I've got a SG350X pair of switches connected to a Linux host. The LACP comes up and works fine.
gi1/0/1 and gi2/0/1 are in po1.
On Linux this is a 802.3ad bond0.
When I do "ifdown bond0" on Linux, I see these messages on the switch:
%STP-W-PORTSTATUS: Po1: STP status Forwarding
%LINK-I-Up: Po1
%TRUNK-I-PORTADDED: Port gi1/0/1 added to Po1
%LINK-W-Down: Po1
%TRUNK-W-PORTREMOVED: Port gi2/0/1 removed from Po1
%TRUNK-W-PORTREMOVED: Port gi1/0/1 removed from Po1
The problem appears to be that when I do "ifdown bond0", this doesn't actually shutdown the network interfaces physically, only logically. The same holds true if I do "ifconfig bond0 down" or "ip link set down bond0". While "bond0" and the member interfaces are down on Linux, "ethtool" shows that the links are actually up.
What appears to happen next is that because Cisco sees the physical lines (gi1/0/1 and gi2/0/1) as up, it does a "fallback" to "etherchannel" and brings po1 back up. I suspect this is the "auto" part of "channel-group 1 mode auto".
To work around Linux brain deadness (of not , is it possible to tell a SG350X to require LACP on a port channel? That is, if there is no LACP activity on a channel-group, don't bring it up. I suppose I want "channel-group 1 mode lacp".
Are there any secret settings or modes that can be used to tell the switch that a port-channel is to be LACP and LACP only? I would be happy to make all port-channel configurations on the SG350X behave like that.
