Questions tagged [dhcp]

For questions about DHCP in in relation to network devices. For instance, you are setting up DHCP on a layer 3 switch.

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DHCP Discover Broadcast and its IP (255.255.255) [duplicate]

Cheers, I am trying to learn more about DHCP, and when studying about the session that DHCP goes through every one mentions that it broadcasts a discover message at IP: (255.255.255.255) (as seen here ...
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How to configure a router as a dhcp server for vlans throught a Layer 3 switch?

I would like to know what commands to type in the different switches and the router to to make the router function as a dhcp server for each PC in seperate vlans . I know to create the dhcp pools in ...
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What could be the bottleneck of my load-testing case?

I need to bring up a bunch of my devices in the network to hit some other service, for testing purposes. And I have used GNS3 to simulate that. As you may find in my GNS3 project, I have such ...
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Question about subinterface DHCP relay CISCO

I want to make 4 PC got DHCP IP address No problem with left side, but right side 2 PC can't get IP automaitic. I think the problem is DHCP Relay. How can I use ip helper-address for subinterface of ...
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Is there an equivalent of the Cisco/ Cisco esque command "ip helper-address a.b.c.d" on Mellanox switches?

Apologies for my newbie question. I have recently had a Mellanox switch added to the mix. I was using an "IP helper-address" to forward DHCP requests in different VLANs to my DHCP server(s) ...
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How does DHCP work?

I'm carrying out an experiment to test the mechanism behind DHCP. In this topology, I disable the link between the switch and the router. However, the computer still request IP address successfully. ...
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How does a DHCP server know which network interface and subnet the new IP address should be on

I've read that DHCP servers add a column to your iptable in your router. A new dynamically created IP address with a network interface and a subnet mask. Then the IP address is matched with your MAC ...
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How can u assign IP addressing for point to multipoint switches that connect to only one router?

I was wondering if I can assign two network address in a LAN while the switches are point to multipoint which connect to only one router. How will me DHCP going? Router - Switch 1 - Switch 2,3,4
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how to configure dnsmasq client-identifier for juniper prefix host-name

I have a Juniper switch that has a dhcp-client configured like this: show interfaces irb unit 0 family inet dhcp client-identifier { prefix { host-name; } } I ...
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Apply Interface Default Gateway to Entire Device

I feel there may be a very simple term for what I trying to do, but I'm not sure what it is, and it is difficult to search for it in concise words. The shortest description I can come up with: "I ...
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Configuration of DHCP for multiple vlans

I have the following network on Packet Tracer. The hosts are in different vlans each one. My goal is that the DHCP server can give IP to the hosts. Here is what I made for each vlan (the example is ...
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Do IPv6 addresses have better persistence with DHCPv6?

I have a LAN with about 25 devices that occasionally grab each other's IP address via DHCPv4. I know there are certain lease time limits and it can be set to very long periods to work it around to an ...
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2 answers
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IRDP protocol nowadays

I'm considering to remove rdisc tool from iputils project (see https://github.com/iputils/iputils/issues/363). This tool implements ICMP Internet Router Discovery Protocol (IRDP). Is IRDP really ...
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Configure dhcp relay agent and router on stick

I need help. I don't know what i did wrong because i have configured the dhcp pool, subinterfaces and dhcp relay agent. Gateway pc uses static ip address while Branch pc acquired their ip address ...
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Assigning static IPs to VoIP phones in packet tracer

Is there a way to assign IPs and dn to VoIP phones in a network configuration without using DHCP? Such that if I have PCs and VoIP phones connected to the same switch, which is connected to a router ...
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How to add two VLANs for DHCP Pool

Currently one of my customer has DHCP pool created in Cisco Switch and ip address range is 192.168.25.0/24 (This is a VLAN). Now they have 230 devices and They are going to increase device count by ...
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Assigning static IP address from the DHCP pool range on Cisco 800 series

What happens if I assign a static IP address to a device in a LAN where there is an active DHCP server and the address falls within the configured DHCP pool and DHCP server is Cisco 800 Series? Most ...
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Cisco DHCP using dynamic updates

I would like to use a configuration on a Cisco router that allows for clients to resolve the names of other clients without the use of mDNS. I have following configuration: roTST01#show running-config ...
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Cisco IOS - Delay DHCP offers

I have two routers in the same subnet that have a HSRP configuration in order to take over, if one of the device fails. There is the same DHCP configuration on both devices: ip dhcp pool LAN network ...
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Communication between subnets on Sonicwall firewall

I have a Sonicwall TZ-350. X0 is the default LAN with IP 192.168.10.1, and X1 is the WAN. I've set up a second local subnet on X2 with IP 192.168.20.1 for a single NAS device (no switch; the device is ...
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DHCP Packet Drops on Return

The DHCP packet makes it from the Security computer all the way to the DHCP server and back to Router1 but gets stuck there. All all packets make it across when the device has a static ip assigned. ...
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Does an IPv4 DHCP Relay Agent care about Option 80 (rapid-commit)

I'm trying to figure out if an IPv4 DHCP Relay Agent needs to care about a rapid-commit (Option 80) included in a DHCP Discover. My understanding is that the Relay Agent is supposed to simply converts ...
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How does a device receive default gateway IP address?

When and how does a device get information about default gateway in LAN? I know you can define default gateway statically, but which protocol is used when it is not statically defined? Is it from ...
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DHCP Help 3560-CX + Aruba AP515

The problem VLAN 100 is not assigning IP address to the SSID Guest from the AP, but Aruba is Tagging the SSID to be VLAN 100. How do I get the Switch to assign the DHCP? On the switch, it seems to ...
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Arp Access-List Without An Interface [duplicate]

I have dhcp snooping an arp inspection setup on my VLAN. I have a number of clients that need to be statically set on this VLAN but still plug into a DHCP access port on the VLAN. I have ip dhcp ...
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IP Snooping\ARP Inspection With Static Devices On DHCP VLAN

Consider this network: I have enabled DHCP snooping on my system. Switch A has the DHCP connected and the port on VLAN 70 for DHCP has been trusted to allow for reading the database and passing ...
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How does Network Layer behave when client received a unicast DHCP offer?

I went through various stack exchange post to understand the concept of DHCP offer when it comes as a unicast to client from the DHCP server. A server can send a unicast DHCP offer since it knows the ...
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Is it possible to configure DHCP on a router or UTM firewall for the multiple VLANs on L3 Switch?

I'm working on expanding our office network to accommodate more users/devices. Currently we have the DHCP configured on a UTM firewall(cyberoam ing50) device(cum router) providing IP addresses for ...
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1941W wireless clients losing DHCP IP address [closed]

I am attempting to 'extend' a 192.168.1.0\24 network with an experimental network 192.168.10.0\24 using a 1941W router. I have configured 1941W to distribute a 192.168.10.0\24 network, with WLAN ...
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Cisco IOS Software [Everest], ISR 4331. Vlan+Vrf+Dhcp

I'm looking after to use a setup with that objectives in mind: Create a subinterface on interface GigabitEthernet0/0/1 create a Vlan and assign it to that subinterface create a vrrf and assign it to ...
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Cisco ip helper-address

I am looking at the DHCP documentation and i cannot seam to find how to configure the router to use a loopback interface as the relay-agent. My objective is to use option 82 so that the dhcp server is ...
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Per-VLAN DHCP pools on the switch

Let us say I have a switch on which I have created two VLANs 10 and 20. I have set ports 1-10 to be on VLAN 10 and ports 11-20 to be on VLAN 20. Presently the PCs in both VLANs are configured with ...
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2 votes
2 answers
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General: What is a dynamic gateway, how does it work, where is it used?

I saw this option in my OPNsense gateway configuration, and was hoping someone could shed light on what it is, exactly: Dynamic gateway policy: [YES/NO] This interface does not require an ...
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Are new DHCP options sent automatically to clients?

When new DHCP options are configured on a DHCP server (Like NTP and DNS server options) are these sent out to clients automatically? if clients were provided an infinite lease time and so they would ...
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4 answers
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How the device chooses between multiple DHCP pools?

In a router , you can create and configure multiple DHCP pools each one with its own default route and dns server . And because the DHCP pool configuration is not specific to an interface in a router, ...
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Cisco 2960-CX - Dynamic Management IP over trunk link

I have a Cisco 2960-CX switch mounted in a Mobile CT (hospital owned). This "trailer" moves between my 7 campuses as needed. Is there a way for the switch to obtain an IP address ...
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Question about the rebooting state of the DHCP protocol [closed]

Taking into account this diagram... I wonder if a device, after a reboot having a previous known configuration, uses it from the start even tho it's still asking to check if it can continue using ...
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3 answers
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how to capture DHCP packets in wireshark

Hy! I want to capture DHCP packets in Wireshark but I did not receive any. Not my filter wrong, I don't get any. So I think I can't trigger the DHCP communications. my filters: dhcp bootp udp.port == ...
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Will devices with static addresses, will be disconnected when DHCP Server is changed?

In my office network, the DCHP Server is set to 192.168.0.1/24. I want to increase the available pool, so I am thinking update the above setting to 192.168.0.1/23 in order to have: Network: 192.168....
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Best practice / advice for cisco 3560 behind Virtualised OPNsense

Currently I run the below scheme. The problem is that when ESXi is down it takes down all the network with it, so I have to boot up another router to log in to it. WAN > OPNsense (in ESXi)> ...
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Some mobile clients are unable to connect to UniFi AP mysteriously

We have two UniFi Controllers, one contains the main internet its directly connected to the fibre and then we give internet to the second controller using LAN connection, internet works fine in main ...
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Juniper / SRX-100 / Repurpose old device / Disable DHCP?

I have an old Juniper SRX-100. I want to re-purpose it for my network. I need to extend the network in a new location, so I need more ports. I could use a simple switch, but I have this laying ...
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Why we define pool for declaring CISCO router DHCP?

In case declaring DHCP server in CISCO routers, should define pool with network addresses.↓ Example Router(config)#ip dhcp pool net1 Router(dhcp-config)#network 192.168.1.0 255.255.255.0 The router ...
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Security issues with DHCP snooping on cascading switches

Consider the following topology: This image was copied from here and in this article it specifies the following: Remember that port Fa0/24 on SW2 is an untrusted port from DHCP Snooping’s point of ...
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Assigning IP addresses to multiple switches

Thank you in advance for taking the time to read my question, i appreciate it. I am in need of help on IP assigning to 4 brand NEW Araknis switches that I am replacing with the current netgear/tp-link ...
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2 votes
1 answer
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Why can my device not get an ip from DHCP in a network with 2 VLANS of which one has DHCP?

In our company we have a CISCO 2811 Switch accompanied by an HP1920 Switch. Our current configuration consists of 2 VLANS: VLAN-2 that has no DHCP in IP range 192.168.0.0/24 VLAN-5 That contains DHCP ...
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Why DHCP client doesn't issue a DHCPREQUEST as it has received a DHCPOFFER?

In GNS3 (and using Cisco routers), I've created four subnetworks like the following: The goal is to set up a DHCP server on router R1 and a DHCP relay agent on router R2 in order to make it available ...
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Simplest way to achieve single IP communication with IP camera and simple MCU?

I have a product that uses an IP camera and a simple ATmega-based motherboard for general I/O control, managing a very simple web interface, etc. Ideally, I would like to be able to access both of ...
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Cisco DHCP relay with Microsoft DHCP server

Current situation: we have a C3850 switch serving DHCP lease to desktop clients without communicating with any upstream DHCP server Objective: We would like the C3850 switch continue to serve DHCP ...
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Unknown DHCP problem

Sometimes in my network I have some DHCP problem, the clients don't receive their IP. The problem seems connected with the switch because, for example, if I change the switch port of the client the ...
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