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Date:      Thu, 19 Jan 2012 16:16:03 +0100
From:      n dhert <ndhertbsd@gmail.com>
To:        freebsd-questions@freebsd.org
Subject:   Re: changed ip-adress, DNS lookups don't work anymore
Message-ID:  <CAEFCw4tg14fAjrd3sZE=H9d_h9aHbLDGzy5mpRiUY4iAWo8nyQ@mail.gmail.com>
In-Reply-To: <CAEFCw4svdewbz-Na=QYr6_rhu++4+A-6wDuiEtKdpgdmJN1xhw@mail.gmail.com>
References:  <CAEFCw4u4_ZYX4ekHx_Gm0pxj5M+8jQHjesdd0FoGxNhPRgOp5w@mail.gmail.com> <4F182A5A.30202@my.gd> <CAEFCw4svdewbz-Na=QYr6_rhu++4+A-6wDuiEtKdpgdmJN1xhw@mail.gmail.com>

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>
> - with UseDNS no, I can login quickly again..
> - I don't manage the DNS servers, can do anything there, but I do believe
> they do not receive anything
> since I now see, I can't even ping any of the three of tehm, specified in
> my /etc/resolv,conf file
> # ping 143.169.254.100
> - the /etc/resolv.conf file is OK (same as on other machines getting DHCP
> info from the same DHCP server)
>
> [admin@pclinwi7475old 75.126 ~]$ netstat -m
> 258/267/525 mbufs in use (current/cache/total)
> 256/134/390/16704 mbuf clusters in use (current/cache/total/max)
> 256/128 mbuf+clusters out of packet secondary zone in use (current/cache)
> 0/2/2/8352 4k (page size) jumbo clusters in use (current/cache/total/max)
> 0/0/0/4176 9k jumbo clusters in use (current/cache/total/max)
> 0/0/0/2088 16k jumbo clusters in use (current/cache/total/max)
> 576K/342K/919K bytes allocated to network (current/cache/total)
> 0/0/0 requests for mbufs denied (mbufs/clusters/mbuf+clusters)
> 0/0/0 requests for jumbo clusters denied (4k/9k/16k)
> 0/4/4432 sfbufs in use (current/peak/max)
> 0 requests for sfbufs denied
> 0 requests for sfbufs delayed
> 0 requests for I/O initiated by sendfile
> 0 calls to protocol drain routines
> [admin@pclinwi7475old 75.126 ~]$ ifconfig
> em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
>
> options=209b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,WOL_MAGIC>
>         ether 00:0b:db:53:3e:15
>         inet 143.129.75.126 netmask 0xffffff00 broadcast 143.129.75.255
>         media: Ethernet autoselect (100baseTX <full-duplex>)
>         status: active
> plip0: flags=8810<POINTOPOINT,SIMPLEX,MULTICAST> metric 0 mtu 1500
> lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
>         options=3<RXCSUM,TXCSUM>
>         inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3
>         inet6 ::1 prefixlen 128
>         inet 127.0.0.1 netmask 0xff000000
>         nd6 options=3<PERFORMNUD,ACCEPT_RTADV>
> I'm believing now there is still something wrong on the firewall
> something in the cache referring to the old IP address ???
>
> I use shorewall on a Ubuntu 11.04 ...
>
>
> 2012/1/19 Damien Fleuriot <ml@my.gd>
>
>>
>>
>> On 1/19/12 3:32 PM, n dhert wrote:
>> > FreeBSD 8.2. system.
>> > Gets is TCP/IP parameters (and DNS name-servers IPs) from a DHCP server,
>> > with a fixed IP address
>> > (the system always gets the same IP, based on its MAC address as
>> specified
>> > in the DHCP config file)
>> >
>> > Now I wanted the system to have a different IP address.
>> > Changed the DHCP server config accordingly.
>> > Reboot. OK, from  $ ifconfig -a I can see it received the new IP.
>> >
>> > But DNS lookups don't work any longer ..
>> > $ host xxx.yyy.zzz.com
>> > ;; connection timed out; no servers could be reached
>> >
>> > The system is behind a firewall, but there are NO errors logged relating
>> > to the (new) IP address.
>> > Other FreeBSD-8.2 systems using the same DHCP server, configured in
>> exactly
>> > the same way, work perfectly well.
>> >
>> > I can SSH to the sytem, but it takes 20 or 30 seconds before the
>> Password:
>> > prompt appears (normally should
>> > be immediate)
>> > Once in the system, starting my alpine mail-client, it takes a minute
>> or so
>> > to display the messages (normally this should be immediate)
>> > Also at boot of the system there is wait for a 2,5 minutes somewhere in
>> the
>> > series of Starting <deamon>.
>> > Probably these three phenomena have the same cause: DNS lookups don't
>> work
>> >
>> > any idea what can be wrong ??
>> > I've looked and compared with other systems, can't find it ...
>> >
>>
>>
>> First, add "UseDNS no" to either /etc/ssh/sshd_config or
>> /usr/local/etc/ssh/sshd_config
>>
>> That'll allow you to log in via SSH without the server performing DNS
>> lookups, which are rather useless anyway.
>>
>> Second, you should run "tcpdump" on your DNS host to check if you're
>> actually receiving requests from your freebsd box.
>>
>>
>> Also, post your /etc/resolv.conf , "netstat -rn" and "ifconfig"
>>
>> I'd also be interested in the relevant parts of your firewalling config
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>
>



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