We have a client with a two unit X450 stack with about 400 layer 3 VLAN interfaces and we are finding that the ARP Pending Entries queue increases to whatever the upper limit is set to. We are also seeing that an apparently random selection of hosts connected to the switches becomes occasionally becomes unreachable, which would make sense given that the switch is unable to resolve ARP for them.
This started being noticable at around 350 layer 3 VLAN but increasing the Pending Entries limit seemed to keep it in check for a while, although I guess that might have just lowered the number of complaints. Whatever limit is set, though, seems to always be reached in a few days
Does anyone know if there is some known limitation with the X450 or XOS 22.214.171.124 that can cause this behaviour? Can the issue perhaps be resolved by using a different firmware version? If so, what is recommended for the X450?
Any other ideas for mitigating this problem?
The output of 'show iparp" gives the following statistics:
Dynamic Entries : 347 Static Entries : 0
Pending Entries : 2048
In Request : 34990997 In Response : 590791
Out Request : 31413049 Out Response : 20684269
Failed Requests : 5137454
Proxy Answered : 2583974
Rx Error : 4 Dup IP Addr : a.b.c.177
Rejected Count : 485915 Rejected IP : 169.254.135.15
Rejected Port : 1:21 Rejected IF : CLIENT134
Max ARP entries : 8192 Max ARP pending entries : 2048
ARP address check: Enabled ARP refresh : Enabled
Timeout : 20 minutes ARP Sender-Mac Learning : Disabled