S6700 some eth-trunk Member interface not forwarding any traffic
Issue Description
2*S6700 switches are stacked , and eth-trunk 2 was configured on it.
it was observed that some eth-trunk member interface are not forwarding anytraffic out.
TOPOLOGY : –
Alarm Information
From the display interface brief
there is no out traffic on port Xgig 1/0/1 and X gig 1/0/2
Handling Process
when we checked inbound interface we found that all the incoming traffic is coming on slot 0 switch only .
from the ports we can see xgig 0/0/11 to port xgig 0/0/14
Root Cause
when we observe diagram and traffic pattern its found all the traffic input coming on slot 0 means on 1 of the switches only .
In this case this behavior is normal because of feature called local preference , the switch will select the local chassis outgoing interface for sending the traffic
If active interfaces in the local Eth-Trunk have sufficient bandwidth to forward traffic on the local device, configure the Eth-Trunk to preferentially forward local traffic, which improves traffic forwarding efficiency and increases bandwidth use efficiency between stack devices.
If active interfaces in the local Eth-Trunk do not have sufficient bandwidth to forward traffic on the local device, configure the Eth-Trunk not to preferentially forward local interface traffic. Some traffic on the local device is forwarded through member interfaces of an Eth-Trunk on another device. This prevents packet loss.
Solution
In this case to utilise all port bandwidth , the solution is to disable the local-preference feature so that switch will select the another chassis outbound port also into consideration for forwarding the traffic
