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Requests are on UDP reversed port 68

&

Server replies on UDP reversed port 67

If the above is right, then you can allow those ports on Linux(Ubuntu) with:

sudo iptables -A OUTPUT -p udp --dport 68 -j ACCEPT

sudo iptables -A INPUT -p udp --dport 67 -j ACCEPT

Oh and don't forget to erase the password timestamp:

sudo -k

Further info in "man sudo"

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Q: What ports are used by DHCP and the DHCP clients?
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What ports are used by dhcp and the DHCP client?

The port 67 and port 68 are used by DHCP and the DHCP clients.


What technology automatically assigns addresses to clients?

DHCP (Dynamic Host Configuration Protocol) assigns IP Addresses & other DHCP Options to Clients.


What is the use of a DHCP relay agent?

The use of a DHCP relay agent is an agent that relays DHCP between DHCP clients and DHCP servers on different IP networks. The DHCP relay agent is compliant with RFC 1542.


What are User Classes and Vendor Classes in DHCP?

http://support.microsoft.com/kb/266675 The following list contains pre-defined vendor classes that are available in Windows 2000 DHCP server. Collapse this tableExpand this table {| ! Class Data ! Class Name ! Description | MSFT 5.0 Microsoft Windows 2000 options Class that includes all Windows 2000 DHCP clients. MSFT 98 Microsoft Windows 98 options Class that includes all Windows 98 and Microsoft Windows Millennium Edition (Me) DHCP clients. MSFT Microsoft options Class that includes all Windows 98, Windows Me, and Windows 2000 DHCP clients. |} If you have non-Microsoft DHCP clients, you can define other vendor-specific classes on the DHCP server. When you define such classes, make sure the vendor class identifier that you define matches the identifier used by the clients. Back to the top The following list contains pre-defined user classes that are available in Windows 2000 DHCP server. Collapse this tableExpand this table {| ! Class ID ! Class Type ! Description | Unspecified Default user class All DHCP clients that have no user class specified. RRAS.Microsoft Default Routing and Remote Access class All Dial-Up Networking (DUN) clients. Bootp Default Bootp class All Bootp clients |} In addition to these pre-defined classes, you can also add custom user classes for Windows 2000 DHCP clients. When you configure such classes, you must specify a custom identifier that corresponds to the user class defined on the DHCP server. For additional information about how to create other user and vendor classes, click the article number below to view the article in the Microsoft Knowledge Base:


How would you describe the DHCP leasing process?

FROM MSDNDHCP Lease ProcessA DHCP-enabled client obtains a lease for an IP address from a DHCP server. Before the lease expires, the DHCP server must renew the lease for the client or the client must obtain a new lease. Leases are retained in the DHCP server database approximately one day after expiration. This grace period protects a client's lease in case the client and server are in different time zones, their internal clocks are not synchronized, or the client is off the network when the lease expires.The DHCP lease process is a process that occurs when a computer which is a DHCP client initially boots up on the network, to provide an IP address and any additional TCP/IP configuration parameters to these clients.The terminology and concepts used when discussing DHCP leasing or the DHCP lease process is summarized below:DHCP lease: This is the amount of time for which a DHCP client is allowed to make use of a specific IP addresses. The default setting for the DHCP lease is 8 days.DHCP lease process: The process which occurs when the client initially boots up on the network. The DHCP lease process enables DHCP clients to automatically obtain IP addresses from a DHCP server.DHCP Discovery Broadcast message: This is a message sent over the network by a client computer that wants to obtain an IP address from a DHCP server.DHCP Offer message: This is message sent by DHCP servers that serves as a reply to a Discovery Broadcast message.DHCP Request Broadcast message: This message indicates that the client accepted an IP address offer from the first DHCP server which responded to it. The client broadcasts this particular message so that all the other DHCP servers that offered addresses to the client can withdraw their IP addresses.DHCP Acknowledge message: This message is sent by the DHCP server to the DHCP client, and is the process whereby which the IP address lease is assigned to the client.Unlimited lease duration: If you do not want the IP address assigned for a particular client to expire, you assign an unlimited lease duration.DHCP scopes: A scope can be defined as a set of IP addresses which the DHCP server can allocate or assign to DHCP clients. A scope contains specific configuration information for clients that have IP addresses which are within a particular scope. Scope information for each DHCP server is specific to that particular DHCP server only, and is not shared between DHCP servers. During the DHCP lease process, the DHCP scopes configured for a DHCP server is used to provide a DHCP client with an IP address.You can configure different lease duration settings for each DHCP scope.The lease duration rules which should be implemented when you determine the lease duration time for the scope of each of your subnets are:Use a shorter lease duration time if you have numerous mobile users, and if you are working in an environment that constantly has configuration changes.Use a longer lease duration time if the following statements are true:There are no mobile computersThe environment does not continually experience configuration changesIncrease the default setting of 8 days if the number of IP addresses for each subnet is by far greater than the number of DHCP devices within your environment.Use a shorter lease duration period if you have a limited number of IP addresses for each subnet, and you are near to meeting limit.Understanding the DHCP Lease ProcessThe DHCP lease process is a four-step process that occurs when a DHCP client initially boots up on the network. The DHCP process remains unchanged since its initial introduction with Windows NT 4.0. During the DHCP lease process, negotiation for an IP address occurs between a DHCP server and a client that needs to obtain an IP address. In a TCP/IP based network, to uniquely identify computers on the network, each computer must have a unique IP address. To communicate on the Internet and private TCP/IP network, all hosts defined on the network must have IP addresses. The 32-bit IP address identifies a particular host on the network. With DHCP, the system assigns IP addresses to clients, which in turn leads to less incorrect configurations of IP addresses. This is mainly due to IP configuration information being entered at one location, and the server distributing this information to clients. Duplicated IP addresses are also prevented.The DHCP lease process that occurs between the DHCP server and client is a simple process. The negotiation process for an IP address consists of four messages sent between the DHCP server and the DHCP client.Two messages from the clientTwo messages from the DHCP serverWhen the server assigns IP addresses to DHCP clients, it starts allocating addresses commencing from the bottom of its scope range, and starts moving to the top of its scope range.All unused addresses have to be used before the DHCP server:Allocates a previously used IP addresses to a new DHCP client. The DHCP server first assigns IP addresses that have not been used for the longest amount of time prior to assigning other previously used IP addresses.Allocates an expired IP addresses to a new DHCP clientDuring the four-step DHCP lease process, the events that occur are defined by the types of DHCP messages which are exchanged between the DHCP server and DHCP client:DHCPDISCOVER message: This message is used to request an IP address lease from a DHCP server. The message is sent when the client boots up on the network. The message is sent as a broadcast packet over the network, requesting for a DHCP server to respond to itDHCPOFFER message: This message is a response to a DHCPDISCOVER message, and is sent by one or numerous DHCP servers.DHCPREQUEST message: The client sends the initial DHCP server which responded to its request a DHCP Request message. The message basically indicates that the client is requesting the particular IP address for lease. The other DHCP servers who offered addresses withdraw those addresses at this point.DHCPACK message: The DHCP Acknowledge message is sent by the DHCP server to the DHCP client and is the process whereby which the DHCP server assigns the IP address lease to the DHCP client.The four steps involved in the DHCP lease process is often called DORA:DiscoverOfferRequestAcknowledge

Related questions

What ports are used by dhcp and the DHCP client?

The port 67 and port 68 are used by DHCP and the DHCP clients.


Does the dhcp server have to be activated to issue leases to dhcp clients?

dhcp has to be authorized


What technology automatically assigns addresses to clients?

DHCP (Dynamic Host Configuration Protocol) assigns IP Addresses & other DHCP Options to Clients.


What is server in networking?

Server is a system that is used for providing services to clients. for example print server provides print service, dhcp service provides dhcp service


Which type of DHCP packet is used by servers to acknowledge a clients acceptance of an offered IP address?

DHCPACK


What technology automatically assigns IPA addresses to clients?

DHCP (Dynamic Host Configuration Protocol) assigns IP Addresses & other DHCP Options to Clients.


Configure the dhcp clients to retrieve dynamic ip addresses from dhcp server?

Just make sure you set the clients to "automatically receive IP Addresses".


What is the use of a DHCP relay agent?

The use of a DHCP relay agent is an agent that relays DHCP between DHCP clients and DHCP servers on different IP networks. The DHCP relay agent is compliant with RFC 1542.


What does dhcp use to determine if a dhcp client has an ip reservation?

DHCP uses the clients MAC address to determine the IP address a client receives.


What is the best description of a dhcp?

it assigns IP address to clients


Which statements describe how DHCP clients will be affected by the abscence of DHCP server during boot?

D. You didn't list answers.


What is dhcp configuration?

DHCP stands for Dynamic host configuration protocol. DHCP is a piece of the TCP/IP protocol suite that handles the automatic assignment of IP addresses to clients.