[CentOS] Basic KVM networking question

Dale Dellutri daledellutri at gmail.com
Mon Sep 10 14:29:13 EDT 2012


On Mon, Sep 10, 2012 at 12:37 PM, Steve Thompson <smt at vgersoft.com> wrote:
> On Mon, 10 Sep 2012, Dale Dellutri wrote:
>
>> Routing problem?
>
> Not that I can see, but here is the info (omitting interfaces that are not
> up). I included on one KVM since the problem is common to the others, and
> they are all set up the same way.
>
> On the host:
>
> 3: em2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
>      link/ether 84:2b:2b:47:e8:7d brd ff:ff:ff:ff:ff:ff
>      inet6 fe80::862b:2bff:fe47:e87d/64 scope link
>         valid_lft forever preferred_lft forever
> 4: p1p1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
>      link/ether 00:1b:21:6f:2b:4c brd ff:ff:ff:ff:ff:ff
>      inet6 fe80::21b:21ff:fe6f:2b4c/64 scope link
>         valid_lft forever preferred_lft forever
> 7: br1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
>      link/ether 84:2b:2b:47:e8:7d brd ff:ff:ff:ff:ff:ff
>      inet 192.168.4.2/22 brd 192.168.7.255 scope global br1
>      inet6 fe80::862b:2bff:fe47:e87d/64 scope link
>         valid_lft forever preferred_lft forever
> 8: br2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
>      link/ether 00:1b:21:6f:2b:4c brd ff:ff:ff:ff:ff:ff
>      inet 192.168.0.2/22 brd 192.168.3.255 scope global br2
>      inet6 fe80::21b:21ff:fe6f:2b4c/64 scope link
>         valid_lft forever preferred_lft forever
> 10: virbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
>      link/ether 52:54:00:9d:ad:f7 brd ff:ff:ff:ff:ff:ff
>      inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
> 11: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 500
>      link/ether 52:54:00:9d:ad:f7 brd ff:ff:ff:ff:ff:ff
> 12: vnet0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 500
>      link/ether fe:54:00:13:73:28 brd ff:ff:ff:ff:ff:ff
>      inet6 fe80::fc54:ff:fe13:7328/64 scope link
>         valid_lft forever preferred_lft forever
> 13: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 500
>      link/ether fe:54:00:12:99:dd brd ff:ff:ff:ff:ff:ff
>      inet6 fe80::fc54:ff:fe12:99dd/64 scope link
>         valid_lft forever preferred_lft forever
> 14: vnet2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 500
>      link/ether fe:54:00:72:f5:33 brd ff:ff:ff:ff:ff:ff
>      inet6 fe80::fc54:ff:fe72:f533/64 scope link
>         valid_lft forever preferred_lft forever
>
> 192.168.122.0/24 dev virbr0  proto kernel  scope link  src 192.168.122.1
> 192.168.4.0/22 dev br1  proto kernel  scope link  src 192.168.4.2
> 192.168.0.0/22 dev br2  proto kernel  scope link  src 192.168.0.2
> default via 192.168.0.1 dev br2
>
> On KVM1:
>
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
>      link/ether 52:54:00:13:73:28 brd ff:ff:ff:ff:ff:ff
>      inet 192.168.3.253/22 brd 192.168.3.255 scope global eth0
>      inet6 fe80::5054:ff:fe13:7328/64 scope link
>         valid_lft forever preferred_lft forever
> 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
>      link/ether 52:54:00:12:99:dd brd ff:ff:ff:ff:ff:ff
>      inet 192.168.7.253/22 brd 192.168.7.255 scope global eth1
>      inet6 fe80::5054:ff:fe12:99dd/64 scope link
>         valid_lft forever preferred_lft forever
>
> 192.168.4.0/22 dev eth1  proto kernel  scope link  src 192.168.7.253
> 192.168.0.0/22 dev eth0  proto kernel  scope link  src 192.168.3.253
> default via 192.168.0.1 dev eth0
>
> On client A:
>
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
>      link/ether 00:14:22:27:9b:51 brd ff:ff:ff:ff:ff:ff
>      inet 192.168.0.172/22 brd 192.168.3.255 scope global eth0
>      inet6 fe80::214:22ff:fe27:9b51/64 scope link
>         valid_lft forever preferred_lft forever
>
> 192.168.0.0/22 dev eth0  proto kernel  scope link  src 192.168.0.172
> default via 192.168.0.2 dev eth0
>
> On client B:
>
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
>      link/ether 00:19:b9:c7:23:ad brd ff:ff:ff:ff:ff:ff
>      inet 192.168.5.241/22 brd 192.168.7.255 scope global eth0
>      inet6 fe80::219:b9ff:fec7:23ad/64 scope link
>         valid_lft forever preferred_lft forever
>
> 192.168.4.0/22 dev eth0  proto kernel  scope link  src 192.168.5.241
> default via 192.168.4.1 dev eth0

This looks like it should work for Client A, but maybe not for Client B (see
below).  So maybe it's a firewall problem (iptables chain FORWARD) on the
host?

Client B's default route is 192.168.4.1.  This address is not on the host.
Did you mean to use .2?  If not, is .1 aware of the routing to the
192.168.0.0/22 network?

-- 
Dale Dellutri


More information about the CentOS mailing list