Why not to keep PVID 1 as default ?

[Eddy Kvetny]

Hi,

On init the PortOrch explicitely removes all ports which are members in the default VLAN (usually VID 1) from it. Then I add some port as tagged to the existing VLAN group(s). No explicit PVID is configured in SONIC at the moment.

What is expected to happen to untagged packets that can come on this port (e.g. L2 control packets like LLDP, LACP, EAPOL ...) ? Definitely we don't want to drop them but deliver to SONIC. My question is related to the FDB learning event. Most of switches always keep VID 1 as default PVID. So, the FDB learning happens on this VID 1 while SONIC explicitely removed the membership from this VID on all ports. It might result in desync between switch and SONIC, VID 1 with partial data in the DB and end up in some band-aid solutions such as VID 1 fix

What was the motivation for removing all ports from the default VLAN ? Why don't we want SONIC to have the default VLAN ID (1) defined as PVID unless something else is defined as PVID (e.g. on addition of a port as tagged to a certain VLAN group)

Thanks in advance for clarifications

Regards, Eddy

[Prince Sunny]

The main reason is to bring up Sonic as a L3 switch by default in DC deployments. If not, there could be packet loops in network that can cause unexpected failure scenarios. This was the motivation. So if user wants such L2 configs and PVID, let it be explicitly configured, rather than defaults.

 

..Prince

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[Eddy Kvetny]

Thanks for the fast response Prince

So, for VLAN trunk (a port who joined VLAN groups as tagged only) all utagged traffic is expected to be dropped unless PVID is explicitely configured ?

[Prince Sunny]

Yes

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