![]() non call processing services) to the cluster and its endpoints. Depending on the size of your deployment, you may have this service running on the Publisher node or multiple nodes dedicated to providing supplementary services (i.e. Giaddr helps the DHCP server to find the correct address pool for granting the address.The Cisco Unified Communications (CUCM) solution architecture has a TFTP service that you enable on one or more servers in a given cluster. The packet is sent directly to the IP of the server located somewhere in the routable IP cloud. In such solution, DHCP discover packets typically getting to the default gateway interface are transformed into unicast packets (DHCP discover embedded message) with giaddr field that tells the server about logical attachment identification. Right trace! But for the sake of DHCP scalability there is an option to have a DHCP server outside the subnet. You can ask yourself if there is a need for having a DHCP server in the same L2 segment (VLAN), because the DHCP OFFER message relies on the broadcast destination address which is good for the same subnet only. ![]() What if DHCP server is not in the same subnet ? Almost all DHCP server vendors are able to pass DHCP options. In addition to necessary DHCP parameters, there are DHCP options like popular Option 150 used in IP Telephony to inform IP Phones about the IP address of IP PBX for proper phone registration – for example Cisco Call Manager or Asterisk PBX. However, in real-world scenarios, most of the communication goes beyond the subnet and relies on Fully Qualified Domain Names (FQDN). Using only IP addresses for communication also eliminates the need of name translations so DNS is still optional. This way there is no need for going beyond our own subnet and that’s why a gateway is not needed. ![]() This is true in a scenario the device is within the same subnet as other devices and communicates with others knowing their IP addresses. ![]() In theory, only an IP address and mask are needed for the device to work. What information getting from DHCP protocol are necessary and which are optional? Enterprise Wireless: Cisco Products Overview. ![]()
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