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本帖最后由 dxcheng 于 2017-07-31 14:12 编辑
Hi,all,
网络环境:
openstack网络下创建两个linux centos虚拟机,一个单网卡,另外一个多网卡,如下图所示:
问题描述:
在172.16.101.3这台单网卡虚拟机上ping 另外一台虚拟机的eth0 ip 172,16.101.7是可以通的。
但是,ping另外一块网卡172.16.101.10时,失败如下:
[root@centos2 ~]# ping 172.16.101.10
PING 172.16.101.10 (172.16.101.10) 56(84) bytes of data.
From 172.16.101.3 icmp_seq=1 Destination Host Unreachable
From 172.16.101.3 icmp_seq=2 Destination Host Unreachable
查看arp信息如下:
[root@centos2 ~]# arp -a
host-172-16-101-7.openstacklocal (172.16.101.7) at fa:16:3e:3d:73:55 [ether] on eth0
host-172-16-101-10.openstacklocal (172.16.101.10) at <incomplete> on eth0
我的分析:
在另外一台虚拟机上通过tcpdump抓包分析,可以看到ping eth1(172.16.101.10)时,eth0收到arp请求,
并做了回复,不过是将这个ip地址解析为了eth0本身的mac地址。实际的网卡eth1能收到这个arp请求,但是没有响应。
[root@centos3 ~]# tcpdump -i eth0 arp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
06:13:49.512803 ARP, Request who-has host-172-16-101-10.openstacklocal tell host-172-16-101-3.openstacklocal, length 28
06:13:49.512827 ARP, Reply host-172-16-101-10.openstacklocal is-at fa:16:3e:3d:73:55 (oui Unknown), length 28
[root@centos3 ~]# tcpdump -i eth1 arp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
06:14:17.520515 ARP, Request who-has host-172-16-101-10.openstacklocal tell host-172-16-101-3.openstacklocal, length 28
06:14:18.522618 ARP, Request who-has host-172-16-101-10.openstacklocal tell host-172-16-101-3.openstacklocal, length 28
06:14:20.518783 ARP, Request who-has host-172-16-101-10.openstacklocal tell host-172-16-101-3.openstacklocal, length 28
而且ARP发送端,一直也是没有收到ARP响应:
[root@centos2 ~]# tcpdump -i eth0 arp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
06:21:48.862254 ARP, Request who-has host-172-16-101-10.openstacklocal tell node1, length 28
06:21:49.863688 ARP, Request who-has host-172-16-101-10.openstacklocal tell node1, length 28
06:21:50.865690 ARP, Request who-has host-172-16-101-10.openstacklocal tell node1, length 28
我的问题:
1. eth0 为什么回复eth1的ARP请求?
2. eth1 为什么没有回复ARP请求?
PS. Linux core 3.10.0-514.26.2.el7.x86_64, CentOS Linux release 7.3.1611 (Core)
Thanks,
Cheng
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