Router doesn't send a DHCP OFFER

hdgorod

Hello to the community,

I am prepering for my CCNA exam and have the following task and issue:

I Have the following network devices in gns3: 
- R1: c3725 router and works as DHCP Server
- ESW1: a c3745 Router with NM-16ESW Slot, therefore operates es L3 Switch
- PC1: Is VPCS

Here the network topology:
- R1 f0/0 connected to ESW1 f1/0
- PC1 e0 connected to ESW1 f1/1

I have the following tasks:
1) Exclude first 10 IP addresses in subnet from pool
Pool name = vlan10
2) Network = 10.1.10.0/24 (Vlan 10)
3) Default Gateway = ESW1
4) DNS Server = R1
5) Make sure PC can ping the loopback of R1
6) Configure IP Helper, so PC1 can send DHCP Discover to R1

Here the IP Plan:
R1 f0/0: 10.1.1.254/24
R1 Loopback: 1.1.1.1/32
ESW1 f1/0: 10.1.1.1/24, and belongs to int vlan1
ESW1 f1/1: 10.1.10.1/24, and belongs to int vlan10

I have configured everything as it has to be configured. I can ping the loopback on R1 from the PC1 and back, but when PC1 sends DHCP Discover, R1 does recieve it, but doesn't send a DHCP offer. And i don't understand why. Because in Packet Tracer the same configuration works fine, but in gns3 it doesn't.

Here the output on R1 after i habe enabled debug ip hdcp packet:

*Mar  1 01:59:10.971: UDP: rcvd src=0.0.0.0(68), dst=10.1.1.1(67), length=372

*Mar  1 01:59:10.971: DHCPD: DHCPDISCOVER received from client 0100.5079.6668.00 on interface FastEthernet0/0.

R1#

*Mar  1 01:59:11.975: UDP: rcvd src=0.0.0.0(68), dst=10.1.1.1(67), length=372

*Mar  1 01:59:11.975: DHCPD: DHCPDISCOVER received from client 0100.5079.6668.00 on interface FastEthernet0/0.

R1#

*Mar  1 01:59:14.987: UDP: rcvd src=0.0.0.0(68), dst=10.1.1.1(67), length=372

*Mar  1 01:59:14.987: DHCPD: DHCPDISCOVER received from client 0100.5079.6668.00 on interface FastEthernet0/0.

R1#

*Mar  1 02:19:26.947: UDP: rcvd src=0.0.0.0(68), dst=255.255.255.255(67), length=372

*Mar  1 02:19:26.947: DHCPD: DHCPDISCOVER received from client 0100.5079.6668.00 on interface FastEthernet0/0.

R1#

*Mar  1 02:19:27.951: UDP: rcvd src=0.0.0.0(68), dst=255.255.255.255(67), length=372

*Mar  1 02:19:27.955: DHCPD: DHCPDISCOVER received from client 0100.5079.6668.00 on interface FastEthernet0/0.

R1#

*Mar  1 02:19:30.963: UDP: rcvd src=0.0.0.0(68), dst=255.255.255.255(67), length=372

*Mar  1 02:19:30.963: DHCPD: DHCPDISCOVER received from client 0100.5079.6668.00 on interface FastEthernet0/0.

R1#

Does anyone have an idea, why it doesn't work in gns3? May be there is some issue with the L3 switch? Or something of that kind?

hdgorod

Here is the running config of R1: 

R1#sh run

Building configuration...

...

!

hostname R1

!

...

!

!

no ip dhcp use vrf connected

ip dhcp excluded-address 10.1.10.1 10.1.10.10

ip dhcp excluded-address 10.1.20.1 10.1.20.10

!

ip dhcp pool vlan10

   network 10.1.10.0 255.255.255.0

   default-router 10.1.10.1

   dns-server 10.1.1.254

!

ip dhcp pool vlan20

   network 10.1.20.0 255.255.255.0

   default-router 10.1.20.1

   dns-server 10.1.1.254

!

!

no ip domain lookup

!

...

!

!

!

!

interface Loopback0

 ip address 1.1.1.1 255.255.255.255

!

interface FastEthernet0/0

 ip address 10.1.1.254 255.255.255.0

 duplex auto

 speed auto

!

...

!

ip forward-protocol nd

ip route 10.1.10.0 255.255.255.0 10.1.1.1

ip route 10.1.20.0 255.255.255.0 10.1.1.1

!

!

no ip http server

no ip http secure-server

!

no cdp log mismatch duplex

!

!

!

!

!

!

...

!

!

end




Here is the running config of ESW1: 

ESW1#sh run

Building configuration...

Current configuration : 2759 bytes

!

...

!

hostname ESW1

!

...

!

interface FastEthernet1/0

 duplex full

 speed 100

!

interface FastEthernet1/1

 switchport access vlan 10

 duplex full

 speed 100

!

interface FastEthernet1/2

 switchport access vlan 20

 duplex full

 speed 100

!

interface FastEthernet1/3

 duplex full

 speed 100

!

...

!

interface Vlan1

 ip address 10.1.1.1 255.255.255.0

!

interface Vlan10

 ip address 10.1.10.1 255.255.255.0

 ip helper-address 10.1.1.254

!

interface Vlan20

 ip address 10.1.20.1 255.255.255.0

 ip helper-address 10.1.1.254

!

ip forward-protocol nd

ip route 1.1.1.1 255.255.255.255 10.1.1.254

!

!

...

!

end

hdgorod

Ok, I have found the solution.
There was really a problem with the L3 switch I have used.