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IP Address Not Allocated To Instance by DHCP

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Problem

  • Instance fails to receive IP address from the DHCP server after a reboot.

  • Packet capture on the tap device of the instance and the bond0 interface shows the Broadcast Request is leaving the tap device but no packets are seen on the bond0 interface.

$ sudo tcpdump -nnei tapf6715be8-f9
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on tapf6715be8-f9, link-type EN10MB (Ethernet), capture size 262144 bytes
fa:16:3e:24:98:2b > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from fa:16:3e:24:98:2b, length 300
fa:16:3e:24:98:2b > 33:33:00:01:00:02, ethertype IPv6 (0x86dd), length 157: fe80::ec0c:f912:fd0a:e575.546 > ff02::1:2.547: dhcp6 solicit
fa:16:3e:24:98:2b > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from fa:16:3e:24:98:2b, length 300

  • Packet capture on bond0 interface.

$ sudo tcpdump -nnei bond0 ether host fa:16:3e:24:98:2b
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on bond0, link-type EN10MB (Ethernet), capture size 262144 bytes

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Environment

  • Platform9 Managed OpenStack - v3.6.0 and Higher

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Cause

There is no physical interface connected to the Bridge br-vlan.

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Resolution

  1. Add the interface (bond 0) to the bridge (br-vlan).

  1. After adding the interface, force the instance to renew the IP address from DHCP.

  1. Following is the packet capture of the instance on the tap device and we can see that the DORA process for DHCP completed successfully.

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