Re: [Xen-users] Strangness with IP's

[Rudi Ahlers <Rudi@xxxxxxxxxxx>]

On Fri, Feb 18, 2011 at 2:03 AM, Rus Foster <twattycake@xxxxxxxxx> wrote:
> We've got a problem we've not come across before. We are running xen
> 3.4.3 on a known good configuration
>
> We have the subnet 109.169.72.128/25 pointing to a server with
> 109.169.72.129 as the default GW
>
> Random IP's in the subnet will not route from a domU (Xen PV and Xen
> HVM))to the default gw
>
> An IP will work on one domU but not another
>
> If the IP is bound to eth0:0 on the dom0 it works fine.
>
> Our configuration file for an effected VM is
>
> kernel     = '/boot/solus-vmlinuz'
> ramdisk    = '/boot/solus-initrd.img'
> #bootloader = '/usr/bin/pygrub'
> extra      = ''
> memory     = 512
> hostname   = 'blah'
> cpu_weight = 256
> name       = 'vm5952'
> vif        = ['ip=109.169.72.235, vifname=vifvm5952.0, mac=00:16:3e:af:ec:d7']
> vnc        = 0
> vcpus      = 4
> vncviewer  = 0
> serial     = 'pty'
> disk       = ['phy:/dev/VolGroup00/vm5952_img,xvda1,w',
> 'phy:/dev/VolGroup00/vm5952_swap,xvda2,w']
> root       = '/dev/xvda1 ro'
>
> It boots fine to the console and within the VM the network
> configuration looks sane
>
> domU
>
> sh-3.00# ifconfig eth0
> eth0      Link encap:Ethernet  HWaddr 00:16:3E:AF:EC:D7
>          inet addr:109.169.72.235  Bcast:109.169.72.255  Mask:255.255.255.128
>          inet6 addr: fe80::16:3eff:feaf:ecd7/64 Scope:Link
>          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>          RX packets:1362 errors:0 dropped:0 overruns:0 frame:0
>          TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
>          collisions:0 txqueuelen:1000
>          RX bytes:88977 (86.8 KiB)  TX bytes:776 (776.0 b)
>          Interrupt:24
>
>
> sh-3.00# netstat -rn
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
> 109.169.72.128  0.0.0.0         255.255.255.128 U         0 0          0 eth0
> 169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
> 0.0.0.0         109.169.72.129  0.0.0.0         UG        0 0          0 eth0
>
> BUT
>
>
> sh-3.00# ping -c 1 109.169.72.129
> PING 109.169.72.129 (109.169.72.129) 56(84) bytes of data.
>
> --- 109.169.72.129 ping statistics ---
> 1 packets transmitted, 0 received, 100% packet loss, time 0ms
>
>
> On the node itself
>
>
> [root@8 xen]# brctl show
> bridge name     bridge id               STP enabled     interfaces
> eth0            8000.0025901d7134       no              vifvm5952.0
>                                                                peth0
>
>
>
> [root@8 xen]# xm info
> host                   : 8.xn.nj.damnvps.com
> release                : 2.6.18-194.32.1.el5xen
> version                : #1 SMP Wed Jan 5 18:44:24 EST 2011
> machine                : x86_64
> nr_cpus                : 16
> nr_nodes               : 1
> cores_per_socket       : 4
> threads_per_core       : 2
> cpu_mhz                : 2400
> hw_caps                :
> bfebfbff:2c100800:00000000:00000740:009ee3fd:00000000:00000001:00000000
> virt_caps              : hvm
> total_memory           : 98294
> free_memory            : 72498
> node_to_cpu            : node0:0-15
> node_to_memory         : node0:72498
> xen_major              : 3
> xen_minor              : 4
> xen_extra              : .3
> xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
> hvm-3.0-x86_32p hvm-3.0-x86_64
> xen_scheduler          : credit
> xen_pagesize           : 4096
> platform_params        : virt_start=0xffff800000000000
> xen_changeset          : unavailable
> cc_compiler            : gcc version 4.1.2 20080704 (Red Hat 4.1.2-48)
> cc_compile_by          : root
> cc_compile_domain      : gitco.tld
> cc_compile_date        : Sat Jan 22 14:01:09 CET 2011
> xend_config_format     : 4
>
> Any ideas are welcome...
>
> _______________________________________________
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> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
>


Generally, depending on your network (i.e routers, firewalls & managed
switches) if you move an IP from one machine to another (where the MAC
addresses differ) you would need to clear the ARP cache on the
router(s) for it to work properly


-- 
Kind Regards
Rudi Ahlers
SoftDux

Website: http://www.SoftDux.com
Technical Blog: http://Blog.SoftDux.com
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Cell: 082 554 7532

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