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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.

2
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1answer
19 views

pfsense DHCP lease remember time settings?

pfSense remembers DHCP leases for a quite long time, which is good use on a LAN where the same machines request IP numbers frequently and have a chance to always get the same leases. However on an ...
0
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0answers
9 views

Multiple DHCP servers detected by access points [closed]

I’m having an issue with our internal network and voip network. I currently have it setup as a non-converged network separating our two data switches and one voip switch. We preferred not having our ...
0
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2answers
39 views

How to give one pc with dhcp a default-gateway while the rest use static ip and static default-gateway

I have this topology where the PC0, Server0 and PC4 use static ip and static default-gateway, but one pc is Request DHCP, so i have to use DHCP ip address for him and static ip for the rest, now the ...
0
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1answer
19 views

How should DHCP servers respond to subsequent requests from same MAC address? [closed]

I'm handling a wireless router device (Asus RT-AC66U) that advertises a so-called Repeater Mode. This mode allegedly picks up an existing WiFi signal and repeats it, while it disables DHCP and NAT ...
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0answers
14 views

is there a way to force a PC to only accept a certain router as its DHCP server? [closed]

i would think you could somehow force the PC to only accept a specific MAC address as a DHCP server. But then is there a way to require the PC verify the DHCP server is actually the DHCP server it's ...
2
votes
1answer
64 views

How to prevent manual assignment of an IP of VLAN/subnet A when connected to a VLAN/subnet B?

I'm configuring a Cisco router C1111-8p using IOS XE 16.8 with 3 VLANs. VLAN 1: native/management 192.168.0.0/24 VLAN 10 : 192.168.10.0/24 VLAN 20 : 192.168.20.0/24 I haven't set ACLs up yet but ...
2
votes
1answer
18 views

Shoretel ST1D Switch not accepting assigned IP

After configuring a Shortel ST1D switch, I connected the LAN1 Port from Shoretel ST1D to my Cisco 4507R switch. I attempted to ping the IP that I set specifically on the ST1D switch and I wasn't able ...
3
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2answers
122 views

How does a DHCP relay router forward the packet to the server?

We know that routers do not forward broadcast messages. So when a DHCP relay router receives a DHCP Discover message, the destination IP address is going to be 255.255.255.255 because at this stage ...
1
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2answers
173 views

Cisco DHCP Router

I have come across an issue and I’m not sure on how to resolve. I’m trying to get the router to assign the PC’s within my network IP addresses. I have excluded the ones which i wish to not be used ...
1
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1answer
24 views

How do devices with static IP behave themselves when plugged to a new network? [closed]

I'm trying to understand how to determine if a device plugged to my PC with Ethernet cable has a static IP. What I'm trying to do is to sniff DHCP packets that it sends and by looking at DHCPDISCOVER ...
1
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2answers
44 views

What happens when DHCP client and server are on different VLANs [closed]

I'm trying to create a lab on PT and I've attached an image. But for some reason my PC is not able to get an IP address from the DHCP server. There is no issues with layer 1 and layer 2. I checked ...
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0answers
41 views

Customized captive portal with external DHCP server [closed]

I am stuck in one issue for which I need your help on this. Actually its bit complex to explan about my situatuion but I will try my best. I am working on customized captive portal on arm processor ...
2
votes
2answers
55 views

Client timeout for Cisco IOS Static DHCP Pool

I'm not a network admin, but I have an old Cisco Catalyst 3560 for my network. I've successfully set up a DHCP Pool: ip dhcp pool 192.168.0.0 network 192.168.0.0 255.255.255.0 default-router 192....
0
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1answer
40 views

Configuring HP Smart Switch and SonicWall with VLAN

I'm trying to configure an HP SmartSwitch with a Dell SonicWall on a VLAN for some computers in our network. The computers in question are on port 37 on the switch. I've created a new VLAN interface ...
0
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0answers
13 views

DHCP Layer 2 and Layer 3 [duplicate]

I am having a difficult time to visualize the conceptions of DHCP Discover message in order to receive an IP address sends out a broadcast at both layer 2 and layer 3. Can someone care to explain? ...
1
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1answer
93 views

No DHCPOFFER message captured in Wireshark

I am looking for the answer why packet captures in Wireshark doesn't contain DHCP offer message. I was trying to capture packets directly on the computer with installed Wireshark and doing a SPAN ...
1
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0answers
26 views

Cisco ASA: Windows DHCP doesn't bind IP address after failover change active [closed]

Equipment and soft: Two Cisco ASA 5540, ASA ver. 9.1(7)32, active/standby failover DHCP server: Windows server 2016 Anyconnect VPN clients get IP addresses from DHCP servers. Everything works ...
1
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0answers
34 views

DHCP over Frame Relay [closed]

I have two co-operate buildings. Building A is connected to building B via frame relay. Building A has the main switch server (with VLAN info) and a DHCP server. I need Building B devices to receive ...
0
votes
1answer
52 views

Is there such a thing as a “fallback” DHCP server? [closed]

Suppose I have a network 10.0.0.0/24, and a DHCP server that allocates addresses under that network. My question is simple — I have a separate box which is also capable of acting as a DHCP server. ...
3
votes
1answer
61 views

Host IP address vs gateway IP address vs DHCP IP address

What is the difference between a host IP address, a gateway IP address, and a DHCP IP address when setting up networking devices? For example, when configuring a virtual network adapter for my VM, I ...
0
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0answers
26 views

Cisco ASA L2TP remote-access VPN with addresses assigned by DHCP

I have an ASA with a working Cisco VPN Client configuration set up. I am trying to phase out the Cisco VPN Client, initially in favour of L2TP. The Cisco Client policy has end-users fetch their ...
1
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1answer
34 views

Cisco 887VA not handing out IPs to new requests

A few days ago seemingly with no changes (other than we changed the adsl mode on the controller). DHCP has stopped working for 2 of the 3 vlans we have configured on a Cisco 887VA. From the Cisco ...
3
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1answer
43 views

ip dhcp class command

Here is a DHCP configuration that we have here: ip dhcp class range ip dhcp pool abc network 10.10.10.0 255.255.255.0 default-router ... class range address range 10.10.10.10 10.10.10.254 My ...
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2answers
64 views

Get DHCP IP with subinterface

Router0 has 1 subinterface on gi0/0 and can't get a ip trough dhcp. Is there something I forgot? The configs: Router0(got no ip from dhcp): interface GigabitEthernet0/0 ip address dhcp duplex ...
1
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1answer
41 views

Dhcp Broadcast Through Switches

Think of a pc connected to switch1. Sw1 is connected to sw2(trunk port on both switches) and sw2 is connected to a router(dhcp server). Pc sends a dhcp broadcast. Does sw1 passes the broadcast through ...
1
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1answer
39 views

DHCP Broadcast on SVI

Think of a dhcp broadcast going through multiple switches. What happens to that broadcast when it reaches the vlan interface (svi)?
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2answers
55 views

How can TCP be used in order to implement DHCP and under which circumstances is this preferable?

I am pretty new to the computer networking studies and was learning about the DHCP protocol. It is implemented based on UDP, as I've gathered, but is there a way for it to be implemented over TCP? ...
0
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1answer
41 views

Why aren't we using digital signatures for the DHCP?

Why aren't we using digital signatures for the DHCP in order to stop Rouge DHCP attacks?
0
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1answer
24 views

faild hardware address for ifd ge-0/0/0 failed on junos-vsrx-12.1X47-D20.7-domestic vmware machine

I have been trying to configure dhcp client on ge-0/0/0, I have asked a question before about it in this link At first the solution provided worked, but when I started the virtual machine again it ...
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0answers
18 views

DHCP Broadcast messages [duplicate]

Why are there so many DHCP broadcast messages while trying to give a computer some network settings? 2.Last,when can these broadcasts be avoided and how are DHCP relay agents related to the whole ...
0
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2answers
150 views

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), ...
3
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1answer
126 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 ...
0
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1answer
34 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 ...
1
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1answer
46 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 ...
1
vote
1answer
59 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 ...
2
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3answers
78 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 ...
0
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2answers
51 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 ...
2
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0answers
48 views

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 ...
3
votes
3answers
515 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 ...
3
votes
1answer
190 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 ...
1
vote
1answer
103 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 ...
1
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0answers
105 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 ...
1
vote
1answer
164 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 ...
1
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1answer
1k 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?...
2
votes
1answer
1k 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 ...
0
votes
2answers
45 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 ...
1
vote
2answers
55 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 ...
2
votes
1answer
91 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 ...
1
vote
1answer
126 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 ...
2
votes
1answer
308 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 ...