Port channel conf mismatch

[Rishav Garg]

Hi All,

In this scenario, On port channel we executed spanning-tree port type network but on members of same PO10. There is diff command

spanning-tree port type normal. In our env. it's running fine. But we are running static port-channel not LACP.

Will in future it could be any issue for this mismatch ?

interface port-channel10
  description vPC peer-link
  switchport mode trunk
  switchport trunk native vlan 99
  spanning-tree port type network
  vpc peer-link

interface Ethernet1/31
  switchport mode trunk
  switchport trunk native vlan 99
  spanning-tree port type normal
  channel-group 10

interface Ethernet1/32
  switchport mode trunk
  switchport trunk native vlan 99
  spanning-tree port type normal
  channel-group 10

[Bilal Nawaz]

Hello,

I think you should be OK for now, though I would advise to keep physical interfaces same as the port-channel.

In this scenario we have a port-channel with type network. This means that network ports are connected to only switches or bridges. Bridge assurance is enabled on network ports.

The physical ports with type normal, can be connected to either hosts, switches or bridges. Acts as normal spanning-tree port.

They both cater for the same, in that it connects to another switch, but if you have opportunity out of hours to make a change, then make them the same.

Bilal

[Rishav Garg]

Thanks for your Reply.

I know the diff. between Network vs Normal ports.

But i want to know currently  which type is active in my scenario either PO10 or interface level ? ( Network or normal)

What would be consequences in future if something go down?

[Bilal Nawaz]

What difference does spanning-tree type make if you have a switch connected to the other side?

Ans. No difference. They both do the same in this scenario.

If one of the links goes down, it behaves as a normal stp port. I and am sure others will/would strongly advise that you change the config when you can to make both port-channel interface and physical interface the same.

[Rishav Garg]

I got you.

Thanks for your answer.

But here one more doubt. Actually i read both port-channel interface and physical interface the same config as you said in above post.

But my question here in what case or what config difference let the port channel down. if conf not the same on both level.Because in my case spanning type is mismatched but still portchannel and interfaces are UP.

like eg if u configure speed on Po is 1000 and on interface is 100. Then portchannel never come UP. there will be a speed mismatch.

Is there any list of config. through which both will go down means portchannel and interface ?

[Bilal Nawaz]

Good question. I don't know is my answer, I haven't seen a full list of commands which would cause the interface / port-channel to not come up in bundled state / vice versa a list for differences which would allow a port to come up in a bundle state.

The general consensus has always been to keep the config same.

[Rishav Garg]

Thanks for your answers.

i read LACP will always match configuration. between different members or interfaces  NOT Between Portchannel and its member. Kindly help here. Does it true?

Regards

Rishav

[Bilal Nawaz]

Rishav, with mode set to ON, there is no negotiation of the port-channel, with LACP there is, negotiation with switch A to switch B. When port channel interfaces are configured improperly with LACP, they are disabled automatically to avoid network loops and other problems. To avoid configuration problems please observe these guidelines and restrictions:

•Every port added to a port channel must be configured identically. No individual differences in configuration are allowed. 

•Bundled ports can be configured on different line cards in a chassis. 

•Maximum Transmission Unit (MTU) must be configured only on port channel interfaces and this MTU is propagated to the bundled ports. 

•Quality of Service (QoS) and Committed Access Rate (CAR) are applied at the port level. Access control lists (ACLs) are applied on port channels. 

•MAC configuration is only allowed on port channels. 

•MPLS IP should be enabled on bundled ports using the mpls ip command. 

•You should apply Unicast Reverse Path Forwarding (uRPF) on the port channel interface using the ip verify unicast reverse-path command in interface configuration mode. 

•The Cisco Discovery Protocol (CDP) should be enabled on the port channel interface using the cdp enable command in interface configuration mode. 

•Enable all LAN ports in a port channel. If you shut down a LAN port in a port channel, it is treated as a link failure and its traffic is transferred to one of the remaining ports in the port channel. 

•To create a port channel interface, use the interface port-channel command in global configuration command. 

•When a Gigabit Ethernet interface has an IP address assigned, you must disable that IP address before adding the interface to the port channel. To disable an existing IP address, use the no ip address command in interface configuration mode. 

•The hold queue in command is only valid on port channel interfaces. The hold queue out command is only valid on bundled ports.

[Rishav Garg]

I also Got the answer.

Kindly follow this link. Some Writings here

Compatibility Requirements

When you add an interface to a channel group, the software checks certain interface attributes to ensure that the interface is compatible with the channel group. For example, you cannot add a Layer 3 interface to a Layer 2 channel group. The Cisco NX-OS software also checks a number of operational attributes for an interface before allowing that interface to participate in the port-channel aggregation.

The compatibility check includes the following operational attributes:

• Network layer
• (Link) speed capability
• Speed configuration
• Duplex capability
• Duplex configuration
• Port mode
• Access VLAN
• Trunk native VLAN
• Tagged or untagged
• Allowed VLAN list
• MTU size
• SPAN—cannot be a SPAN source or a destination port
• Layer 3 ports—cannot have subinterfaces
• Storm control
• Flow-control capability
• Flow-control configuration

Use the show port-channel compatibility-parameters command to see the full list of compatibility checks that the Cisco NX-OS uses.

You can only add interfaces configured with the channel mode set to on to static port channels, and you can only add interfaces configured with the channel mode as active or passive to port channels that are running LACP. You can configure these attributes on an individual member port. If you configure a member port with an incompatible attribute, the software suspends that port in the port channel.

Alternatively, you can force ports with incompatible parameters to join the port channel if the following parameters are the same:

• (Link) speed capability
• Speed configuration
• Duplex capability
• Duplex configuration
• Flow-control capability
• Flow-control configuration

When the interface joins a port channel, some of its individual parameters are removed and replaced with the values on the port channel as follows:

• Bandwidth
• Delay
• Extended Authentication Protocol over UDP
• VRF
• IP address (v4 and v6)
• MAC address
• Spanning Tree Protocol
• NAC
• Service policy
• Access control lists (ACLs)

Many interface parameters remain unaffected when the interface joins or leaves a port channel as follows:

• Beacon
• Description
• CDP
• LACP port priority
• Debounce
• UDLD
• MDIX
• Rate mode
• Shutdown
• SNMP trap

If you configure subinterfaces for the port-channel interface and remove a member port from the port channel, the configuration of the port-channel subinterface does not propagate to the member ports.

[Bilal Nawaz]

Good find Rishav :)

[Rishav Garg]

So in my scenario. Spanning tree command is mismatched.

But unfortunately Spanning tree is not an attribute to match between portchannel and its memeber interface.

That's why its running fine without issue.

That's is the correct answer.

Anyway thanks for your great help here.

[Bilal Nawaz]

One thing I found interesting - and I will quote here:

When the interface joins a port channel, some of its individual parameters are removed and replaced with the values on the port channel as follows

Spanning Tree Protocol

If you had spanning-tree port type edge then I suspect your theory will not apply. It is an attribute that must and should be the same in this case, because they we would have completely different behaviours.

[Rishav Garg]

Actually it applies.

run command : Show port-channel compatibility parameters

Under this it's not neccessary to match spanning tree protocol. when you add new interface into port-channel.

[Rishav Garg]

In my case somebody had forcefully change the behavoiur under interface.

Spanning tree port type normal.

But on portchannel: it's Spanning tree port type network.

It means when you add new interface to port channel with whatever type of spanning tree protocol. it resets to whatever Portchannel has. 

Im my case after that somebody has changed it  forcefully.

[Bilal Nawaz]

Hi Rishav, you are not understanding what I am trying to explain.

If you had spanning-tree port type edge, this is different to how network will operate, the characteristics do not match (one is expecting BPDU's [network], the other isn't [edge]), I do not know what the effect would be, but my guess is that they would not function.