Network noob here.

I'm trying to get my DHCP server to issue leases across 2 switches using VLAN 1.

With GNS3, I have 1 VirtualBox guest running isc-dhcp and 2 Cisco switches running IOS 12.4 in a configuration like so:

[dhcp_server]-(eth1) <--> (fa1/0)[switch_1](fa1/1) <--> (fa1/0)[switch_2]  

VLAN 1 is the only VLAN I've configured on both switches:

switch_1# conf t
switch_1# int vlan 1
switch_1# ip address dhcp
switch_1# no shut

and the same on switch_2:

switch_2# conf t
switch_2# int vlan 1
switch_2# ip address dhcp
switch_2# no shut

This successfully configures switch_1 with an ip address from the DHCP server, but switch_2 is unable to get an ip address.

I've tried connecting another guest VM to switch_1, and it's also unable to get an ip address from the DHCP server.

  • 1
    Is all the ports in vlan1 ? If you put a static ip on sw2 can you ping the dhcp server ?
    – Pieter
    Jul 14 '15 at 7:20
  • If it is a continuous layer 2 broadcast domain from the DHCP server to the Vlan 1 inteface on switch2 there should be no problem (no paper!).
    – jwbensley
    Jul 14 '15 at 11:11
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 12 '17 at 3:36

This problem was apparent with GNS3 v0.8.4 from the Ubuntu apt repositories.

The solution was upgrading to v1.3.7 on Windows x64 with VirtualBox v5.0.0. Now everything works as expected.

I'm using the same EtherSwitch IOS image (NM-16ESW).

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