Dell Networking when LACP individual is triggered into Individual Port results in its associated Vlans MTU change to 1532 in 10.5.4.X releases
Summary: This article explains about LACP individual triggered causes LACP Individual Port change to 1532. As a result, LACP Individual member interface and any Vlan in the Port channel has its MTU lowered to 1532. This article is applicable only to 10.5.4.X releases. ...
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Instructions
NOTE: This article is applicable only to 10.5.4.X releases. We tested in 10.5.5.10 and 10.5.6.0, and the behavior was not seen.
Index
IntroductionHow MTU is impacted when LACP is triggered in 10.5.4.x releases.
Example
Case 1 When Port-channel is up. MTU of member interface and Vlan MTU is unchanged.
Case 2 When Port-channel and member interface is Down. MTU of member interface and Vlan MTU is unchanged.
Case 3 When Port-channel and member interface is up and LACP Individual is triggered. MTU of member interface and Vlans MTU Changes to 1532
Comparison between Impact of MTU on member interface and Vlan when LACP Individual is triggered.
Workaround
Introduction
What is LACP Individual?
LACP LAG members that do not receive LACP PDUs are set to an Inactive state. However, in certain deployments, LAG members that are in Inactive state must be isolated, so that they can be viewed as separate individual ports. Individual ports are not a part of the LAG. Normal network traffic flows through these individual ports. The objective of this feature is to make the individual ports available for normal traffic flow, even though they remain as inactive members of the parent LAG.
For example, consider Port-channel 1 has a member interface Eth 1/1/1. Lets do a comparison when member between Port-channel up and Port-channel down with LACP Individual triggered.
| When Port-channel is up | When Port-channel is Down and member port Eth 1/1 /1is up |
|---|---|
OS10# show port-channel summary
Flags: D - Down I - member up but inactive P - member up and active
U - Up (port-channel) F - Fallback Activated IND - LACP Individual
--------------------------------------------------------------------------------
Group Port-Channel Type Protocol Member Ports
--------------------------------------------------------------------------------
1 port-channel1 (U) Eth DYNAMIC 1/1/1(P) |
OS10# show port-channel summary
Flags: D - Down I - member up but inactive P - member up and active
U - Up (port-channel) F - Fallback Activated IND - LACP Individual
--------------------------------------------------------------------------------
Group Port-Channel Type Protocol Member Ports
--------------------------------------------------------------------------------
1 port-channel1 (D) Eth DYNAMIC 1/1/1(IND) |
OS10# show vlan
Codes: * - Default VLAN, M - Management VLAN, R - Remote Port Mirroring VLANs,
@ - Attached to Virtual Network, P - Primary, C - Community, I - Isolated,
S - VLAN-Stack VLAN
Q: A - Access (Untagged), T - Tagged
NUM Status Description Q Ports
* 1 Active A Eth1/1/2-1/1/56
A Po1
2 Active T Po1 |
OS10# show vlan
Codes: * - Default VLAN, M - Management VLAN, R - Remote Port Mirroring VLANs,
@ - Attached to Virtual Network, P - Primary, C - Community, I - Isolated,
S - VLAN-Stack VLAN
Q: A - Access (Untagged), T - Tagged
NUM Status Description Q Ports
* 1 Active A Eth1/1/1-1/1/56
A Po1
2 Active T Eth1/1/1
T Po1 |
When the LACP Individual is triggered, the Individual port Eth 1/1/1 becomes independent part of Vlans as shown in the above output(Highlighted). When Port-channel is up, its member port is part of Port-channel and hence we do not see it separately in show vlan output.
NOTE: The default MTU from 10.5.4.4 and above is 9216. On 10.5.4.3 and prior releases the default MTU was 1532.
How LACP Individual interface and associated Vlan MTU is impacted when LACP Individual is triggered in 10.5.4.x releases
When LACP Individual is triggered by a Port-channel down condition the following happens in 10.5.4.X releases,
-The LACP individual interface starts to forward the traffic. It acts as an independent port with no LACP and the same vlan configuration of the Port-channel.
-The Individual interface MTU is brought down to 1532 when LACP Individual is triggered on 10.5.4.X.
-This in turn brings down the MTU of all its associated Vlans of the Port-channel to 1532.
NOTE: Only Vlans allowed in the specific Port-channel which went down and LACP individual triggered, is impacted by this behavior in 10.5.4.x releases. MTU of other Vlan in switch will not change to 1532.
Let us explain the behavior in detail with an example.
Consider we have Port-channel 1 with Member port Eth 1/1/1. We have LACP Individual configured. We have default MTU 9216. Interfaces are left with the default MTU configuration.
OS10# show running-configuration interface port-channel 1
!
interface port-channel1
no shutdown
switchport mode trunk
switchport access vlan 1
switchport trunk allowed vlan 2
lacp individual |
OS10# show running-configuration interface ethernet 1/1/1 ! interface ethernet1/1/1 no shutdown channel-group 1 mode active no switchport |
OS10# show running-configuration interface vlan 1 interface vlan1 no shutdown OS10# show running-configuration interface vlan 2 interface vlan2 no shutdown |
OS10# show default mtu
Default MTU 9216 bytes |
Case 1 When Port-channel is up. MTU of member interface and Vlan MTU is unchanged.
Here Portchannel and member interface is UP. LACP Individual is not triggered. MTU of member interface and Vlan MTU is unchanged.
OS10# show port-channel summary
Flags: D - Down I - member up but inactive P - member up and active
U - Up (port-channel) F - Fallback Activated IND - LACP Individual
--------------------------------------------------------------------------------
Group Port-Channel Type Protocol Member Ports
--------------------------------------------------------------------------------
1 port-channel1 (U) Eth DYNAMIC 1/1/1(P) |
We can see the MTU of the member interface, and Vlan MTU is the same as Default MTU. (Output trimmed for brevity)
OS10# show default mtu
Default MTU 9216 bytes |
OS10# show interface port-channel 1
Port-channel 1 is up, line protocol is up
MTU 9216 bytes, IP MTU 9184 bytes |
OS10# show interface ethernet 1/1/1
Ethernet 1/1/1 is up, line protocol is up
MTU 9216 bytes, IP MTU 9184 bytes |
OS10# show interface vlan 1
Vlan 1 is up, line protocol is up
MTU 9216 bytes, IP MTU 9184 bytes |
OS10# show interface vlan 2
Vlan 2 is up, line protocol is up
MTU 9216 bytes, IP MTU 9184 bytes |
Case 2 When Portchannel and member interface is Down. LACP Individual is not triggered. MTU of member interface and Vlan MTU is unchanged.
Here Portchannel and member interface is Down. LACP Individual is not triggered. MTU of member interface and Vlan MTU is unchanged.
OS10# show port-channel summary Flags: D - Down I - member up but inactive P - member up and active U - Up (port-channel) F - Fallback Activated IND - LACP Individual -------------------------------------------------------------------------------- Group Port-Channel Type Protocol Member Ports -------------------------------------------------------------------------------- 1 port-channel1 (D) Eth DYNAMIC 1/1/1(D) |
We can see the MTU of the member interface, and Vlan MTU is the same as Default MTU. (Output trimmed for brevity)
OS10# show default mtu
Default MTU 9216 bytes |
OS10# show interface port-channel 1
Port-channel 1 is up, line protocol is down
MTU 9216 bytes, IP MTU 9184 bytes |
OS10# show interface ethernet 1/1/1
Ethernet 1/1/1 is up, line protocol is down
MTU 9216 bytes, IP MTU 9184 bytes |
OS10# show interface vlan 1
Vlan 1 is up, line protocol is down
MTU 9216 bytes, IP MTU 9184 bytes |
OS10# show interface vlan 2
Vlan 2 is up, line protocol is down
MTU 9216 bytes, IP MTU 9184 bytes |
Case 3 When Portchannel and member interface is up and LACP Individual is triggered. MTU of member interface and MTU Changes
Here the Port-channel is Down. Member interface Eth 1/1/1 is up. As a result LACP Individual is triggered. MTU of member interface and Vlan MTU is lowered to 1532.
OS10# show port-channel summary
Flags: D - Down I - member up but inactive P - member up and active
U - Up (port-channel) F - Fallback Activated IND - LACP Individual
--------------------------------------------------------------------------------
Group Port-Channel Type Protocol Member Ports
--------------------------------------------------------------------------------
1 port-channel1 (D) Eth DYNAMIC 1/1/1(IND)
|
We can see the MTU of member interface, and Vlan MTU has changed to 1532(highlighted in RED). The default MTU and Port-channel MTU is 9216. (Output trimmed for brevity)
OS10# show default mtu
Default MTU 9216 bytes |
OS10# show interface port-channel 1
Port-channel 1 is up, line protocol is down
MTU 9216 bytes, IP MTU 9184 bytes
|
OS10# show interface ethernet 1/1/1
Ethernet 1/1/1 is up, line protocol is up
MTU 1532 bytes, IP MTU 1500 bytes |
OS10# show interface vlan 1
Vlan 1 is up, line protocol is up
MTU 1532 bytes, IP MTU 1500 bytes |
OS10# show interface vlan 2
Vlan 2 is up, line protocol is up
MTU 1532 bytes, IP MTU 1500 bytes |
Comparison between Impact of MTU on member interface and Vlan when LACP Individual is triggered.
| Port-channel and Interface is Up | Port-channel and interface is down (LACP Individual not triggered) | Port-channel is down, and the member interface is up. LACP Individual is triggered | |
|---|---|---|---|
| Default MTU | 9216 | 9216 | 9216 |
| Port-channel MTU | 9216 | 9216 | 9216 |
| LACP Independent Interface MTU | 9216 | 9216 | 1532 |
| MTU of Vlan allowed in Port-channel | 9216 | 9216 | 1532 |
Workaround
As a workaround we can configure the MTU Manually on the Port-channel interface. VLAN memberships and MTU are inherited from the parent LAG to the individual member ports.
Sample Configuration
OS10# configure terminal OS10(config)# interface port-channel 1 OS10(conf-if-po-1)# mtu 9216 OS10(conf-if-po-1)# end |
After Manually configuring MTU in PortChannel, we can see the MTU in Interface and Vlans does not change after LACP individual is triggered.
OS10# show port-channel summary
Flags: D - Down I - member up but inactive P - member up and active
U - Up (port-channel) F - Fallback Activated IND - LACP Individual
--------------------------------------------------------------------------------
Group Port-Channel Type Protocol Member Ports
--------------------------------------------------------------------------------
1 port-channel1 (D) Eth DYNAMIC 1/1/1(IND)
|
We can see the MTU of the member interface, and Vlan MTU is the same as Default MTU. (Output trimmed for brevity)
OS10# show default mtu
Default MTU 9216 bytes |
OS10# show interface port-channel 1
Port-channel 1 is up, line protocol is down
MTU 9216 bytes, IP MTU 9184 bytes |
OS10# show interface ethernet 1/1/1
Ethernet 1/1/1 is up, line protocol is up
MTU 9216 bytes, IP MTU 9184 bytes |
OS10# show interface vlan 1
Vlan 1 is up, line protocol is up
MTU 9216 bytes, IP MTU 9184 bytes |
OS10# show interface vlan 2
Vlan 2 is up, line protocol is up
MTU 9216 bytes, IP MTU 9184 bytes |
Affected Products
PowerSwitch S4048-ON, PowerSwitch S4048T-ON, PowerSwitch S4112F-ON/S4112T-ON, PowerSwitch S4128F-ON/S4128T-ON, PowerSwitch S4148F-ON/S4148T-ON/S4148FE-ON, PowerSwitch S4148U-ON, PowerSwitch S5048F-ON, PowerSwitch S5148F-ON, PowerSwitch S5212F-ON
, PowerSwitch S5224F-ON, PowerSwitch S5232F-ON, PowerSwitch S5248F-ON, PowerSwitch S5296F-ON, PowerSwitch S5448F-ON, PowerSwitch Z9100-ON, PowerSwitch Z9264F-ON, PowerSwitch Z9332F-ON, PowerSwitch Z9432F-ON
...
Article Properties
Article Number: 000225833
Article Type: How To
Last Modified: 20 Jun 2024
Version: 4
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