LACP system Priority 0 in IOS XR

[parthiban chinnaya]

                 Why does Cisco devices running IOS XR doesnt form LACP when it receives system Prioirty 0 from peer switch.

                 I have checked with all other cisco IOS devices where it works fine.

                 Is there any specific reason in IOS XR to not allow system priority 0? 

[xthuijs]

System Priority = 0  is a special value.

In the spec of 802.3ad, while there is no EXPLICIT section that states
that 0 is an unacceptable value, there are sections where it says that
zero means ineligibility or absent/not present or disable.

What is explicitly mentioned that the system ID which is composed of mac
and priority cannot be all zero. So the prio >0 in XR (and IOS based switches btw)
will allow for accommodation of that clause.

Many OS's do not allow for a manual configuration of zero, but some (eg extreme) send it by default.

In short, a system priority of zero should not be used in general with lacp.

regards

xander