Performance: Neighbour table overflow

Rajasekhar Inguva (irajasek@in.ibm.com)
Wed, 16 Jan 2002 11:43:46 +0530


Hi All,
I have observed that when the ARP cache is full , any further networking
apps fail with error "Neighbour table overflow" until a timer expires and
the cache is cleared. Below is a detailed re-creation scenario....

1) Set /proc/sys/net/ipv4/neigh/default/gc_thresh1,2,3 to values 2
2) ping one_neighbour ( arp cache now has this entry )
3) ping another_neighbour ( arp cache has now 2 entries )
4) ping third_neighbour

Neighbour table overflow
Ping: No buffer space available

Until the timer expires and the arp cache gets cleared , no further network
connections succeed.

IMHO, in situations wherein stale entries do exist in the cache and the
cache is full, then one should not wait for a timer expiry but remove a few
entries asap.

I get a feeling it might violate some rfc's , but i am not really sure....

Any feedback ?

Regards,

Raj

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