[troubleshooting sharing--network service going down] network going down after some operations at the server down

Created: May 27, 2018 18:40:31Latest reply: May 27, 2018 19:03:57 464 1 0 0
I met an axample of net service going down issue, after finished the troubleshooting, we found that the root cause was due to a loop between access switch and server. 

as we know, some server also has a fabric transmiting switch inside, for example, E9000 server, if we connnect the server to switch and configure it incorrectly, it may raise a loop in the network.

The Layer 2 loop always has bad impact for the whole network since it can cause huge ARP broadcast packets in the network, and further it will affect normal ARP learning. If Gateway couldn’t learn ARP in time, the service will be down.

 

As we know, even the port on access switch is just 1G, but 1G can include huge ARP packets, the core switch couldn’t handle so many ARP packets in time, and most of them are dropped by cpu-defend and ARP anti-attack.


so, for the service going down issue, we can always check the ARP packets with bellow commands:


display cpu-defend statistics all  ///to check if there are quite a lot of ARP packets were dropped by cpu-defend.

display arp anti-attack record   ///to check if there are quite a lot of ARP packets were dropped by anti-attack


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wissal  Visitor   Created May 27, 2018 19:03:57 Helpful(0) Helpful(0)

useful document, thanks
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