we met the situation of Asymmetric Routing and topology change like below
https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6000-series-switches/23563-143.html#anc7
customer running two 6509, but only one wan link outside, so Asymmetric Routing and many many topology change cause 6509-1 mac address table flushed and arp table on 6509-1 still there . and cause unicast flooding on 6509-1
under above link said:
Note: In MSFC IOS, there is an optimization that will trigger VLAN interfaces to repopulate their ARP tables when there is a TCN in the respective VLAN. This limits flooding in case of TCNs, as there will be an ARP broadcast and the host MAC address will be relearned as the hosts reply to ARP.
but when i checked 6509-1 mac-adress table and arp table ,found when mac-address table was flushed by many topology change, and arp entry was still there, after some time mac address entry appeared,cause many unicast flooding during this time.
I want to ask is this feature need to enable? or enable by default.
but why it doesn't work?
due to arp rate limit protection on 6509?
thank you
Tom
