[e-nsp] ARP Pending Entries queue being maxed out

[Warwick Duncan]

Hello all

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.

Does anyone know if there is some known limitation with the X450 or XOS
12.4.1.7 that can cause this behaviour? Can the issue be resolved by
using a different firmware version?

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
==========================================================

Regards
Warwick

-- 
Warwick Duncan
Frogfoot Networks ISP
http://www.frogfoot.com/
+27.21.448.7225