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Re: [Xen-users] Simple networking problem - DNS

To: "Julius Spencer" <julius@xxxxxxxxx>
Subject: Re: [Xen-users] Simple networking problem - DNS
From: "Damon Brown" <damon@xxxxxxxxxxxxxx>
Date: Tue, 23 May 2006 08:30:42 -0700
Cc: Xen Users <xen-users@xxxxxxxxxxxxxxxxxxx>
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Thats interesting, I have the same issues ..... right when I brought up the DomU (which is just a clone of dom0) my DNS wouldnt resolve anylonger.  I was planning on trying to work through it tonight. 

Im using CentOS 4.3 with a source compile of xen 3.0.2-2

On 5/22/06, Julius Spencer <julius@xxxxxxxxx> wrote:
Hi,

I have spent a fair amount of time trying to solve this problem and
tried things like disabling checksums etc.

The problem is like this:
1. I boot my dom0 without xend running and I can resolve and ping google.
2. I start xend (without and domU domains up) and after a while I can no
longer resolve domain names, but I can ping the public IP addresses.
3. I start up a domU (xm create -c xyz) and I have the same issue there
too (not surprising as it is using the same bridge).

The following is a list of info after step 3 for the dom0 and domU both
of which can ping public IP addresses but not resolve domain names. The
tcpdump is being run on dom0.


Any ideas? It seems like it must be a pretty specific configuration change.

Cheers,
Julius.

##DNS Request from dom0
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 96
bytes
15:25:40.336919 IP (tos 0x0, ttl  64, id 33990, offset 0, flags [DF],
proto 17, length: 56) 192.168.1.201.32774 > 192.168.1.1.domain: [udp sum
ok]  46934+ A? google.com. (28)
15:25:40.336966 IP (tos 0x0, ttl  64, id 33990, offset 0, flags [DF],
proto 17, length: 56) 192.168.1.201.32774 > 192.168.1.1.domain: [udp sum
ok]  46934+ A? google.com. (28)

##DNS Request from domU
15:25:51.968703 arp who-has 192.168.1.1 tell 192.168.1.231
15:25:51.988626 arp who-has 192.168.1.231 tell 192.168.1.201
15:25:51.988720 arp reply 192.168.1.231 is-at 00:16:3e:00:00:03
15:25:51.988737 IP (tos 0xc0, ttl  64, id 62783, offset 0, flags [none],
proto 1, length: 84) 192.168.1.201 > 192.168.1.231: icmp 64: host
192.168.1.1 unreachable - admin prohibited for IP (tos 0x0, ttl  64, id
64204, offset 0, flags [DF], proto 17, length: 56) 192.168.1.231.32769 >
192.168.1.1.domain:  16734+[|domain]
15:25:51.988880 IP (tos 0xc0, ttl  64, id 62784, offset 0, flags [none],
proto 1, length: 84) 192.168.1.201 > 192.168.1.231: icmp 64: host
192.168.1.1 unreachable - admin prohibited for IP (tos 0x0, ttl  64, id
64210, offset 0, flags [DF], proto 17, length: 56) 192.168.1.231.32769 >
192.168.1.1.domain:  16734+[|domain]

##NTP Reuqest from dom0
15:25:49.518708 IP (tos 0x10, ttl  64, id 113, offset 0, flags [DF],
proto 17, length: 76) 192.168.1.201.ntp > 194.100.206.70.ntp : [udp sum
ok] NTPv4, length 48
         Client, Leap indicator:  (0), Stratum 3, poll 7s, precision -20
         Root Delay: 0.414093, Root dispersion: 0.031051, Reference-ID:
194.100.206.70
           Reference Timestamp:  3357343418.923047999 (2006/05/23 15:23:38)
           Originator Timestamp: 3357343418.718721999 (2006/05/23 15:23:38)
           Receive Timestamp:    3357343418.923047999 (2006/05/23 15:23:38)
           Transmit Timestamp:   3357343549.518689999 (2006/05/23 15:25:49)
             Originator - Receive Timestamp:  +0.204326000
             Originator - Transmit Timestamp: +130.799968000
15:25:49.920925 IP (tos 0x0, ttl  39, id 0, offset 0, flags [DF], proto
17, length: 76) 194.100.206.70.ntp > 192.168.1.201.ntp: [udp sum ok]
NTPv4, length 48
         Server, Leap indicator:  (0), Stratum 2, poll 7s, precision -16
         Root Delay: 0.011306, Root dispersion: 0.019927, Reference-ID:
192.36.144.22
           Reference Timestamp:  3357343336.749644999 (2006/05/23 15:22:16)
           Originator Timestamp: 3357343549.518689999 (2006/05/23 15:25:49)
           Receive Timestamp:    3357343549.716807999 (2006/05/23 15:25:49)
           Transmit Timestamp:   3357343549.716845999 (2006/05/23 15:25:49)
             Originator - Receive Timestamp:  +0.198118000
             Originator - Transmit Timestamp: +0.198156000

#####ifconfig dom0
eth0      Link encap:Ethernet  HWaddr 00:11:25:A4:6C:4B
           inet addr:192.168.1.201  Bcast: 192.168.1.255  Mask:255.255.255.0
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:425 errors:0 dropped:0 overruns:0 frame:0
           TX packets:1327 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:224495 (219.2 KiB)  TX bytes:126651 (123.6 KiB)

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:963 errors:0 dropped:0 overruns:0 frame:0
           TX packets:963 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:98272 (95.9 KiB)  TX bytes:98272 (95.9 KiB)

peth0     Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
           UP BROADCAST RUNNING NOARP MULTICAST  MTU:1500  Metric:1
           RX packets:1029 errors:0 dropped:0 overruns:0 frame:0
           TX packets:403 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:431691 (421.5 KiB)  TX bytes:47343 (46.2 KiB)
           Interrupt:16

vif0.0    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:1327 errors:0 dropped:0 overruns:0 frame:0
           TX packets:425 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:126651 (123.6 KiB)  TX bytes:224495 ( 219.2 KiB)

vif1.0    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:74 errors:0 dropped:0 overruns:0 frame:0
           TX packets:84 errors:0 dropped:22 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:4764 (4.6 KiB)  TX bytes:6566 (6.4 KiB)

xenbr0    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:668 errors:0 dropped:0 overruns:0 frame:0
           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:195790 (191.2 KiB)  TX bytes:0 ( 0.0 b)

###ifconfig domU
eth0      Link encap:Ethernet  HWaddr 00:16:3E:00:00:03
           inet addr:192.168.1.231  Bcast:192.168.1.255  Mask: 255.255.255.0
           inet6 addr: fe80::216:3eff:fe00:3/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:84 errors:0 dropped:0 overruns:0 frame:0
           TX packets:74 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:6566 (6.4 KiB)  TX bytes:4764 (4.6 KiB)

lo        Link encap:Local Loopback
           inet addr:127.0.0.1  Mask:255.0.0.0
           inet6 addr: ::1/128 Scope:Host
           UP LOOPBACK RUNNING  MTU:16436  Metric:1
           RX packets:8 errors:0 dropped:0 overruns:0 frame:0
           TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:560 (560.0 b)  TX bytes:560 (560.0 b)

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--
Damon Brown
Web Application Developer and Consultant
e-mail: damon@xxxxxxxxxxxxxx
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