[ale] SSH Cisco Networking Issue

[Paul Cartwright]

On Mon September 27 2010, Michael H. Warfield wrote:
> You MIGHT try "ping -M do -s 1500 host" and see if it breaks.  The "-M
> do" says do prohibit fragmentation (don't ask - I don't know why it's
> that way) and the -s 1500 sets the packet size.  Back it down till it
> works.  If it does, you have your smoking gun.  Still, I'm not sure I
> can guarantee the test.

so, I am an atnex.net customer, and I tried that with this line:
ping -M do -s 1460 atnex.net
PING atnex.net (208.65.89.2) 1460(1488) bytes of data.
1468 bytes from www.atnex.net (208.65.89.2): icmp_seq=1 ttl=124 time=51.4 ms
1468 bytes from autodiscover.atnex.net (208.65.89.2): icmp_seq=2 ttl=124 
time=50.5 ms
<SNIP>

--- atnex.net ping statistics ---
7 packets transmitted, 7 received, 0% packet loss, time 6022ms
rtt min/avg/max/mdev = 50.198/50.853/51.470/0.446 ms

with anything higher I got this:
>From paulandcilla.homelinux.org (192.168.10.2) icmp_seq=2 Frag needed and DF 
set (mtu = 1492)
^Cndcilla.homelinux.org (192.168.10.2) icmp_seq=2 Frag needed and DF set (mtu 
= 1492)

--- atnex.net ping statistics ---
1 packets transmitted, 0 received, +3908 errors, 100% packet loss, time 2459ms

so should I set my router to 1460? I had always used 1492, but I really can't 
remember why!

-- 
Paul Cartwright
Registered Linux user # 367800
Registered Ubuntu User #12459
http://usdebtclock.org/