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.
411
questions
0
votes
1answer
28 views
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.
...
0
votes
0answers
18 views
Machine cannot pickup DHCP, however with static IP gets internet, yet cannot ping [closed]
I have a rather complex issue for you guys, Below is the network topology for a small business I help with networking and computer setups, etc. The end PC on the chain is actually a CNC machine for ...
0
votes
2answers
46 views
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 ...
2
votes
1answer
26 views
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 ...
1
vote
1answer
50 views
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 ...
0
votes
1answer
43 views
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 ...
0
votes
0answers
12 views
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 ...
3
votes
1answer
2k 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 ...
27
votes
8answers
19k views
Why does DHCP use UDP and not TCP?
DHCP uses UDP as its transport protocol. DHCP messages that a client sends to a server are sent to well-known port 67 (UDP—Bootstrap Protocol and DHCP). DHCP Messages that a server sends to a client ...
2
votes
1answer
6k views
How to configure DHCP Relay Agent with multiple VLANs?
I have a network with 2 routers.
Router 0 is a DHCP server and Router 1 I assume should be a relay agent. The routing protocol I use is EIGRP.
The problem is that PC in vlan 15 and vlan 20 cannot get ...
1
vote
1answer
63 views
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 ...
0
votes
0answers
23 views
Cisco FTD DHCP option codes
I have a Cisco ASA 5515-X that is currently running ASA with the FirePOWER module, which cannot sent option code 60 in the DHCP request. My ISP requires me to send this.
Does anyone have FTD 6.4 (or ...
2
votes
1answer
830 views
meraki bridge mode: dhcp is untagged
We have the following set-up:
+------+ +--------+ +--------+
|Router|-----| switch |-----| Meraki |
+------+ +--------+ +--------+
|
+---------+
...
2
votes
1answer
2k views
Can I use PPPoE and DHCP simultaneously?
In terms of subscriber management, I understand there are two major approaches - DHCP and PPPoE.
I know I'm being very general, so give me some rope.
If using DHCP, RADIUS/AAA will authenticate the ...
2
votes
2answers
521 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 ...
0
votes
0answers
22 views
DHCP helper flow in incorrect config
Discovered a configuration error in our network and would like to double check if the conclusions I drew from it are correct.
Incorrect configuration:
dhcp helper set on VLAN xyz to point at DHCP01 ...
2
votes
1answer
463 views
NXOS DHCP Relay - overwriting Option 54 (Server Identifier) differently in DHCPDISCOVER vs. DHCPREQUEST?
I'm trying to sort a DHCP relay problem in a VLXAN/EVPN environment (Cisco N9K, NXOS 9.3.2).
We seem to be able to get DHCPDISCOVERs through to the server and DHCPOFFERS back from there. DHCPREQUESTs ...
1
vote
2answers
710 views
Switch0 is configured as DHCP server but not working?
Here I am not able to obtain ip automatically using DHCP.
Here is configuration of swtich0 which is having DHCP Server.
Switch#sh run
Building configuration...
Current configuration : 1237 bytes
!
...
4
votes
3answers
946 views
can a cisco ASA be configured as a DHCP server for a VLAN on a subinterface? and route packets between VLANs?
We are in the process of planning to phase out a Sonicwall tz205 in our office. i am hoping to replace it with a CISCO ASA 5516 specifically. We have three networks in house the main production ...
1
vote
1answer
42 views
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 ...
1
vote
0answers
28 views
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 ...
0
votes
1answer
141 views
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)> ...
1
vote
1answer
127 views
How to implement port security in SDN using pox controller and ovs?
How can I defend against DHCP starvation attacks or MAC spoofing in an SDN environment?
0
votes
0answers
14 views
Next-server option missing in dhcp server on EXOS switch
I'm trying to utilize the build-in DHCP server on our EXOS switch.
Address pools work as intended. So far so good. But I also need to boot our FOG iPXE server through it. The configuration of the ...
2
votes
3answers
558 views
DHCP on CISCO 3850
I would like to configure the DHCP server on CISCO 3850, and reserve around 100 static IP for servers
After doing research found that I need to create individual pool for each static maping like ...
1
vote
2answers
152 views
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 ...
4
votes
4answers
21k views
DHCP server for multiple VLANs
Good afternoon, I'm learning how to build a network, and I'm trying to add a DHCP server for all VLANs, but I don´t understand how to make it work for all hosts regardless of whether they are on the ...
2
votes
3answers
5k views
Trying to get DHCP working across three VLANs
I have a packet tracer file with 3 switches and 3 VLANs for a school. It is divided up into VLAN 10, 11 and 12. VLAN 10 is for classrooms 1 and 2, VLAN 11 is for classrooms 3 and 4, and VLAN 12 is for ...
0
votes
1answer
87 views
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 ...
2
votes
2answers
332 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 ...
1
vote
2answers
491 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 ...
4
votes
3answers
153 views
Interface VLAN IP address not on exclude list?
Does an IP address need to be included in a ip dhcp excluded-address x.x.x.x if its already included in an interface vlan?
Examples:
ip dhcp excluded-address 10.3.8.1 10.3.8.20
interface Vlan30
...
1
vote
2answers
247 views
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 ...
3
votes
3answers
3k views
How to enable DHCP Cisco router
This is what I have done in my GNS3
R3 - Router
R4 - Switch
I have installed GNS3 and trying to enable on Router as mentioned above depict.
How to enabled DHCP on Cisco router R3 ?
0
votes
1answer
70 views
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 ...
0
votes
4answers
205 views
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, ...
1
vote
2answers
52 views
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 ...
0
votes
3answers
2k views
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 == ...
0
votes
1answer
40 views
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 ...
1
vote
3answers
317 views
Can you keep DHCP addresses from your ISP
I have my modem configured for bridge mode. I get one IPv4 for my router and one goes to my server for public access. If I static assigned these IPv4 address would I keep them as long as no one else ...
0
votes
0answers
9 views
Cisco RV345P - disable DNS names for DHCP bindings
This is about Cisco RV345P router (non-IOS, it's the Web interface kind).
When the hosts on our office LAN obtain address from DHCP their host name is automatically registered in a local DNS resolver ...
18
votes
4answers
24k views
Cisco APs ignore DHCP Option 43 and use CAPWAP UDP broadcasts
Background
I am trying to redeploy Cisco 1242 LWAPs on new Cat4507R+E switches, which means the IP address of the WLC is changing for that LWAP. For some reason, I have to configure ip helper-...
0
votes
2answers
34 views
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 ...
0
votes
1answer
17 views
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 ...
1
vote
4answers
161 views
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 ...
1
vote
1answer
59 views
Will devices with static addresses, will be disconnected when DCHP 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....
0
votes
2answers
111 views
Correctly Setting up DHCP for Intervlan Routing
I am currently building a network and would like my two switches connected to my router to automatically assign ip addresses through DHCP pools to my PC's and devices. I have 4 separate VLans being ...
4
votes
2answers
1k views
VLANs allowed vs VLANs active — cannot pull DHCP over WiFi
I am trying to set up a new WLAN. Cisco 5508 controller. W2K8R2 for DHCP.
Why would VLAN 600 not appear as active in management domain?
I have an AP (Aironet 1041) assigned to VLAN 600. I am unable ...
0
votes
1answer
188 views
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 ...
12
votes
6answers
37k views
Is a DHCP offer packet a broadcast or unicast?
DHCP OFFER is a layer3 broadcast because the server don't know client Ip, but server knows the client mac address. So how it would be the broadcast?
If anyone ask me about this? how should I answer? ...
