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Questions tagged [dhcp]

Dynamic Host Control Protocol - automatic assignment of addresses to network devices. Questions about configuring it, blocking rogue DHCP servers, etc.

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PiHole issues with dual band routers [on hold]

I have a raspberry pi running pihole as an adblocker AND dhcp server, and a dual band router with two discrete signals send out {ssid1.2G and ssid2.5G} When the pihole dhcp service is on, my laptop (...
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Importance of DHCP option 12, client host name

The main purpose of a DHCP server is to provide dynamic configuration for a group of hosts (mainly IP, Gateway and DNS). There are several options that can also be sent. Option 12 (client hostname), ...
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1answer
39 views

Configuring DHCP on Juniper junos-vsrx-12.1X47-D20.7-domestic on vmware

I'm preparing for JNCIS-SEC exam. I used junos-vsrx-12.1X47-D20.7-domestic image to create virtual machine in order to practice for the exam. I am following this to configure the vsrx. When I do the ...
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1answer
24 views

Connectivity from DHCP-based machines to servers with static IP addresses on the same gateway

I have Comcast service with 5 static IP addresses, using a Cisco DPC3939B as the cable modem. In addition to the 5 machines with static IP addresses, there are additional devices that get their IP ...
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1answer
42 views

Can a machine be its own DHCP server for another interface?

I was wondering if a single machine (with several network interfaces) can be, at the same time, a DHCP server and a DHCP client, that is the server would dynamically attribute an IP address to an ...
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1answer
25 views

Why do Cisco IOS switches send packets to DHCP servers with zero giaddr field when DHCP snooping is on?

I recently troubleshooted a network where the switch had DHCP snooping turned on and even though the router which was acting as a DHCP server was connected to a trusted port, the client wasn't able to ...
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3answers
48 views

Sonicwall DHCP client option code

Is it possible to set DHCP option codes for the DHCP client (the WAN interface)? I am quite sure that you can send options in a DHCP request, I quote: "This option is used by DHCP clients to specify ...
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2answers
22 views

Sonicwall DHCP Reserved IPs Broken After Expanding Subnet

I've just expanded our subnet at work from /24 to /22 now that we've started running out of IPs. For ease of transition, I left all statically-assigned IPs at their original addresses and moved the ...
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0answers
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DHCP ivp6 vs DHCP ipv4 router config (cisco)

When setting up a router as dchp server in ipv4, we specify a pool under which we give the network and the default-gateway and that's it: However in ipv6 stateless dhcp , we create the pool then ...
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3answers
496 views

Basic networking and DHCP theory

Background We're organizing an event where we need to connect about 10 PCs into a single LAN network (no internet access). We've got some general experience with "home" and "web" networking but we've ...
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1answer
74 views

DHCP OFFER not reaching client through several routers and ASA [closed]

So recently we received notification from one of our remote branches that certain PCs were unable to connect to the internet. We determined that DHCP was the cause. The basic L3 path between the ...
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1answer
73 views

How VLAN devices will get automatically IP from DHCP server

I have one Windows server 2012R2 which has 10.219.1.1 IP address & I also have Cisco Catalyst 2960-X Series which is layer 2, we managed to do inter VLAN routing by updating its firmware, where we ...
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58 views

Is a dedicated DHCP server required for PXE boot? [closed]

Read a lot of posts on PXE server setup. Most of them mention to setup DHCP server. My question is even though we used a managed switch (e.g. Cisco SG-300), which comes with DHCP functionality, do we ...
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1answer
60 views

Two ip helper for two different services?

There is a vlan5 currently configured with an ip helper-address to forward the broadcast traffic to our DHCP on a different vlan. Works perfectly and everyone is happy. interface Vlan5 description ...
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1answer
366 views

Single DHCP server for multiple VLANs (packet tracer)

I have a layer 2 switch, PC 1 connected to port 1 and PC 2 connected to port 2. Port 1 is in VLAN 20 Port 2 is in VLAN 21 Can I use a single DHCP server without a router and give IP to both the PCs?...
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1answer
104 views

How to configure DHCP pools for 2 VLANs/subnets sharing a switch

I've set up DHCP pools on a layer 3 switch that goes out to 13 layer 2 switches. Most of which have their own subnet and VLANs, and everything works fine when that's the case. But when there are two ...
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2answers
38 views

Is it possible to enable DHCP on multiple hosts via Cisco switches or routers? [closed]

I think I know the answer to this, but thought I ought to ask around. When setting up new networks with multiple hosts, like a university computer lab VLAN with 30+ workstations, for instance, is it ...
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2answers
53 views

Routing DHCP into different LANS

If I had a router that's connects my 2 LANs and there is a single DHCP, in the either LAN. How and what would be my configurations for the DHCP so that it provides the IPs to both the LANS through the ...
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1answer
80 views

TCP connection question

Let’s say I have 4 ethernet interfaces getting IP addresses via DHCP. I make a TCP connection to a TCP server via one of the IP addresses on a certain ethernet interface. After the connection is ...
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1answer
75 views

Vlan cannot get DHCP address from using Router and L3 Switch

Simplified diagram of a larger network, but I'm having trouble getting DHCP from the router. Going into simulation mode in packet tracer, I'm seeing an error on the layer 3 switch saying "There is no ...
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1answer
110 views

DHCP relay on Juniper MX

Hi I got a problem with bootp relay on a juniper router(s). I got helpers bootp interface configured with: irb.10 broadcast server 10.20.1.10 server 10.20.1.11 theres several irb ...
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1answer
31 views

Static Allocation vs Dynamic Allocation [IP Addresses]

Quick question regarding static vs dynamic allocation of IP addresses. I understand that in static IP addressing the address does not change while in dynamic addressing it could differ each time a new ...
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4answers
166 views

Does a router always have two IP addresses?

So I got pretty confused with this question, and while looking online I've found several answers saying that a router does need 2 IP addresses at a minimum, but it isn't clear to me why. Lets say ...
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1answer
41 views

How Pppoe subscriber with static ip sends ipcp request

How a pppoe subscriber with static ip sends ipcp configure request. For dhcp the subscriber can include 0.0.0.0 in configure request of ipcp packet and obtain its ip from remote server. But in static ...
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1answer
67 views

What hardware do I need to assign IPs based on port?

Similar (but different) question: Assign an IP address based on switch port I regularly need to test our hardware products. Usually that consists of having ~50 devices sitting on a bench for some ...
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1answer
58 views

How a client behaves if same IP address is assigned to two different interfaces?

First of all, these questions are just out of curiosity. I don't have such configuration, I'm just wondering how a box would behave in such environment. Say we have a Linux box with two network ...
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1answer
138 views

Assign DHCP IP address on Cisco router interface

Hi, dhcp router is configured with following DHCP settings: ip dhcp pool B network 192.168.1.0 255.255.255.0 default-router 192.168.1.1 ip dhcp pool C network 192.168.2.0 255.255.255.0 default-...
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1answer
28 views

What is the use of Manual IP Settings on Copy Machine which is Connected to Router with DHCP

Today, my company got a new copy machine. During configuration, copy machine guy asked me what IP address we want to use for the copy machine. I said, "I'm gonna reserve 192.168.1.200 in DHCP ...
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3answers
132 views

Cisco 2960 not receiving dhcp from the router

I have a problem with Dhcp of some the Vlans. here is how my network is : I have a router ASR1001, which connects 15 switches(2960) as a ring topology. each switch has a subinterface of the router ...
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1answer
93 views

Help this problem with Dhcp Server with two switches

I will try to explain my problem. I am trying that Switch 1 can give dhcp for pcs but i cannot, in Switch 0 I can give dhcp server in the pcs. sorry for my bad english ROUTER ! version 15.1 no ...
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1answer
427 views

Why are DHCP ACK and REQ messages broadcast in Link Layer?

When I look at the protocol, I see that DHCP Request and Acknowledgement are both broadcast in the link layer. However at that point, both sides actually know each other's MAC addresses. Why do they ...
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1answer
889 views

“ssh: connect to host myserver port 22: Invalid argument” (intermittent, ipv6, link-local address, dhcp hostname) [closed]

Since this question is off-topic I moved it to Super User. But I was unable to delete it. Here is the new location. Here is the original question: I'm trying to connect to a headless server via my ...
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2answers
43 views

Advice on potentially needed subnet expansions

I work for a non-profit with some slightly more antiquated hardware. We have 3 locations, about 700 devices across them. Right now our locations are set up as: Location 1 (Main) - /23 with a DHCP ...
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2answers
185 views

Configure VLAN with DHCP traffic properly forwarded

I have a windows DHCP server in VLAN 10 and I have wireless clients in VLAN 288. The VLANs are defined in my Juniper EX-4600 and the VLANs are tagged/trunked all the way to the Meraki APs. [DHCP]---[...
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2answers
121 views

Should an Access Point without internet set the DHCP Offer-Router (3) option?

Wireless device (internet of things device, like wireless printer) creates a wifi network. The device has ip 10.0.0.1 and does not have acces to the internet. The DHCP server on the device sets the ...
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1answer
114 views

Why would my router send an ARP request about a device that's already listed in its ARP cache?

I checked my Ubiquiti EdgeRouterX's ARP table and my laptop IP and MAC address were there. I then checked the DHCP lease and my laptop's IP address doesn't expire until tomorrow. I then ran ...
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2answers
113 views

Does DHCP Client or Server re assigns the IP address?

I know that DHCP protocol ensures that they don't assign an address which is already assigned to another host. This can be true even when the host has been assigned with a static IP address. Also, ...
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2answers
308 views

Why DHCP protocol needs Client ID?

A DHCP request from multiple hosts can be differentiated using Src Mac Address. So, why do need DHCP client ID to differentiate the DHCP request. I understand that they need some IP address because ...
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3answers
68 views

Pinging computer on a local wireless network, what exactly happens?

I'm trying to get a better understanding of networking in general. Here's one of the many questions I got: What exactly happens (network wise) when I ping 192.168.0.5 from 192.168.0.3, when both are ...
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1answer
378 views

Can a VLAN have hosts with IP addresses outside it Subnet IP range scope?

I have 3 entities in my network. A server,switch and an appliance which acts as a DHCP/PXE server. When the server starts up, the DHCP server has to PXE boot the server. A seperate VLAN(1234) is ...
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1answer
32 views

Discovering public ip from wifi signals, shodan, parent router NAT [closed]

MAC addresses innately do not change right? and you're able to scan for broadcasting APs where you'll be able to detect different nearby mac addresses of each AP.. Public IP addresses change, ...
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2answers
59 views

DHCP client on Cisco 6509-E?

I'd like to have a Cisco 6509-E join a VLAN as a client so I can add some reachability SLAs across an organizational boundary. I've tried doing the usual "ip address dhcp" on an actual interface as ...
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1answer
393 views

Unifi USG gateway

On my firewall "gate protect", I have set one network to use DHCP with the subnet 172.25.112.0/24. After I connect it on my USG pro as WAN and the LAN port goes on the ubnt POE switch there is ...
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4answers
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What is the difference between DHCP and NAT?

Both seem the same to me. I don't see how DHCP is different from Dynamic NAT. Can anyone please help?
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2answers
183 views

DHCP relay binding

As per my knowledge, the Relay agent does the job of forwarding the DHCPDISCOVER and DHCPREQUEST from the Client to the Server and DHCPOFFER and DHCPACK from the Server to the Client. But it not ...
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60 views

Dhcp server not working after server bootup when plugged into managed switch

I have very simple network with one DHCP pool. I've installed ISC dhcp on ubuntu linux and everything works fine and fast on simple unmanaged switch. After connect server to managed switch TP-Link ...
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1answer
243 views

Use DHCP relay address as default gateway when no router option (3) included? [closed]

When I connect my custom embedded device to my network the DHCP responses do not include the router option (3). In this case should the device use the DHCP server ip address as the default gateway? My ...
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1answer
190 views

GNS3 IP helper in Multiple Vlans

Good day everyone, I'am having trouble getting VPCs from VLAN 3 to communicate with the DHCP on Vlan 3 I've also tried configured IP helper on the Router but to no avail. Router Configuration dump ...
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1answer
102 views

DHCP Relay Problem

I'm trying to get DHCP to work between these two Devices. Any tip's would be wonderful! Switch Config Switch#show run Building configuration... Current configuration : 1596 bytes ! ! Last ...
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0answers
54 views

DHCP Requests not coming through [closed]

I've currently got a network issue that is preventing clients connecting to a guest WiFi network from getting an IP address via DHCP. I've been re-configuring and tweaking setting for the last few ...