topic RE: slow ssh response on extreme switch in ExtremeSwitching (EXOS/Switch Engine)

slow ssh response on extreme switch

Yves_Haslimann — Wed, 03 May 2017 13:56:00 GMT

Hello,

I takes between 5 to 10 seconds until the SSH Login window appear, if I connect by SSH to the switch. I have the version 21.1.3.7 on the switches X440G2-48p-10G4 running. Do you have any idea, whats the reason for this?

Thanks, Yves

RE: slow ssh response on extreme switch

Frank — Wed, 03 May 2017 14:03:00 GMT

Hi,
my first guess would be: is your switch in DNS and can the IP be reverse-resolved by your workstation?

Frank

RE: slow ssh response on extreme switch

Nicolas_Nguyen — Wed, 03 May 2017 14:57:00 GMT

Hello Yves,

Does it happen will all terminals (putty, secureCRT, etc...) ?

There was a SSH bug in the previous version (21.1.1 and 21.1.2) but it should be corrected in your version.

Regards,
Nicolas

RE: slow ssh response on extreme switch

StephenW — Wed, 03 May 2017 17:18:00 GMT

I like both replies. Check DNS, and does it happen on all terminals. Are you saving the SSH Public key when connecting, or do you choose to download it each time?

RE: slow ssh response on extreme switch

Jeremy_Gibbs — Wed, 03 May 2017 17:23:00 GMT

I have the same problem with all EXOS switches running 22.2.1.5. I had several open at GTAC cases, but they were never corrected or fixed. After the initial slow login, SSH response normally when running commands. I can post the verbose output from my SSH client later.

RE: slow ssh response on extreme switch

Yves_Haslimann — Wed, 03 May 2017 18:32:00 GMT

Thanks for your replies. I checked DNS. But it's much faster by telnet, so in this case this seems to be a SSH problem, and not a DNS. And yes, I saved the key.

RE: slow ssh response on extreme switch

Frank — Wed, 03 May 2017 18:32:00 GMT

So your DNS is configured to reverse-resolve the IP address of the switch? You can check that in Unix/Linux via "dig -x ip.address" or in Windows with "nslookup ip.address" (and look at the last two lines, "Name" and "Address")

It's not really a DNS problem, it's that SSH has a problem if the reverse resolution fails.

RE: slow ssh response on extreme switch

Yves_Haslimann — Wed, 03 May 2017 18:32:00 GMT

No, I connect by the IP address to the switch. So the switch doesn't send any DNS requests.

RE: slow ssh response on extreme switch

Frank — Wed, 03 May 2017 18:32:00 GMT

Sorry that I was unclear: It's the workstation that you connect from that wants to be able to reverse-resolve the IP address of the switch.

RE: slow ssh response on extreme switch

Yves_Haslimann — Wed, 03 May 2017 18:32:00 GMT

I guess it was a DNS problem. I've configured the DNS AND the suffix, and it's good now. Thanks for your help. Besr regards.