DHCP Relay using Brocade Switches

Hi
I have a large project with 3 UCM cluster with unity cluster and UCCX
The network is a Brocade switch environement,
The Core is using OSPF and distribution is Layer 2.
I have configured the Cluster with a dedicated DHCP and TFTP service.
DHCP relay is not working, but when i configure one of the phones with a static IP address it registers and I have full functionality
When I connect my server dirrectly to the core which is not the design then the dhcp relay works and I get an IP address, but when i traverse the layer2 then i do not get an address.
In the same topology I connected a Windows DHCP server on the same vlan as my UCM cluster and change the relay address to point to the windows dhcp the i do get an address.
In an additional test i configured the same setup on cisco switches then the relay works great.
If anyone has seen or knows of any bug regarding DHCP relay i would be greatful for info
Thanks
Lance

Hi Experts,
i forgot to mention that i was reading an interesting document on Cisco website "network virtualization design guide", and they clearly mentioned the below:
"""VRF-awareness for DHCP-relay functionality is currently not supported on any Catalyst platform, but it is required only for supporting overlapping IP addresses"""
So i would like to ask you if you have any workaround to be done in such deployments
Thank you in advance
Samer Labaky
CCIE # 24675

Similar Messages

RV320: DHCP Option 82 + DHCP relay at Ethernet switch

We purchased a RV320 router and want to use the DHCP Option 82 IP Assignment in combination with a ZyXEL GS1910-24 Smart Managed Switch.
The switch is able to insert Option 82 Circuit-IDs into DHCP requests, if they are relayed to a specific DHCP server. So there must be configured exactly one IP address of the DHCP server in the switch configuration (eg 192.168.1.1). The problem is, that the RV320 creates different IP subnets for different Circuit-IDs. So the RV320-router has multiple IPs, one unique IP per subnet (192.168.1.1, 192.168.2.1, 192.168.3.1, ...).
How can I use the Option 82 IP assignment with this configuration?
Is a routing/firewall rule at the RV320 a solution (to forward DHCP requests from subnet specific IP - eg 192.168.3.1 - to exactly one IP, eg 192.168.1.1)?

mpyhala,
seems not to work as the RV320 is restricted to 6 custom VLANs (+ 1 Management VLAN with ID 1).
Maybe I should describe the whole scenario, which should be implemented:
The configuration is like for a small hotel: each room should be logically seperated from each other (no inter-room traffic for security) and each rooms bandwidth should be managed.
Bandwidth management at the RV320 relies on IP addresses. So I need to achieve somehow, that a room (= port number on switch) is always assigned a specific IP address.
14 rooms should be covered in that way.
The problem is currently the link IP<->Switch Port. I thought DHCP option 82 is the way to go, but VLANs (one VLAN for each room) may be also a solution. Unfortunately none of the two ways work.
What can be a solution? Was the RV320 the wrong decision (not enough flexibility)?
Thanks.

Switches that do dhcp relay (ip helper address)

Hi all,
I'm looking at this switch the 1810 24g and I was wondering whether it dose dhcp relay (ip helper address) ie forward dhcp addresses from the dhcp server to the switch?
Many thanks
Rob

Hi,
on all the vlan interfaces where the DHCP server doesn't reside you must configure
interface Vlan
description Client VLAN
ip helper-address
When a client now sends DHCP request, the router
forwards this request to the ip helper-address.
Because the router also puts in its own interface ip address as source ip, the packet finds the way back.
DHCP uses UDP port 67 and 68. With the command ip helper-address, there are also some other ports which are opened for udp. To close this ports you configure (global command)
no ip forward-protocol udp tftp
no ip forward-protocol udp nameserver
no ip forward-protocol udp domain
no ip forward-protocol udp time
no ip forward-protocol udp netbios-ns
no ip forward-protocol udp netbios-dgm
no ip forward-protocol udp tacacs
On your DHCP Server you have to configure a scope for each ip subnet.
If your dhcp server is located at ther server vlan, do NOT configure a helper-address there.
For the migration I would suggest to use two different ip subnets. Image all your clients are now in VLAN2 10.2.0.0/16. If you have this IP subnet on your Router you can't add a new VLAN with 10.2.1.0/24, because this overlaps.
So make the new VLANs with 10.3.1.0/24, 10.3.2.0/24, ... and move the clients to the new
vlans by change the vlan of the port where the PC is conneted to. When you then reboot the PC it shoud get a new ip from the dhcp and everything sould be fine.
Bye
Jo

Suggestions on DHCP using cascading switches

Is there any reason you can't create a different vlan and create a new scope for that vlan on your current dhcp server along with helper addresses on your switches? It seems you're over complicating things as of right now.

gents,we like to provide a WLAN Network for guests in our Company which is connected through a different Provider than our internal Network.I connected the incoming hardline to one router - providing WLAN #1 with DHCP.I like to route it to two floors, using the LAN environment.I have only ONE line available to get the Provider to our Switch-rack.My idea is to connectthe LAN-port of WLAN-Router #1 to the Switch rack and attach another WLAN-Routers to the other floors.My question is: what is the best way to provideDHCP ?a) Router#1 is doing DHCP and all connected secondary routers are just passing through.b) every Router is doing DHCP for himselfI once read that there could be Problems using cascading Switches/Routers. Any enlightment here?
This topic first appeared in the Spiceworks Community

FCoE using Brocade cards CNA1020 and Cisco Nexus 5548 switches

All,
I have the following configuration and problem that I am not sure how to fix:
I have three Dell R910 servers with 1TB of memory and each has two brocade 1020 CNA cards dual port. I am using distributed switches for the VM network and a second distributed switch for VMotion. I have two of the 10G ports configured in each distributed switch using IP Hash. The management network is configured using a standard switch with two 1G ports.
The Nexus configuration is we have two nexus 5548 switch connected together with a trunk. We have two VPC's configured to each ESX hosts consisting of two 10gig ports in each VPC with one port going to each switch. The VPC is configured for static LAG.
What I am seeing is that after a few hours the virtual machines will not be accessible via network anymore. So if you ping the VM it will not work and if you get on the console of the VM then ping the gateway then nothing as well but if you try to ping another virtual machine on the same host on the same VLAN then it will work so traffic is going through the ESX backplane. If I reboot the ESX host then things will work again for another few hours or so then the problem repeats.
The version of vSphere I am using is ESXi4.1
Please assist I am stuck.
Thanks...

Here is the link for Nexus and Brocade interoperability Matrix
http://www.cisco.com/en/US/docs/switches/datacenter/mds9000/interoperability/matrix/Matrix7.html#wp313498
usually this table would show those models those have been tested and verified
However I do not see Brocade 5300 listed in the table . It could be, interoperability may have not been tested by both vendors perticularly to 5300 type Model.

I need to switch a 12V relay using USB6211.i am stuck with programming

i need to switch a 12V relay using USB6211.i am stuck with programming using daq assistant. i am doing hardware implementation also..can anyone give some help...

You can create tasks with individual lines and ports and then have multiple tasks all running for the same device. I would highly recommend the DAQmx VI API. It gives a little better control and is easier to see exactly what is happening.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

WRVS4400Nv2 DHCP Relay on 2nd VLAN

Hi,
Here's what I'm trying to figure out:
My network is set up such that I have a Wireless Network in VLAN 1, which is the primary network that we use. The subnet is 10.5.1.x.
My goal is to set up a completely isolated Guest Wireless Network, however it would work best. What I am trying to do now is I created a seperate VLAN (VLAN 2, IP range 10.5.2.x) and turned on DHCP on the WRVS4400N. However, in the Guest Network, it is always picking up a 10.5.1.x IP which is handed out by the DHCP server (10.5.1.5, Win 2003) and still routing all of the traffic to/from our private network.
Here's What I have set:
Wireless>Security Settings>Guest Network (SSID 2)
Wireless Isolation (between SSID w/o VLAN): Enabled
Wireless Isolation (within SSID): Enabled
Setup>LAN>VLAN 1
Router IP 10.5.1.1, WLAN IP 10.5.1.3
DHCP Relay for 10.5.1.5
Setup>LAN>VLAN 2
Router IP 10.5.2.1
DHCP Enabled for 10.5.2.x subnet
DHCP Relay option is grayed out (not sure why)
Setup>Advanced Routing
Inter-VLAN Routing: Disabled
Any way to solve this would be fine. I just do not want traffic routing through our internal network. Ideally, if I could get the Windows server to hand out 10.5.2.x addresses, that would be perfect, but I'm not sure how to configure it for such.
If anyone has any ideas, that'd be great- thanks!
Matt

Yes...here's an answer I got from Cisco's Engineering support:
The issue you reported is a know issue.
Engineering and development are aware of this issue, and have provided the following information:
PROBLEM DESCRIPTION:
If the WRVS4400N is configured with multiple VLANs, and these VLANs are mapped to different SSID, the user cannot use an external DHCP server to provide IP scopes for these VLANs.
Hosts connected to both SSID will obtain IP address from native DHCP server only.
The workaround for this is to use the embedded DHCP server for all VLANs defined on the WRVS4400N.
Note: This is not considered a bug but rather a product limitation. The developer has confirmed the WRVS4400N is functioning as designed.
Regarding a fix:
Due to wireless and trunk switch port using different chip set, it is not possible to provide a fix for this issue.
In future product, Engineering & Dev teams will strive to use the same chip set (same vendor).
This functionality has been targeted for next new Product. No fix will be made on the current hardware.
Note: If this feature/function is mission critical to your deployment, and you would like to recover the cost of the WRVS4400N, please forward the serial number and a copy of the proof of purchase, and we will gladly provide a refund.
Best regards,
Alex Delano

PXE with IP Helpers/DHCP Relay

I'm a Sysadmin and I have a question about what is best practice in regards to PXE servers. We are currently using DHCP Options for PXE clients (options 66,67). This works for most clients but is not the recommended method from either of the vendors we have used (Microsoft or Symantec). They recommend using IP Helpers / DHCP relay to forward the DHCP discover request to the PXE servers so that the PXE server is getting the actual request. This is more of an issue now with UEFI-based machines where the boot file would be different based on if the client is UEFI.
My Network team is against using IP Helpers and thinks it can cause issues. This doesn't seem to make much sense to me, as from what I understand, all that happens is both the DHCP server and the PXE servers get the DHCP discover and respond with their relevant info. Can someone clarify what, if any, issues there are using multiple IP helpers/DHCP relay with PXE Servers like SCCM & Altiris? Is this not standard practice?

It's very common to use DHCP relays (IP helpers) in order to centralize DHCP infrastructure. Larger organizations will frequently use this approach in order to avoid having to manually edit DHCP configurations at the router or switch level. Having a few servers with a central DHCP configuration for all segments is a good management proposition.
In most environments, there isn't a problem with doing this, but it is a major architectural consideration and not something you just turn on without consideration. This is largely because DHCP works on a broadcast principle. The clients are going to broadcast for the first DHCP server that answers with an acceptable offer, which they will take. If you have a mixture of local DHCP servers and relays, the local servers will respond faster and may not provide the configuration you want to deploy... at best. At worst, you will have a mix of acceptable responses and a lot of potential for conflicting addresses. On any network segment where you're using DHCP relays, the local server needs to be disabled.
It might be worthwhile going back to your network team and asking what sorts of "issues" that they feel the implementation of DHCP relays would cause. There may be something unique to your environment that makes them reluctant to pursue this approach.

VWLC DHCP relay flooding

Hello.
I have a big problem with a vWLC installation and the DHCP relay. I have a interface for guest access in central Switching mode where is a DHCP Server address which is not in the same subnet. The Proxy mode is on, and the vWLC can reach the DHCP over its default gateway on the Interface. When a clients connects to ssid it sends a DHCP request and the controller sends it with its interface ip to the DHCP. So far so good, but the problem is that the vWLC does not send one packet, it sends thousends of same DHCP requests to the Server. The DHCP Server also ansers with thousends of DHCP acks.
When i give the DHCP which is also a vm, a interface in the guest vlan everthing works correct. Does anybody know if there is a problem with DHCP relay over Layer 3?
Regards Stefan
I use the latest verion of vWLC.

Hello.
I have a big problem with a vWLC installation and the DHCP relay. I have a interface for guest access in central Switching mode where is a DHCP Server address which is not in the same subnet. The Proxy mode is on, and the vWLC can reach the DHCP over its default gateway on the Interface. When a clients connects to ssid it sends a DHCP request and the controller sends it with its interface ip to the DHCP. So far so good, but the problem is that the vWLC does not send one packet, it sends thousends of same DHCP requests to the Server. The DHCP Server also ansers with thousends of DHCP acks.
When i give the DHCP which is also a vm, a interface in the guest vlan everthing works correct. Does anybody know if there is a problem with DHCP relay over Layer 3?
Regards Stefan
I use the latest verion of vWLC.

How to configure Dhcp relay agent

How I can to configure the wrt54g like a dhcp relay agent? please i need help, tell me

A DHCP relay agent is any host that forwards DHCP packets between clients and servers. Relay agents are used to forward requests and replies between clients and servers when they are not on the same physical subnet. Relay agent forwarding is distinct from the normal forwarding of an IP router, where IP datagrams are switched between networks somewhat transparently. By contrast, relay agents receive DHCP messages and then generate a new DHCP message to send out on another interface. The relay agent sets the gateway address (giaddr field of the DHCP packet) and, if configured, adds the relay agent information option in the packet and forwards it to the DHCP server. The reply from the server is forwarded back to the client after removing option .

Can I use ASA to be a DHCP Server use in WLC wireless Client

I want to use ASA to be a DHCP Server for Wireless Client not it can't.
I check the debug log in WLC, I confirm the WLC have send the request to ASA.
In the ASA, it don't have any hits in the rule when the WLC send the DHCP relay request.
I have try don't use dhcp relay in WLC but don't success. Anybody have the same case with me? And Is the ASA can't support DHCP relay agent to request to get the IP Addr.
P.S. In the Network Design limitation so I can't use WLC to be DHCP Server.
Equipment:
ASA5510
WLC4402
How can I fix it.
Thank you very much

The issue is that the ASA doesn't accept DHCP requests from a relay agent, only broadcast DHCP requests. In the 4.2 version for the controllers there is now an option so you can change the way the controller forwards DHCP requests so that it is sent as a broadcast and not from a relay agent.

How to tell N6.5 DHCP to use a W2k8 for PXE?

Hello,
could anyone give me a hint, how to tell my netware DHCP to use a Windows Server 2008 R2 running Acronis with PXE Server?
Actual Situation:
Netware 6.5 Sp8 Server with ZENWORKS in Cluster mode
Netware DHCP Server
ZEN7 SP1 Imaging
--> works fine so far, and no problem in other subnets, IP-helper are configured in the switches
New Situation:
Netware 6.5 Sp8 Server with ZENWORKS in Cluster mode
Netware DHCP Server
Windows Server 2008 R2 running Acronis Snap Deploy with PXE-Server - in future may be a clean Windows Deployment service without Acronis
--> that would be nice :)
I found serveral ini-files (dts.ini, pdhcp.ini, tftp.ini) where I configured the new IP-Address of the W2k8 PXE Server.
Now:
The Client gets its correct IP-Address from Netware DHCP
but after that the following messages:
Auto-select:
ZENworks Boot
Boot Server IP: --.--.--.-- (the correct one configured in the ini-files!)
TFTP.
PXE-T02:
PXE-E3C: TFTP Error - Access Violation
PXE-M0F: Exiting Intel Boot Agent
Any ideas?
Thanks a lot.

Originally Posted by magic31
You don't have to configure anything specifically in DHCP to work with PXE. Possibly just unconfigure an option that was set for the previos setup; One thing to check (and remove) is option 60 for the PXE Client option, if this is configured with the DHCP subnet options. This option should only be set if both DHCP and PXE services are on the same server (as is probably the case in your situation as I'm guessing both DHCP as also PXE get loaded in the same cluster resource script).
For subnets serviced outside of the subnet your DHCP server is running in, you will need to configure multiple ip helpers: one that points to the DHCP server and one points to the PXE server so those requests on other subnets get serviced correctly.
To get things running it's probably easier to try to get this to work on the subnet your DHCP and PXE server are running in (so you are not also having to deal with the ip helper setup just yet). If that works, then expand you configuration to different subnets & ip helpers.
Hope that helps,
Willem
As a ps and for clarification, don't load the PDHCP on any of the NetWare servers... just have the PXE PDHCP service running on the Windows server.
The PDHCP/PXE service for ZenWorks won't understand/work with the Arconis one and visa versa.
-Willem

Setting up a DHCP relay agent

Hello,
I'm trying to setup a relay agent for an XP client to obtain configuration through 2 routers on a VM LAB
I have 3 Segments/subnets 1,2 and 3
the topology is the following:
1- server 2008 R2 AD DS DC on subnet 1 (192.168.1.0) and a DHCP server with 2 scopes
Internal 192.168.1.0 (subnet1)
external 192.168.3.0 (subnet 3)
2- server 2008 R2 with RRAS installed
Interface 1 pointing to the internal subnet1 192.168.1.0
Interface 2 pointing to subnet2 192.168.2.0
3- server 2003 with RRAS installed
Interface 1 pointing to subnet2 192.168.2.0
Interface 2 pointing to subnet3 192.168.3.0
relay agent installed on Interface 2
(servers/Routers 2 and 3 running RIP v2)
4- XP client on subnet3 (192.168.3.0) and the client trying to obtain config.
The XP client is unable to contact the DHCP to obtain config.
server 2003 relay agent receiving requests with no replies.
How do i get this to work?

Hi,
First, let’s see how DHCP relay agent works:
1. The DHCP client broadcasts a DHCPDISCOVER packet.
2. The DHCP relay agent on the client’s subnet forwards the DHCPDISCOVER message to the DHCP server by using unicast.
3. The DHCP server uses unicast to send a DHCPOFFER message to the DHCP relay agent.
4. The DHCP relay agent broadcasts the DHCPOFFER packet to the DHCP client’s subnet.
5. The DHCP client broadcasts a DHCPREQUEST packet.
6. The DHCP relay agent on the client’s subnet forwards the DHCPREQUEST message to the DHCP server by using unicast.
7. The DHCP server uses unicast to send a DHCPACK message to the DHCP relay agent.
8. The DHCP relay agent broadcasts the DHCPACK to the DHCP client’s subnet.
We can see in the second step, DHCP relay agent send unicast to DHCP server after receiving DHCP request. So confirm unicast communication between DHCP server
and DHCP relay agent works fine. At least ping should be working. You can use the following commend to add the route entry.
Add a static IP route
http://technet.microsoft.com/en-us/library/cc757323(v=ws.10).aspx
The result should be based on your test. If it doesn’t work it just indicates that we cannot configure another DHCP relay agent behind a relay agent.
Hope this helps.

ASA 5512-X - VPN & local clients DHCP relaying (DHCP Proxy vs. DHCP Relay conflict)

Hey all,
I have ASA-5512-X serving as general firewall/router. It also serves as AnyConnect SSL VPN gateway (webvpn).
It has ~10 VLANs connected over 1 trunk port. One of the VLANs has DHCP server that shall serve all the VLANs (192.168.16.2).
I'm trying to have the ASA relay DHCP requests from all VLANs to the DHCP server and to also serve VPN clients.
However, according to bug https://tools.cisco.com/bugsearch/bug/CSCsd22469 both DHCP Proxy (webvpn) and DHCP Relay (local interfaces) can't be enabled at the same time.
As VPN clients connect to the same VLANs as local users (eg. VLAN 2 - 192.168.2.0/24) I want to have the very same DHCP server serving both, otherwise it's gonna become a mess.
Note: if I configure DHCP Relay functionality and disable DHCP Proxy - local clients are served fine. If I configure DHCP Proxy (webvpn) and disable DHCP Relay VPN clients are served fine. I therefore consider setup to be correct, just the ASA limitation won't allow me to make it serve both.
Can DHCP Relay also serve VPN clients (no DHCP Proxy enabled)? did I miss something?
Thanks!

Hi,
The only workaround for this issue is to configure the ASA itself to act as DHCP server for vpn clients. You also have the flexibility of using local pool and AAA server. Why exactly do you want to use the same DHCP server for both?
AM

DHCP Relay Cisco SG500X

Hi,
I've create 2 vlan in a cisco SG500X-24 and a DHCP server on vlan 2. I just want to dhcp server assign ip to devices on vlan 3. I've configured the vlan and dhcp server relay commands.
ip dhcp relay address 192.168.1.11
ip dhcp relay enable
ip dhcp information option
interface vlan 2
ip address 192.168.1.250 255.255.255.0
interface vlan 3
ip address 192.168.51.254 255.255.255.0
ip dhcp relay enable
The dhcp server gets the request from pc, and sends a new address, but the offer packet not comes to device. With Wireshark a see like offer dhcp packet can't jump to vlan 3.
It's the first time a work with SMB series, and this never happens with catalyst. I'm turning crazy.
Anyone can help me? Thank you in advances.
Victor.

Hi,
Yes, also I configured ip dhcp relay on intefaces.
Yesterday I found the trouble. I was using the tftpd32 dhcp server, and I tested with a Windows DHCP server and everything works like a champ. I didn't know what have do, and i turned crazy, so I began to change every element on solution, finally the DHCP server that it was the key.
Thank you so much for your answer.
KR!

DHCP Relay using Brocade Switches

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