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ICMP source quench problem

ICMP source quench problem

ICMP source quench problem


I struggle for some time now with a strange problem. I have a part of a network with following conenctions:

Core Switch--1Gb--C4948--100Mb--Avaya P580--100Mb--Server

Whenever I ping Server(HP-UX) from anything but the first Avaya depicted above I get ICMP Source Quench back in a reply. I guess it means that packets are sent to fast and the Server`s buffer cannot  serve them. But what might be the reason it does not appear when I try it from Avaya? Am I correct the problem lies on the Server side (too small buffer is set)? Had anyone similar problem?

RE: ICMP source quench problem

Is SAM reporting any errors, or GSP in the HP-UX box? Is this an HP-9000 or HP-3000? Actually, it seems the problem could lie in the Avaya device...are there VLANs set up in the Avaya? Can you look at debug messages in the Avaya?


RE: ICMP source quench problem

Unfortuantely I am not able to answer question regarding HP-UX (I do not manage them). Speaking about Avaya, there are some VLANs, I will look up debug msgs. and will post it here, but why do you think it is Avaya actually Avaya seems to be the one not doing any problems. Moreover I have some other HP-UX connected to this Avaya on the other port giving no errors.

I wonder why does the buffer fills up when pinging from anything but Avaya. I will also try to ping it from any other Avaya (they have similar configuration) being in the other part of the network. I will do more checkup on Monday but will be grateful for any suggestions meanwhile.

RE: ICMP source quench problem

I am suggesting the Avaya because from the outgoing interface, you see no problems, but anything before the Avaya (I.E., the incoming interface) is when you get the source quench problems.
If the Avaya is connected to the Cisco 4948, why not bypass the Avaya altogether and configure the VLANs in the C4948?
Anyway, you can try an extended ping from the 4948, and enter advanced options, and set the DF bit to 1, which will let you know if it is an MTU issue. Also, you can set the ICMP packet size small, and gradually make it bigger, to see when the source-quench starts. You could also run a sniffer on the line for additional information.


RE: ICMP source quench problem

I gathered some new info :

1. This problem for some reason does not concern any of the Avayas
2. Quench messages are for sure generated by server:
- when "show ip traffic" command is issued the 'Quench' counter for 'Rcvd' only increases in the same time Avaya which is between server and Ciscos shows no Quench counters was sent - so server must have sent it.

Still don`t know what the reason for such a behaviour of Avaya  devices only is.


RE: ICMP source quench problem

For HP-UX management, just type "sam", and see if you can view something. Also,"gsp" will show the error logs---type sam or gsp, without the quotes. Very user-friendly.


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