Somewhat weird net behavior

[Milan Obuch]

Hi,
I am seeing something strange on couple of our routers. All are WRAP based on 
6.1-RELEASE-p6, easiest description is:

# ping <any-public-ip>
PING <any-public-ip>: 56 data bytes
ping: sendto: No buffer space available
ping: sendto: No buffer space available
^C
--- <any-public-ip> ping statistics ---
2 packets transmitted, 0 packets received, 100% packet loss
# ifconfig sis0 up
# ping <any-public-ip>
PING <any-public-ip>: 56 data bytes
64 bytes from <any-public-ip>: icmp_seq=0 ttl=64 time=2.310 ms
^C
--- <any-public-ip> ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 2.310/2.310/2.310/0.000 ms

I know this is really minimum information here, but I need just an idea what 
to look for. It is strange for me - is it some memory leak? How could it be 
cleared with simple ifconfig up? Did anyone seen something similar?

Regards,
Milan

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