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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Full Network Enumeration without an IP address [closed]

I've faced a situation where I connected to a network with an ethernet cable and the DHCP server was disabled, so I didn't get an assigned ip. I was wondering if I can run a scan with kali linux tools ...
IsmailBarrous's user avatar
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Juniper and EdgeCore dhcpv6-relay remote-id (option 37)

I have the following problem. I have minimal configuration of dhcpv6-relay agent on QFX5100. Before the QFX, there is an Edgecore switch on which DHCPv6 snooping is enabled. The problem occurs as soon ...
Libor's user avatar
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How is routing precedence determined in DHCP Offer and Acknowledgement packet from server?

I'm learning about the DORA process in TCP IP. And the way server communicates with client is very "confusing" to me. Let's take an example of DHCP Offer: At this point, the client is still ...
barnyard9's user avatar
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DORA process TCPIP [duplicate]

http://www.tcpipguide.com/free/t_DHCPGeneralOperationandClientFiniteStateMachine.htm I'm reading through the entire Discover, Offer, Request, Acknowledgement phases in DHCP. And I am really confused. ...
barnyard9's user avatar
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Cisco catalyst 6500 not assigning static dhcp assignments to a couple of devices

in the following question cisco catalyst 6500 not honoring static ip assignments I had been able to get 16 out of the 20 devices im working with to honor the static ip settings. 4 devices are for ...
Kendrick's user avatar
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cisco catalyst 6500 not honoring static ip assignments

I have a catalyst 6500 sup720 running 15.1(2)sy6 and i have attempted to have a set of mac addresses to get a specific ip from dhcp. below is what shows on the bindings. 10.1.4.200 01e0.508b....
Kendrick's user avatar
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DHCP packets in a Wi-Fi network (WEP2-Personal)

The DHCP packets with the message type Discover, Offer, Request and Acknowledge use the L2 broadcast address for communication (even in the Acknowledge packet which has an IP destination of the newly ...
Strategist's user avatar
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ASA 5555 loses internet connectivity every few days, problem resolves by re-enabling DHCP on wan interface

I'm having a weird problem with my ASA. Every few days the internet connectivity fails (f.e. cannot ping wan ip addresses from the ASA). Problem resolves by forcibly rebinding the DHCP by no ip ...
The amateur programmer's user avatar
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1 answer
92 views

Cannot get my servers on the same broadcast domain as backbone gateway using Aruba switches

My supervisor told me to go to the server room and connect a bunch of servers to the Department network so they are accessible from office PCs. In the server room we have 7 servers, a couple of wall ...
Amjal's user avatar
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224 views

DHCP Client Traffic not going through IRB interface as expected

I have several Juniper EX4300 series switches that I'm trying to configure to meet the following specifications: I'd like each switch to manage a /24 DHCP pool that corresponds to a rack I'd like ...
Suever's user avatar
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DHCP - General relativity

The following image shows a visualization of the DHCP server in action. DHCP servers send a DHCPNACK message in a scenario where the same ip address is trying to be assigned to 2 devices. Is this ...
Forgotten Semicolon's user avatar
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DHCP request for multiple IPs at once [closed]

In DHCP, a DHCP client and a DHCP server go through the protocol exchange (DISCOVER, OFFER, REQUEST, ACK) so that the client ends up with an IP address allocated to it that is also tracked in the ...
Arun's user avatar
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Dhp L2TP reservation on cisco 1921

I use a Cisco 1921 as L2TP server. (I don't want to use RADIUS authentication.) Please is someone can tell me how is it possible to do IP reservation, using client identification? I have tried dhcp ...
JimmyConnor97's user avatar
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665 views

CISCO 9800-L Controller internal dhcp not working - GUEST WIFI

I have been trying to configure a guest network for my Cisco Catalyst 9800-L Wireless Controller for some days now. For the guest network, i want it to use an internal dhcp on the controller. I have ...
Amarnauth Persaud's user avatar
2 votes
1 answer
88 views

bandwidth on WAN link

I would like to understand how a router is able to divide bandwidth among users who are using the same WAN link.
user10388's user avatar
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No access to internet via DHCP, but works with manual IPs

My DHCP server was giving out IPs in the range 10.0.0.1/24, but I ran out of usable IPs, so I changed the subnet to 10.0.1/21 to have more available addresses, however I am now having a weird problem: ...
Mike's user avatar
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IPSec over L2GRE scenario

I wanted to know if this is a valid scenario and if it is possible to implement. There is a remote site A. and a Data center site B. Both A and B have a edge router which runs an IPSec tunnel. An ...
RootPhoenix's user avatar
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1 answer
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Does this DHCP Server need a trusted ARP Inspection port in IOS?

The switch runs Cisco IOS. You want to configure security on Switch 1. The objective is configuring Dynamic ARP Inspection on Switch 1. Which Ports or port will you configure as Trusted? A) None of ...
Atheesh Thirumalairajan's user avatar
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1 answer
559 views

HSRP and DHCP problem

I have 2 layer 3 switches DS1 and DS2. There are the same VLANs but different IP addresses on VLAN interfaces. On DS1: VLAN 10: 192.168.10.1/24 VLAN 20: 192.168.20.1/24 On DS2: VLAN 10: 192.168.10.2/...
Gekko's user avatar
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Do Directly Connected Routers Need Routing Protocols For DHCP Relay To Work?

Let us say that we have R01, R02, and R03 connected to each other, and each of them is connected to a different subnet SUB01, SUB02, and SUB03, respectively. R03 is set up as a DHCP server, and DHCP ...
Shadi's user avatar
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can a layer 2 switch block dhcp from 1 port, both in and out?

Here's what I want to do: "Wall" is the dhcp server from the ISP. "R" is my internal router. "L2" is a hypothetical switch. "fs" is my dhcp server. I want ...
user3303210's user avatar
1 vote
1 answer
74 views

CISCO cellular Router cannot reach network via my PC

I configured the cellular and my router is connected to the internet ping (5/5) Success but I still cannot access the internet via PC Here is my running-conf Current configuration : 2271 bytes ! ! ...
breka's user avatar
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1 answer
501 views

What does 'CPE' stand for, and what is it?

In reading up on NextDNS, I came across the add-cpe-id option to dnsmasq: --add-cpe-id= Add an arbitrary identifying string to DNS queries which are forwarded upstream. NextDNS uses this for your '...
OJFord's user avatar
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4 votes
2 answers
386 views

Which device gets the helper-address?

Brand new to networking and trying different scenarios. PC2 can successfully send packets to PC1 and the DHCP server if a static address is assigned. However, PC2 will not obtain a DHCP address from ...
prosportal's user avatar
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1 answer
347 views

Cisco Switch vIOS-L2 in GNS3 and CCNA 200-301

I am reading a preparation book for the CCNA Test 200-301. Currently, I am reading a section about DHCP and VLAN interfaces in a switch. The book shows an example of configuring this. switch# ...
Diego Velasco's user avatar
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1 answer
63 views

Inconsistent behavior of show ip dhcp pool poolname

show ip dhcp pool Mitarbeiter10 gives the following output: R1#show ip dhcp pool Mitarbeiter10 Pool Mitarbeiter10 : Utilization mark (high/low) : 100 / 0 Subnet size (first/next) : 0 / 0 ...
Rubus's user avatar
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1 vote
1 answer
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How do I configure a Cisco router to relay DHCP packets to DHCP server on the basis of different VLAN?

Running-Config of RO1 ! interface GigabitEthernet0/0 ip address 192.168.25.26 255.255.255.0 duplex auto speed auto ! interface GigabitEthernet0/1 no ip address duplex auto speed auto ! interface ...
Billi Sheikh's user avatar
1 vote
1 answer
289 views

UniFi6 LR access points go into scan loop [closed]

I have a Ubiquiti setup with four Unifi 6LR access points. I manage to adopt them in the controller just fine and I do briefly see the wifi come up, but then it immediately drops. SSH'ing into the ...
Keno Fischer's user avatar
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1 answer
281 views

Trusted and Untrusted ports in DHCP Snooping / ARP Inspection

From a networking course I am following, I've learned that in D. ARP Inspection, ports connected to routers or to other switches should be configured as trusted while the user ports should remain ...
Mitrixsen's user avatar
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0 votes
1 answer
653 views

Why my PCs can't get dynamic IPs from DHCP Server?

In Cisco Packet Tracer I created following network Following is how I configured the DHCP Server But the computers can't get IP addresses - getting "DHCP failed" message. Why? Please ...
DotNet Developer's user avatar
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1 answer
121 views

How to correctly setup a DHCP server in the following network?

So, I've got the following Network Configuration: Assume that, on the graph, "PCs" can be any device that needs an IP(apart from a router). Now, as explained on my title, I want to run a ...
Costas M's user avatar
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3 answers
373 views

Lost the Static IP/network settings of a device

We have a physical device (lab instrument) that we can only connect to via ethernet. Unfortunately a static IP was set with network settings and these settings has been lost. We connected our computer ...
Stan's user avatar
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1 vote
1 answer
93 views

DHCP RELAY AGENT NOT WORKING TO USER(apipa failed)

can someone help me to solved my router 1 as relay agent dhcp.Currently user 5 that connect from switch 1 is not being able to get dhcp ip address. My router 2 as dhcp server pool and user 3 ,4 is ...
Nurul Ain's user avatar
1 vote
4 answers
3k views

Can a router provide DHCP to multiple subnets that are connected via switches?

I'm trying to understand if it is possible to have a router (as shown in the below diagram) provide DHCP leases to more than one subnet if the subnets are not directly attached. If both the printers ...
NULLZ's user avatar
  • 111
3 votes
2 answers
3k views

Is DHCP in the application layer or the network layer?

Tanenbaum's Computer Networks says: 5.6 THE NETWORK LAYER IN THE INTERNET ... 5.6.4 Internet Control Protocols In addition to IP, which is used for data transfer, the Internet has several companion ...
Tim's user avatar
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0 votes
1 answer
280 views

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 ...
average_discrete_math_enjoyer's user avatar
2 votes
2 answers
1k views

How to configure a router as a dhcp server for vlans through 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 ...
user159729's user avatar
1 vote
1 answer
45 views

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 ...
user3595231's user avatar
0 votes
2 answers
546 views

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 ...
Ordinary Sail's user avatar
3 votes
2 answers
429 views

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) ...
user993269's user avatar
0 votes
4 answers
322 views

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. ...
Cường Đặng Cao's user avatar
2 votes
1 answer
547 views

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 ...
Vexea's user avatar
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0 votes
1 answer
74 views

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
heloitsme's user avatar
3 votes
1 answer
411 views

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 ...
murphy's user avatar
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-1 votes
1 answer
47 views

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 ...
bwat's user avatar
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0 votes
1 answer
573 views

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 ...
user avatar
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1 answer
124 views

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 ...
Sedat Kapanoglu's user avatar
3 votes
2 answers
171 views

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 ...
pevik's user avatar
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0 votes
1 answer
921 views

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 ...
Kookie Run's user avatar
0 votes
1 answer
323 views

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 ...
kay's user avatar
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