Network changed / System DNS broken / Help Please - Redhat

This is a discussion on Network changed / System DNS broken / Help Please - Redhat ; my address ( whansen at corporate-image dot com ) After changing the network over from 192.168.0 to 192.168.33 I noticed that one of my perl apps was not sending mail out. Upon investigation it was not able to resolve outgoing ...

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Thread: Network changed / System DNS broken / Help Please

  1. Network changed / System DNS broken / Help Please

    my address ( whansen at corporate-image dot com )


    After changing the network over from 192.168.0 to 192.168.33 I noticed
    that one of my perl apps was not sending mail out. Upon investigation
    it was not able to resolve outgoing names properly. I discovered that
    nubers would work fine for everything but that DNS worked correctly
    some times and not correctly others.

    The new load ballancing router seems to choose randomly between the
    two WAN connections for each session. As the symptoms are consistant
    and not random I do not beleive this to be a source of trouble. Also
    both connections go to the same ISP so the two DNS servers are the
    same for both connections.

    I keep thinking I have missed something in re-configuring for the
    192.168.33 network. I have included notes on the network and all the
    important files/information I could think of below:


    1 Load ballancing router 192.168.100.100 acting as gateway and
    providing nat. connected to two internet connections. Routing http/etc
    to second router

    1 Secondary router 192.168.33.100 acting as gateway and providing nat.
    connected to lan. routing http/etc to server

    Ports are unhindered for outgoing connections. A half dozen win
    machines are experiencing no problems on the 192.168.33 network.



    [root@amanda root]# host www.sonic.net
    www.sonic.net has address 209.204.190.64
    [root@amanda root]# ping www.sonic.net
    ping: unknown host www.sonic.net
    [root@amanda root]# ping 209.204.190.64
    PING 209.204.190.64 (209.204.190.64) from 192.168.33.211 : 56(84)
    bytes of data.
    64 bytes from 209.204.190.64: icmp_seq=1 ttl=249 time=23.8 ms
    64 bytes from 209.204.190.64: icmp_seq=2 ttl=251 time=36.6 ms
    64 bytes from 209.204.190.64: icmp_seq=3 ttl=251 time=57.1 ms

    --- 209.204.190.64 ping statistics ---
    3 packets transmitted, 3 received, 0% loss, time 2021ms
    rtt min/avg/max/mdev = 23.802/39.199/57.193/13.754 ms
    [root@amanda root]# traceroute www.sonic.net
    traceroute: unknown host www.sonic.net
    [root@amanda root]# traceroute 209.204.190.64
    traceroute to 209.204.190.64 (209.204.190.64), 30 hops max, 38 byte
    packets
    1 router (192.168.33.100) 2.119 ms 1.294 ms 1.263 ms
    2 192.168.100.100 (192.168.100.100) 3.150 ms 3.225 ms 3.200 ms
    3 64.142.68.1 (64.142.68.1) 15.960 ms 16.091 ms 16.008 ms
    4 64.142.32.1 (64.142.32.1) 171.970 ms 17.529 ms 17.946 ms
    5 64.142.0.85 (64.142.0.85) 19.669 ms 20.885 ms 20.911 ms
    6 208.201.224.120 (208.201.224.120) 23.108 ms 21.119 ms 21.271 ms
    [root@amanda root]#





    Red Hat Linux release 8.0 (Psyche)

    [root@amanda etc]# cat hosts
    # Do not remove the following line, or various programs
    # that require network functionality will fail.
    #servers

    #ivr boxes

    127.0.0.1 localhost
    192.168.33.211 amanda amanda.corporate-image.com
    192.168.33.210 clara
    192.168.33.220 mabel
    192.168.33.100 router

    [root@amanda etc]# cat /etc/resolv.conf
    domain corporate-image.com
    search corporate-image.com
    nameserver 208.201.224.11
    nameserver 208.201.224.33

    [root@amanda sysconfig]# cat network
    NETWORKING=yes
    HOSTNAME=amanda

    [root@amanda network-scripts]# cat ifcfg-eth0
    DEVICE=eth0
    BOOTPROTO=none
    BROADCAST=192.168.33.255
    IPADDR=192.168.33.211
    NETMASK=255.255.255.0
    NETWORK=192.168.33.0
    ONBOOT=yes
    USERCTL=no
    PEERDNS=no
    TYPE=Ethernet
    GATEWAY=192.168.33.100

    [root@amanda root]# ifconfig
    eth0 Link encap:Ethernet HWaddr 000:B7:88:53:66
    inet addr:192.168.33.211 Bcast:192.168.33.255
    Mask:255.255.255.0
    UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:13943 errors:0 dropped:0 overruns:0 frame:6
    TX packets:19084 errors:0 dropped:0 overruns:0 carrier:2
    collisions:388 txqueuelen:100
    RX bytes:2534201 (2.4 Mb) TX bytes:2652123 (2.5 Mb)
    Interrupt:21

    lo Link encap:Local Loopback
    inet addr:127.0.0.1 Mask:255.0.0.0
    UP LOOPBACK RUNNING MTU:16436 Metric:1
    RX packets:27 errors:0 dropped:0 overruns:0 frame:0
    TX packets:27 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:0
    RX bytes:3032 (2.9 Kb) TX bytes:3032 (2.9 Kb)

    [root@amanda etc]# cat host.conf
    order hosts,bind
    [root@amanda etc]#



  2. Re: Network changed / System DNS broken / Help Please

    In article ,
    whansenatsonicdotnet@usa.com wrote:
    > my address ( whansen at corporate-image dot com )
    >
    > After changing the network over from 192.168.0 to 192.168.33 I
    >noticed that one of my perl apps was not sending mail out. Upon investigation
    >it was not able to resolve outgoing names properly. I discovered that nubers
    >would work fine for everything but that DNS worked correctly some times and
    >not correctly others.
    >
    > The new load ballancing router seems to choose randomly between the two WAN
    > connections for each session. As the symptoms are consistant and not random I
    > do not beleive this to be a source of trouble. Also both connections go to
    > the same ISP so the two DNS servers are the same for both connections.
    >
    > I keep thinking I have missed something in re-configuring for the 192.168.33
    > network. I have included notes on the network and all the important
    > files/information I could think of below:


    -SNIP-

    So what does your /etc/nsswitch.conf file look like? I have never changed
    host.conf and I am not sure which takes precedence. It is possible that the
    'host' command uses host.conf but system name resolving uses nsswitch.conf,
    which would explain why 'host www.sonic.net' works.

    What does 'nslookup www.sonic.net' return? If it can't find anything but the
    'host' command does, I would suspect nsswitch.conf to be the problem.

    Does anybody know whether both nssswitch.conf and host.conf are used, and which
    for what purposes?

    Kevin

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