DHCP Relay question

Answered Question
Mar 31st, 2008

Hello experts,

Hope you can help me with this scenario:

PC

|

(NM-16ESW)

c2691#1

(Fast0/0)

|

L2_Sw - PCs

|

(Fast0/0)

c2691#2

I have a DHCP pool configured in router c2691#2, which leases IP addresses to the PCs

attached to L2_Sw. I need to plug a PC on one of the 16 ports available in the NM-16ESW

module of the c2691#1 router and that PC should take an IP address from the DHCP pool

configured in c2691#2 router.

I have done a lot of configuration but I haven't had any luck so far. Is this possible?

Can somebody help me with the correct configuration of both routers?

Here is my last try:

*********

c2691#1

*********

ip dhcp relay information option

ip dhcp relay information trust-all

!

!

interface FastEthernet0/0

ip address 172.31.34.6 255.255.255.0

ip helper-address 172.31.34.2

duplex auto

speed auto

standby ip 172.31.34.1

standby priority 130

!

!

interface FastEthernet1/0

Description PC goes here!!!

duplex full

speed 100

spanning-tree portfast

!

interface FastEthernet1/1

spanning-tree portfast

!

interface FastEthernet1/2

spanning-tree portfast

!

:

interface FastEthernet1/15

spanning-tree portfast

!

interface Vlan1

no ip address

!

*********

c2691#2

*********

ip dhcp relay information trust-all

no ip dhcp use vrf connected

ip dhcp excluded-address 172.31.34.1 172.31.34.89

ip dhcp excluded-address 172.31.34.99

!

ip dhcp pool POOL

network 172.31.34.0 255.255.255.0

default-router 172.31.34.1

dns-server 172.16.3.100 172.16.3.101 172.17.4.11

lease 2

!

interface FastEthernet0/0

description CONEXION LAN

ip address 172.31.34.2 255.255.255.0

duplex auto

speed auto

standby ip 172.31.34.1

standby priority 150

standby preempt

!

Thanks in advanced!!!

Juan Corrales

Network Specialist

ITS/FIFCO CR

I have this problem too.
0 votes
Correct Answer by Karel Vins about 8 years 8 months ago

Could you connect router to switch via switch module? Use fa1/15 instead of fa0/0?

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Overall Rating: 5 (2 ratings)
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Karel Vins Tue, 04/01/2008 - 03:29

Hello Juan,

did you try to configure fa0/0 on c2691#1 as standard switched interface?

Karel Vins

Juan Pablo Corr... Tue, 04/01/2008 - 06:28

Hello Karel,

I cannot do that because I need f0/0 as a layer 3 interface doing HSRP with f0/0 of router 2691#2.

Juan Corrales

Karel Vins Tue, 04/01/2008 - 06:40

Hi Juan,

is it possible to use Vlan 1 interface as L3 interface instead of fa0/0?

Karel

Juan Pablo Corr... Tue, 04/01/2008 - 07:04

What's the configuration you're suggesting? Configure F0/0 as a trunk and use Vlan 1 as the L3/HSRP interface?

Karel Vins Tue, 04/01/2008 - 07:11

My suggestion is:

1) configure fa0/0 as switched access port in Vlan 1 and try if DHCP is working,

2) configure Vlan 1 as L3/HSRP interface.

I thing that fa0/0 can be access port not trunk port if you don't need more than one Vlan between router and switch.

Juan Pablo Corr... Tue, 04/01/2008 - 09:09

How can I configure a pure Layer 3 interface as an access switch port? I don't have any switchport commands available.

Karel Vins Tue, 04/01/2008 - 09:16

Ou, it's my mistake. I didn't realize that fa0/0 is not interface of switch module.

Correct Answer
Karel Vins Tue, 04/01/2008 - 09:29

Could you connect router to switch via switch module? Use fa1/15 instead of fa0/0?

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