On Feb 20, 2013, at 10:45 AM, Anton Shterenlikht <[email protected]> wrote:

>       From: Fleuriot Damien <[email protected]>
>       To: [email protected]
>       Subject: Re: cannot ssh into a box with DHCP assigned IP address
>       Date: Wed, 20 Feb 2013 10:31:22 +0100
>       Cc: [email protected]
> 
>       On Feb 20, 2013, at 10:28 AM, Anton Shterenlikht <[email protected]> 
> wrote:
> 
>       > I have a laptop with FreeBSD -current,
>       > with ip address assigned via DHCP.
>       > The laptop has neither a static ip address,
>       > nor a domain.
>       > 
>       > I can ping the laptop fine, but cannot
>       > ssh into it. The sshd is running, /etc/ssh/ssd_config
>       > seems fine, /etc/hosts.allow is fine.
>       > However, /etc/hosts is just the default:
>       > 
>       > #
>       > ::1                     localhost localhost.my.domain
>       > 127.0.0.1               localhost localhost.my.domain
>       > #
>       > 
>       > Is it the lack of a domain that prevents
>       > me from getting ssh access?
>       > I try to ssh with just a dynamic ip address,
>       > for which ping seems to work fine.
>       > Or is the problem somewhere else?
>       > 
>       > I'm not even sure I'm asking the right
>       > questions.
>       > 
>       > Thanks
>       > 
>       > Anton
> 
> 
>       First, check what ports SSH listens on:
>       sockstat | grep ssh
> 
> root@zzz:~ # sockstat | grep ssh
> mexas    ssh        16193 3  tcp4   172.21.220.12:20541   137.222.187.241:22
> root     sshd       1091  3  tcp6   *:22                  *:*
> root     sshd       1091  4  tcp4   *:22                  *:*
> root@zzz:~ #
> 
> I also see:
> 
> /var/log/auth.log:Feb 18 11:54:25 zzz sshd[1091]: Server listening on :: port 
> 22
> .
> /var/log/auth.log:Feb 18 11:54:25 zzz sshd[1091]: Server listening on 0.0.0.0 
> po
> rt 22.
> 
> Is 0.0.0.0 expected?
> 

0.0.0.0 = * = all IPs / interfaces



> Anything else I should check in the logs?
> 

Not that I'm aware of



> 
>       Then, assuming SSH indeed listens on *:22 ,
>        check if you have a firewall running that
>        could be preventing packets from reaching your box.
> 
> I don't think so.
> There's nothing in the kernel config
> 
>       By the way, do you get a login prompt at all,
>        over SSH, or just a plain timeout or connection reset ?
> 
> Just a timeout:
> 
> root@zzz:~ # ifconfig wlan0
> wlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
>        ether 00:21:5c:50:68:c3
>        inet 172.21.220.12 netmask 0xfffffc00 broadcast 255.255.255.255
>        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
>        media: IEEE 802.11 Wireless Ethernet OFDM/54Mbps mode 11g
>        status: associated
>        ssid eduroam channel 1 (2412 MHz 11g) bssid 00:3a:98:62:cd:a0
>        country US authmode WPA2/802.11i privacy ON deftxkey UNDEF
>        AES-CCM 2:128-bit AES-CCM 3:128-bit txpower 14 bmiss 10 scanvalid 450
>        bgscan bgscanintvl 300 bgscanidle 250 roam:rssi 7 roam:rate 5
>        protmode CTS wme roaming MANUAL
> root@zzz:~ #
> 
> TZAV> ping 172.21.220.12
> PING 172.21.220.12 (172.21.220.12): 56 data bytes
> 64 bytes from 172.21.220.12: icmp_seq=0 ttl=60 time=2.056 ms
> 64 bytes from 172.21.220.12: icmp_seq=1 ttl=60 time=1.766 ms
> ^C
> 
> TZAV> ssh 172.21.220.12
> ssh: connect to host 172.21.220.12 port 22: Operation timed out
> TZAV>
> 
> Thanks
> 
> Anton
> 



Run this on your server:

tcpdump -ni wlan0 ip and port 22



Then try to ssh to the box, see if SYN packets arrive, see if your box sends 
SYN/ACK back.

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