Object Management API (OMAPI)
The Object Management API is an interface on the ISC DHCP server. It provides access to the objects (leases, hosts or groups) stored in its database.
History
The API was introduced by the ISC in version 3 of the DHCP software.
Protocol dependencies
TCP: Typically, OMAPI uses TCP as its transport protocol. The well known TCP port for OMAPI traffic is 7911.
Example traffic
Frame 755 (129 bytes on wire, 129 bytes captured) Ethernet II, Src: Intel_bf:3b:59 (00:90:27:bf:3b:59), Dst: Cisco_f2:03:78 (00:d0:bc:f2:03:78) Internet Protocol, Src: 192.168.21.229 (192.168.21.229), Dst: 192.168.1.251 (192.168.1.251) Transmission Control Protocol, Src Port: 33156 (33156), Dst Port: 7911 (7911), Seq: 3915, Ack: 12060, Len: 63 ISC Object Management API, Opcode: Open Authentication ID: 0 Authentication length: 0 Opcode: Open (1) Handle: 0 ID: 1804289445 Response ID: 0 Message name length: 4 Message name: type Message value length: 5 Message value: lease Message end tag Object name length: 10 Object name: ip-address Object value length: 4 Object value: C0A8093F Message end tag
Wireshark
The OMAPI dissector is fully functional.
Preference Settings
There are no preferences for this protocol dissector
Example capture file
Display Filter
A complete list of OMAPI display filter fields can be found in the display filter reference
Show only the OMAPI based traffic:
omapi
Capture Filter
You cannot directly filter OMAPI protocols while capturing. However, if you know the TCP port used (see above), you can filter on that one.
Capture only the OMAPI traffic over the default port (7911):
tcp port 7911
External links
DHCP source code - contains api+protocol description.
man omapi - A OMAPI man page.
man omshell - The simple CLI interface for OMAPI.