dhcp relay for vrf

20vek · ‎02-14-2012

Hi,

I am trying to configure two 3845 routers to act as dhcp server and dhcp relay. Clients are connected to the router that relays all dhcp requests to the vrf instance which is used to connect it to the router wich is running dhcp server.

Router1

ip vrf dhcp_dns

rd 8:1

int gi0/0

ip vrf forwarding dhcp_dns

ip address 192.168.200.5 255.255.255.248

int gi0/1.5

encapsulation dot1Q 5

ip dhcp relay information trusted

ip vrf forwarding Client_A

ip address 192.168.201.1 255.255.255.0

ip helper-address vrf dhcp_dns 192.168.200.6

ip route vrf dhcp_dns 0.0.0.0 0.0.0.0 192.168.200.6

Router2

dhcp pool Client_A

network 192.168.201.0 255.255.255.0

default-gateway 192.168.201.1

interface GigabitEthernet0/0

ip address 192.168.200.6 255.255.255.248 interface GigabitEthernet0/0
ip address 192.168.200.6 255.255.255.248

ip route 0.0.0.0 0.0.0.0 192.168.200.5

So far I can see dhcp requests comming from the R1 and dhcp server on R2 replies with the dhcp offer but PC is not getting any ip.

Thank you,

ebarticel · ‎02-14-2012

Maybe the typo on first lines.

ip vrf dhc_dns

rd 8:1

int gi0/0

ip vrf forwarding dhcp_dns

Hope this helps

Eugen

20vek · ‎02-15-2012

Thank you for the reply,

It's a typo in the message... I didn't copy and paste the router config but vrf definition is correct in the router config.

rsimoni · ‎02-15-2012

Hi,

what do you see if you enable dhcp debugs on Router 1?

Riccardo

20vek · ‎02-15-2012

Hi,

This is what I have on the routers. 7206VXR is the dhcp server and 3845 is

the dhcp relay.

It looks like 3845 is forwarding bootrequests and 7206 is replying but PC

still doesn't get ip address...

Regards,

Val Kotliarov ? Certified IT Specialist

IBM Canada Ltd,

IBM Business Continuity and Resiliency Services

3500 Steeles Avenue East, Markham, Ontario, L3R-2Z1

External Number: (905) 316-7312 Tie Line: 886-7312

Cell Number: 416-819-2151

Fax Number: 905-305-9850

Pager Number: 416-2324938

E-MAIL: KOTLIAR@CA.IBM.COM

From: rsimoni

To: Valeri Kotliarov/Markham/IBM@IBMCA

Date: 15/02/2012 10:02 AM

Subject: - Re: dhcp relay for vrf

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Re: dhcp relay for vrf

created by Riccardo Simoni in LAN, Switching and Routing - View the full

discussion

Hi,

what do you see if you enable dhcp debugs on Router 1?

Riccardo

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rsimoni · ‎02-15-2012

can you paste the debug outputs?

would like to make sure the dhcp packet is sent out to the correct interface

20vek · ‎02-15-2012

Done,

I included screen shots for dhcp server and dhcp relay as well.

Regards,

Val Kotliarov ? Certified IT Specialist

IBM Canada Ltd,

IBM Business Continuity and Resiliency Services

3500 Steeles Avenue East, Markham, Ontario, L3R-2Z1

External Number: (905) 316-7312 Tie Line: 886-7312

Cell Number: 416-819-2151

Fax Number: 905-305-9850

Pager Number: 416-2324938

E-MAIL: KOTLIAR@CA.IBM.COM

From: rsimoni

To: Valeri Kotliarov/Markham/IBM@IBMCA

Date: 15/02/2012 10:28 AM

Subject: - Re: dhcp relay for vrf

Home

Re: dhcp relay for vrf

created by Riccardo Simoni in LAN, Switching and Routing - View the full

discussion

can you paste the debug outputs?

would like to make sure the dhcp packet is sent out to the correct

interface

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Start a new discussion in LAN, Switching and Routing at Home

20vek · ‎02-15-2012

Hi Riccardo,

Here it is.

Hi,

This is what I have on the routers. 7206VXR is the dhcp server and 3845 is the dhcp relay.

It looks like 3845 is forwarding bootrequests and 7206 is replying but PC still doesn't get ip address...

rsimoni · ‎02-15-2012

the debug of the 3845 does not show whether it sends the dhcp offer back to the PC. But since it is not the DHCP server it could be simply due to the type of debugs which you enabled.

Try to have a look to the following guide which contains 'enanched' ways to troubleshoot similar issue. Specifically pay attention to the section called "Verify Router is Receiving DHCP Request and Forwarding Requests to DHCP Server Using debug Commands" which includes smart ways to configure debugs ACLs.

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a00800f0804.shtml

The goal is to verify if the issue is on

1. 3845 not receiving dhcp offer from 7206

2. 3845 not forwarding it to the PC (or forwarding it to the wrong interface)

3. PC not receiving it for some reason