Re: Can someone explain this?

[DrFranken <midrange@xxxxxxxxxxxx>]

First of you should certainly have the CMNRCYLMT on your ETHERNET lines 
set to (1 0) to allow infinite retries.  ALL Y'ALL should be doing this 
in fact.

Well I don't think it was ARP on the i unless you use different IP 
Addresses for the HTTP servers than for Telnet. There is a one to one 
relationship between ARP entries and IP Addresses so you can't mess up 
the HTTP ARP entry and not the TELNET ARP entry as they would be the same.

In addition to that if you think about it, the ARP entries ON the i 
would be for itself but also for anything it's talking to. Neither the i 
nor the servers or clients it was talking to would have gotten a new ARP 
entry.  Only the switches changed. So lets look at the switches.

Switches have ARP tables too, in fact theirs are VERY important. When 
you pulled out the cable and moved it to the new switch it's not the ARP 
table on the i that had a problem, it's entries were still correct. The 
switches in the network however may very well have though the i was 
still where it was before - on the old switch. Hence traffic to it might 
still have been directed there and that switch, no longer able to 
communicate with it, simply dropped the packets. So the correct solution 
was to clear the ARP entries on the switches.

Depending on the switch brand you can clear those tables from command 
lines. You can always reboot them (not a pretty option.)   IPLing the i 
accomplished the task in a rather brute force way because when it came 
back up it advertised itself on the network as well as allowing for 
sufficient time to pass for the switches ARP data to age out.

So why could you connect with some things and not others? Very possibly 
because of the path to the system. Some switches had correct entries and 
others did not. Anything going through the old switch likely was getting 
stuck while traffic that made it to the new switch was likely OK.

But then I'm guessing a lot too. :-)

 - Larry "DrFranken" Bolhuis


On 4/14/2011 8:43 AM, Don Cavaiani wrote:
> Last night we put in all new switches, and quickly replugged the IBM i
> Ethernet cable, and the system went on running, telnet for sure.
>
> However, the http servers no longer connected.  This morning I
> re-started all the HTTP servers, but we were still unable to connect.
>
> I then did an IPL which brought everything back up.