[Openstack] can anybody help to explain how the packet of ping shoule be forwarded from vm

Sam Lee lixq2000 at gmail.com
Tue Sep 23 07:13:55 UTC 2014


I am not sure you are right or not.    Bridge is a virtual switch, if we
want to communicate outside world using bridge, we must attach a physical
devices to bridge. eth0 is just the device.

2014-09-23 15:04 GMT+08:00 严超 <yanchao727 at gmail.com>:

> eth0 is virtualized as br100 , as your command show:
>
> 2: eth0:  mtu 1500 qdisc pfifo_fast *master br100 state UP* qlen 1000
>     link/ether 00:1e:67:6a:8b:c9 brd ff:ff:ff:ff:ff:ff
>     inet6 fe80::21e:67ff:fe6a:8bc9/64 scope link
>        valid_lft forever preferred_lft forever
>
> So I think packages would be handled by eth0. Right?
>
>
> *Best Regards!*
>
>
> *Chao Yan--------------**My twitter:Andy Yan @yanchao727
> <https://twitter.com/yanchao727>*
>
>
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>
> 2014-09-23 14:33 GMT+08:00 Sam Lee <lixq2000 at gmail.com>:
>
>> I set up an openstack environment using nova-network with multi_host mode.
>>
>> created network info as below,
>>
>> root at ubuntu:~# nova network-show e77b754d-5a89-41fd-8c82-69051e69c4ed
>> +---------------------+--------------------------------------+
>> | Property            | Value                                |
>> +---------------------+--------------------------------------+
>> | bridge              | br100                                |
>> | vpn_public_port     | None                                 |
>> | dhcp_start          | 172.16.10.202                        |
>> | bridge_interface    | eth0                                 |
>> | updated_at          | None                                 |
>> | id                  | e77b754d-5a89-41fd-8c82-69051e69c4ed |
>> | cidr_v6             | None                                 |
>> | deleted_at          | None                                 |
>> | gateway             | 172.16.10.1                          |
>> | rxtx_base           | None                                 |
>> | label               | private                              |
>> | priority            | None                                 |
>> | project_id          | None                                 |
>> | vpn_private_address | None                                 |
>> | deleted             | 0                                    |
>> | vlan                | None                                 |
>> | broadcast           | 172.16.10.207                        |
>> | netmask             | 255.255.255.248                      |
>> | injected            | False                                |
>> | cidr                | 172.16.10.200/29                     |
>> | vpn_public_address  | None                                 |
>> | multi_host          | True                                 |
>> | dns2                | None                                 |
>> | created_at          | 2014-09-11T07:58:13.000000           |
>> | host                | None                                 |
>> | gateway_v6          | None                                 |
>> | netmask_v6          | None                                 |
>> | dns1                | 8.8.4.4                              |
>> +---------------------+--------------------------------------+
>> Note: 172.16.10.1 is the physical gateway
>>
>> route info of the host as below:
>>
>> Kernel IP routing table
>> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
>> 0.0.0.0         172.16.10.1     0.0.0.0         UG    100    0        0 eth1
>> 10.10.100.0     0.0.0.0         255.255.255.0   U     0      0        0 br100
>> 172.16.10.0     0.0.0.0         255.255.255.0   U     0      0        0 eth1
>> 172.16.10.200   0.0.0.0         255.255.255.248 U     0      0        0 br100
>>
>> three instances has been created as below,
>>
>> root at ubuntu:~# nova list
>> +--------------------------------------+-------+--------+-----------------------+
>> | ID                                   | Name  | Status | Networks              |
>> +--------------------------------------+-------+--------+-----------------------+
>> | 5867fa88-de5c-4656-9811-5c86128b786b | test3 | ACTIVE | private=172.16.10.202 |
>> | 272f8d4f-f924-488b-855f-7f53a2372708 | test4 | ACTIVE | private=172.16.10.204 |
>> | aec01738-996f-42dc-a921-1c859c79ffed | test5 | ACTIVE | private=172.16.10.205 |
>> +--------------------------------------+-------+--------+-----------------------+
>>
>> ip info of host:
>>
>> root at ubuntu:~# ip a
>> 1: lo:  mtu 16436 qdisc noqueue state UNKNOWN
>>     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>>     inet 127.0.0.1/8 scope host lo
>>     inet 169.254.169.254/32 scope link lo
>>     inet6 ::1/128 scope host
>>        valid_lft forever preferred_lft forever
>> 2: eth0:  mtu 1500 qdisc pfifo_fast master br100 state UP qlen 1000
>>     link/ether 00:1e:67:6a:8b:c9 brd ff:ff:ff:ff:ff:ff
>>     inet6 fe80::21e:67ff:fe6a:8bc9/64 scope link
>>        valid_lft forever preferred_lft forever
>> 3: eth1:  mtu 1500 qdisc pfifo_fast state UP qlen 1000
>>     link/ether 00:1e:67:6a:8b:c8 brd ff:ff:ff:ff:ff:ff
>>     inet 172.16.10.16/24 brd 172.16.10.255 scope global eth1
>>     inet6 fe80::21e:67ff:fe6a:8bc8/64 scope link
>>        valid_lft forever preferred_lft forever
>> 5: br100:  mtu 1500 qdisc noqueue state UP
>>     link/ether 00:1e:67:6a:8b:c9 brd ff:ff:ff:ff:ff:ff
>>     inet 172.16.10.203/29 brd 172.16.10.207 scope global br100
>>     inet 10.10.100.52/24 brd 10.10.100.255 scope global br100
>>     inet6 fe80::44c7:b4ff:fe0c:3f/64 scope link
>>        valid_lft forever preferred_lft forever
>> 6: vnet0:  mtu 1500 qdisc pfifo_fast master br100 state UNKNOWN qlen 500
>>     link/ether fe:16:3e:0f:03:49 brd ff:ff:ff:ff:ff:ff
>>     inet6 fe80::fc16:3eff:fe0f:349/64 scope link
>>        valid_lft forever preferred_lft forever
>> 7: vnet1:  mtu 1500 qdisc pfifo_fast master br100 state UNKNOWN qlen 500
>>     link/ether fe:16:3e:b3:d8:a1 brd ff:ff:ff:ff:ff:ff
>>     inet6 fe80::fc16:3eff:feb3:d8a1/64 scope link
>>        valid_lft forever preferred_lft forever
>> 8: vnet2:  mtu 1500 qdisc pfifo_fast master br100 state UNKNOWN qlen 500
>>     link/ether fe:16:3e:0e:7a:0d brd ff:ff:ff:ff:ff:ff
>>     inet6 fe80::fc16:3eff:fe0e:7a0d/64 scope link
>>        valid_lft forever preferred_lft forever
>>
>> mac table of br100:
>>
>> root at ubuntu:~# brctl showmacs br100
>> port no mac addr                is local?       ageing timer
>>   1     00:0c:29:27:9d:7e       no                16.79
>>   1     00:0c:29:27:9d:88       no                 5.49
>>   1     00:0c:29:58:9a:64       no                31.86
>>   1     00:0c:29:f3:cf:7b       no                21.28
>>   1     00:12:7f:7d:37:a1       no                35.54
>>   1     00:14:5e:ac:7c:b5       no                26.20
>>   1     00:14:5e:e8:03:d1       no                13.31
>>   1     00:14:f2:a8:00:81       no                 1.11
>>   1     00:1e:67:45:85:ad       no                14.02
>>   1     00:1e:67:64:ed:c9       no                10.10
>>   1     00:1e:67:64:ee:a5       no                 9.38
>>   1     00:1e:67:6a:8b:c9       yes                0.00
>>   1     00:1e:67:97:17:ee       no                52.97
>>   1     52:54:00:01:40:23       no                10.72
>>   1     52:54:00:1c:71:3d       no                 5.50
>>   1     52:54:00:47:9c:ee       no                 8.70
>>   1     52:54:00:b8:aa:45       no                 9.79
>>   1     52:54:00:ee:60:44       no                 7.61
>>   1     5c:f3:fc:00:0e:da       no                56.27
>>   1     5c:f3:fc:00:ad:02       no                 1.13
>>   1     6c:ae:8b:51:49:12       no                 0.64
>>   1     8a:62:65:05:8d:02       no                 5.38
>>   1     ae:2a:9d:74:11:03       no               155.47
>>   1     e4:1f:13:75:47:e0       no                 8.24
>>   1     e4:1f:13:fc:a8:21       no               176.11
>>   1     fa:16:3e:00:c8:ce       no                 0.38
>>   1     fa:16:3e:05:61:a3       no                 4.29
>>   4     fa:16:3e:0e:7a:0d       no                11.35
>>   2     fa:16:3e:0f:03:49       no                 9.90
>>   1     fa:16:3e:2c:6c:55       no                24.90
>>   1     fa:16:3e:2d:f0:f0       no                 7.40
>>   1     fa:16:3e:3b:35:e1       no                27.88
>>   1     fa:16:3e:3f:1a:0c       no                 9.18
>>   1     fa:16:3e:49:d6:54       no                10.57
>>   1     fa:16:3e:4a:47:6e       no                13.07
>>   1     fa:16:3e:61:d5:0c       no                24.14
>>   1     fa:16:3e:6b:89:c1       no                25.96
>>   1     fa:16:3e:85:80:df       no                 3.74
>>   1     fa:16:3e:8d:a4:da       no                28.20
>>   1     fa:16:3e:9f:bb:0c       no                13.65
>>   1     fa:16:3e:a6:88:1d       no                24.17
>>   3     fa:16:3e:b3:d8:a1       no                 6.07
>>   1     fa:16:3e:c8:42:0d       no                27.80
>>   1     fa:16:3e:ca:a8:8e       no                 4.70
>>   1     fa:16:3e:e8:a7:9b       no                27.31
>>   4     fe:16:3e:0e:7a:0d       yes                0.00
>>   2     fe:16:3e:0f:03:49       yes                0.00
>>   3     fe:16:3e:b3:d8:a1       yes                0.00
>>
>> arp table of instance test5:
>>
>> [root at test5 ~]# arp -a
>> ? (172.16.10.203) at 00:1e:67:6a:8b:c9 [ether] on eth0
>> ? (172.16.10.1) at 00:12:7f:7d:37:a1 [ether] on eth0
>>
>> route info of instance test5
>>
>> [root at test5 ~]# route -n
>> Kernel IP routing table
>> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
>> 172.16.10.1     0.0.0.0         255.255.255.255 UH    0      0        0 eth0
>> 172.16.10.200   0.0.0.0         255.255.255.248 U     1      0        0 eth0
>> 192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
>> 0.0.0.0         172.16.10.1     0.0.0.0         UG    0      0        0 eth0
>>
>> I ping www.sina.com.cn in instances test5(172.16.10.205)
>>
>> [root at test5 ~]# ping www.sina.com.cn
>> PING ara.sina.com.cn (58.63.236.35) 56(84) bytes of data.
>> 64 bytes from 58.63.236.35: icmp_seq=1 ttl=49 time=38.4 ms
>> 64 bytes from 58.63.236.35: icmp_seq=2 ttl=49 time=38.5 ms
>> 64 bytes from 58.63.236.35: icmp_seq=3 ttl=49 time=38.2 ms
>> ^C
>> --- ara.sina.com.cn ping statistics ---
>> 3 packets transmitted, 3 received, 0% packet loss, time 2436ms
>> rtt min/avg/max/mdev = 38.259/38.427/38.536/0.256 ms
>>
>> In my option, the packet will go through as follow,
>> 1. vm eth0
>> 2. br100
>> 3. according the mac table of switch br100, the packet will go through to
>> port 1
>>
>> the next step has always puzzled me
>> 4. the packet arrived at host eth0. Once the packet arrived eth0, it will
>> be processed by iptables chains, INPUT, PREROUTING, kernel routing, OUTPUT
>> and so on. the destination address is 58.63.236.35, based on the kernel
>> routing table, the packet will be processed by eth1. *In fact, eth0
>> processes it.*can anyone explain why??
>>
>>
>>
>>>>
>> Thanks in advance.
>>
>>
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