[j-nsp] DDOS/Poor Ping on New M5

[Blaz Zupan]

> One of the M5's, lets call it router A (Brand new, with 600-512 RE) is
> pinging badly and ssh sessions are slow on all interfaces apart from fxp0.
> It's still passing traffic, however, there is a bad ping time here and there
> and snmp time outs also.

By any chance, does the traffic on this M5 pass through a gigabit ethernet
link? We've seen something like this, with about 150 Mbps passing through a
gigabit ethernet link on a M5 and the ping was around 1500 ms. We replaced
everything including the card itself, the whole box and the software, but
nothing really fixed the trouble.

After much headbanging, I found out that ethernet flow control between the M5
and the Cisco 3550 switch it was connected to was causing the trouble. Turning
off flow control fixed the problem and pings were back to below 1 ms even when
150 Mbps was passing through the link.