Thanks for the update. Was it really a broadcast storm? It sounds like it
was excessive retransmissions, which certainly could happen if static
routes were removed. Clients trying to reach servers across the AS400
(which presumably does routing) would just keep trying and trying. But the
frames weren't addressed to the broadcast address, I would guess? A
broadcast storm means excessive broadcasts. It's even worse than what you
describe! ;-)
Priscilla
At 08:58 AM 4/30/01, Sites, Bob wrote:
>Just wanted to update the list on this matter because I feel that it could
>very easily happen to anyone of you and it was very difficult to locate the
>problem. Got to blame this one on Big Blue hardware. Yes, the AS400 was the
>cause of all our problems here, once again. Apparently several days prior to
>this problem, the AS400 was upgraded and a rollover software called Visions
>was added. This is similar in function to HSRP. A third party software that
>allows rollover from one AS400 to another. Anyway, during the setup for the
>rollover testing it was recommended that some static routes in the AS400 be
>cleaned up and deleted. Way to go Visions! Our AS400 folks didn't know any
>better and just deleted static routes down from about a dozen to 4!!! Our
>symptoms were major broadcast storms of retransmissions. Got to keep a close
>eye on those big blue boys! Of course, as always, it was a "network" problem
>and the network team solved it!!! Is it at all possible that IBM could come
>up with a more worthless IP stack?
>
>Bob Sites, CCNA
>Winchester Medical Center
>
>
>Do you have a TACAC's, Syslog server, & or SNMP database server. Helps you
>find the who, what, where, & when things started. Sometimes you gotta dig
>backwards when the obvious just won't present itself. My guess is that you
>have a link down, a flapping interface, or had bounce on a link that the
>protocol wasn't configured to handle.
>
>Please keep us posted with your success or failures
>Phil
>
>Perhaps someone could steer me on this problem that I've been fighting for
>a day and half now. We are having a severe slowdown on our network and when
>looking at the IP traffic from just about anywhere to anywhere, about 1/3
>of the packets are being retransmitted? Sniffer error is "excessive
>retransmissions." Spent about 3 hours on the phone this morning with the
>TAC and didn't really get anywhere. It appears that we are having a
>broadcast storm of the retransmissions. Any insight into what direction
>to head would be greatly appreciated. Would like to isolate the problem by
>blades on the switches or routers, but being a hospital this is almost
>impossible. We have 2 core 6509's with duplicate sups and msfc's. Main
>router is a 7200.
>
>Bob Sites, CCNA
>Winchester Medical Center
>
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Priscilla Oppenheimer
http://www.priscilla.com
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