cannot ssh into a box with DHCP assigned IP address
ml at my.gd
Wed Feb 20 10:00:37 UTC 2013
On Feb 20, 2013, at 10:45 AM, Anton Shterenlikht <mexas at bristol.ac.uk> wrote:
> From: Fleuriot Damien <ml at my.gd>
> To: mexas at bristol.ac.uk
> Subject: Re: cannot ssh into a box with DHCP assigned IP address
> Date: Wed, 20 Feb 2013 10:31:22 +0100
> Cc: freebsd-questions at freebsd.org
> On Feb 20, 2013, at 10:28 AM, Anton Shterenlikht <mexas at bristol.ac.uk> 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 at zzz:~ # sockstat | grep ssh
> mexas ssh 16193 3 tcp4 172.21.220.12:20541 188.8.131.52:22
> root sshd 1091 3 tcp6 *:22 *:*
> root sshd 1091 4 tcp4 *:22 *:*
> root at zzz:~ #
> I also see:
> /var/log/auth.log:Feb 18 11:54:25 zzz sshd: Server listening on :: port 22
> /var/log/auth.log:Feb 18 11:54:25 zzz sshd: 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 at 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 at 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
> TZAV> ssh 172.21.220.12
> ssh: connect to host 172.21.220.12 port 22: Operation timed out
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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