[PLUG] Cant always SSH to box but can ping it for days

Jason Kirtland plug at lists.discorporate.us
Tue Nov 14 17:57:20 UTC 2006


Do you have reverse DNS for your 10.x.x.x network?  No PTRs can make 
SSH and route act just like that.

-=j

Jeff wrote:
> Hi all I need some advice. I am fighting a bit of a ghost and don't
> know where else to look. I reinstalled my edge box this weekend and
> have gone with vmware to containerize all my virtual appliances.
> Should make developing and experimenting much easier. Anyway I am
> having a problem with the base server responding to tcp traffic. It
> is sporadic at best and most of the time it won't respond at all. I
> can always ping the eth0 interface but cannot ssh to it dependably
> from my PC. Note that when I cannot connect I get a "connection
> refused" error. Me thinks this is typical of a firewall or acl but
> there are none in between. The machine is a fresh install of ubuntu
> server with openssh, kernel source, a few libraries, and vmware
> server installed. On vm1 I have a pfsense server installed and it is
> working fine. I can access it via 443 with no problems and it is
> passing traffic just dandy. I must be missing something pretty basic
> here. Thanks for the help!
> (SORRY FOR THE POOR ASCI ART. I AM A VISUAL FELLER)
>
>        ---------                      --------
>  eth1  |       | eth0                 |      |
> -------|       |-------(           )--|      |
>    |   | ----- |   |   (dell switch)  |  PC  |
>  vmnet1|-|   |-|vmnet2 (           )  |      |
>        | |vm1| |                      |      |
>        | ----- |                      |      |
>        ---------                      --------
>
> Configuration:
> -(eth1) is up but is configured with an "ifconfig eth1 0.0.0.0" cmd
> I did this because I dont want any traffic to hit eth1 accept for the
> traffic destined for the vmnet1(which is bridged to eth1). Probably a
> better way to do this... Any tips welcome.. note I put an "up ifconfig
> eth1 0.0.0.0" line in my /etc/network/interfaces to do this.
> -(vmnet1) is up and has my external ip address. It is bridged via
> vmware to eth1
> -(eth0) is up and is 10.x.x.10. This is the int having the connection
> problems
> -(vmnet2) is up and is 10.x.x.1. This is the pfsense gateway. (note
> that 10.x.x.10 is showing up correctly in the arp tables on this
> gateway)
>
> Funny things I have noticed:
> - Even directly connected(eliminating the dell) to the box it will
> still fail.
> - The time to connect with ssh is very slow, I will get a username
> prompt and then will wait a good 6 seconds for a password prompt.
> - Also the route command is very slow to respond. It takes forever to
> get the default line.
> - I have tried to set the ip on eth1 to a private address ie
> 192.168.x.x and have also disabled it altogether. The changing of the
> address had no effect. The disabling of the interface seemed to help
> with the stability of the connection.
> - Unplugging the eth1 interface seems to help with stability(ssh is
> still slow to authenticate)
> - I have also shutdown the vm1 to make sure there were no conflicts
> and it didn't change anything.
> - I have swapped the configurations of eth0 and eth1 and still have
> the same results on different interfaces.
>
> Thanks all! sorry for the long post!
> jm
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