaces [interface | stack—unit stack-unit-number] status
2. Determine the remote interface status.
EXEC mode or EXEC Privilege mode
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Interfaces