openstack dhcp调试

openstack的dhcpserver默认值dnsmasq软件实施，经ps -ef | grep dnsmasq 查看。当虚拟机启动过程启动dhcp求，日志可以是在主机系统日志：

May 23 22:30:29 localhost dnsmasq-dhcp[5043]: DHCPDISCOVER(tapf7321a93-ac) fa:16:3e:33:0a:6a

May 23 22:30:29 localhost dnsmasq-dhcp[5043]: DHCPOFFER(tapf7321a93-ac) 10.0.0.41 fa:16:3e:33:0a:6a

May 23 22:30:29 localhost dnsmasq-dhcp[5043]: DHCPREQUEST(tapf7321a93-ac) 10.0.0.41 fa:16:3e:33:0a:6a

May 23 22:30:29 localhost dnsmasq-dhcp[5043]: DHCPACK(tapf7321a93-ac) 10.0.0.41 fa:16:3e:33:0a:6a host-10-0-0-41

能够看到dhcp四个阶段：发现、提供、选择、确认。

同一时候能够通过 nova console-log instance查看虚拟机启动日志

Starting network...

udhcpc (v1.18.5) started

Sending discover...

Sending select for 10.0.0.41...

Lease of 10.0.0.41 obtained, lease time 86400

假设出现dhcp问题能够先查看日志，重新启动dnsmasq进程。

killall dnsmasq

service neutron-dhcp-agent restart

dhcp使用的是udp协议，默认port为68和67（68port发送到67），能够

tcpdump  -n port 67 or port 68

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