1

I am building a lab environment for CCNA training, using GNS3. The GNS3 network is connected to a real network, let's call it LAN 1.

LAN 1 is not connected to the internet and is completely wired Ethernet. A single instance of GNS3 runs on a Windows 7 Enterprise host. The same host also runs a VMWare Ubuntu 10.0.04 guest. R1 is connected to the Microsoft Loopback adapter (C1), and R2 is connected to the normal Ethernet adapter (C3) as shown in the topology below. ipconfig shows that the Windows 7 host (running GNS3) has IP 10.10.10.167. An nmap scan from this same host, with target set to its default gateway of 10.10.10.252 says that we have a Cisco router (but I don't have physical access to know what model it is).

enter image description here

ipconfig output. 

Ethernet adapter MS-loopback-adapter:

   Connection-specific DNS Suffix  . : 
   Link-local IPv6 Address . . . . . : fe80::78cf:e504:8742:e683%19
   Autoconfiguration IPv4 Address. . : 169.254.230.131
   Subnet Mask . . . . . . . . . . . : 255.255.0.0
   Default Gateway . . . . . . . . . : 

Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . : 
   Link-local IPv6 Address . . . . . : fe80::f0b4:a6be:31b:924%12
   IPv4 Address. . . . . . . . . . . : 10.10.10.167
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 10.10.10.252

Ethernet adapter VMware Network Adapter VMnet1:

   Connection-specific DNS Suffix  . : 
   Link-local IPv6 Address . . . . . : fe80::2997:a8ce:7df5:b968%16
   IPv4 Address. . . . . . . . . . . : 192.168.129.1
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 

Ethernet adapter VMware Network Adapter VMnet8:

   Connection-specific DNS Suffix  . : 
   Link-local IPv6 Address . . . . . : fe80::68ea:2034:c05f:b3f2%17
   IPv4 Address. . . . . . . . . . . : 192.168.14.1
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . :

configuration:

!
ip forward-protocol nd
!
!
no ip http server
no ip http secure-server
!

R1.cfg

!
interface FastEthernet0/0
 ip address 10.10.10.170 255.255.255.0
 speed 100
 full-duplex
!

R2.cfg

!
interface FastEthernet0/0
 ip address 10.10.10.160 255.255.255.0
 speed 100
 full-duplex
!

The problem is that neither R1 nor R2 can ping the Windows 7 host (running GNS3) 10.10.10.167 as shown for R2 below (the console of R1 and R2 are basically the same).

R2(config)#ip address 10.10.10.160 255.255.255.0
R2(config)#no shutdown
R2(config)#ip route 0.0.0.0 0.0.0.0 10.10.10.252

R2#show ip route

Gateway of last resort is 10.10.10.252 to network 0.0.0.0

     10.0.0.0/24 is subnetted, 1 subnets
C       10.10.10.0 is directly connected, FastEthernet0/0
S*   0.0.0.0/0 [1/0] via 10.10.10.252
R2#ping  169.254.230.131

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 169.254.230.131, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
R2#ping 10.10.10.167

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.167, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

I've set the Gateway of last resort to 10.10.10.252 which is the actual default gateway for the real LAN which my GNS3 host is on. Still for both R1 and R2, the ping on 10.10.10.167 (the regular ethernet adapter of the GNS3 host) and the loopback adapter 169.254.230.131 has no success. Why can't R1 and R2 see my real LAN? What am I missing here?

I actually have run into lots questions so far and (assuming this is not off-topic) plan to create a series of posts after this.

T. Webster
  • 346
  • 2
  • 9
  • 20
  • Is your host firewall disabled? That is always the first item to check in regards to host <-> Dynamips hypervisor network connectivity. – mweisel Mar 29 '13 at 22:50
  • @mweisel it is not disabled. There are 4 entries in windows firewall for dynamips and none of them are blocked; all are allow – T. Webster Mar 30 '13 at 00:31
  • @mweisel I upvoted your answer because it the host I was connected to before has firewall disabled. Now I'm using a new host where I decided to enable the dynamics private profile in Windows firewall, and the ping works, however that's not the only thing which has changed, so I don't know if that is really the solution. The actual answer you gave to use a switch doesn't matter in my network as I commented. – T. Webster Mar 30 '13 at 01:42

2 Answers2

1

Also, your topology has the router directly connected to the cloud. You will want to use an Ethernet switch device between the router and the cloud.

GNS3 Topology

mweisel
  • 526
  • 3
  • 4
  • why is a switch necessary? http://forum.gns3.net/topic5663.html http://www.gns3.net/wp-content/uploads/2011/11/gns3-hosts-topology-03.png http://serverfault.com/questions/384628/gns3-connection-to-real-network – T. Webster Mar 30 '13 at 01:42
  • You're correct a direct router to loopback interface (cloud) may work, but it has been in my experience a switch between the two will give you better "luck". This is especially true for the other platforms (OS X and Linux). – mweisel Mar 30 '13 at 02:13
  • Did you reboot after creating the loopback interfaces? This happens to be another "gotcha" that is rarely documented but can be essential to a successful implementation. – mweisel Mar 30 '13 at 02:23
  • One gotcha I noticed about loopback interfaces, http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1007250 – T. Webster Apr 02 '13 at 05:59
1

Can I ask you why you connect your Ubuntu to MS loopback? And the second thing, why is R1 that is connected to MS loopback network having IP address from your LAN IP range (10.10.10.170/24)? This will not work for sure...

Anyway, the working setup here would be:

  1. Ubuntu on VMware should use Bridged network (as we would like to use the same network as our GNS router does). Of course, configure Ubuntu workstation to have address range from your LAN segment. Let us presume LAN segment is: 10.10.10.0/24 from now on...

  2. Disable firewall on Windows 7 machine if FW is on - this is what is blocking the communication when it comes to R2 to Win7 communication.

Other options... If you really want to simulate the scenario where Ubuntu VM and R1 router are connected to one subnet (let us call it Subnet1), and R2 is connected to your regular (LAN) subnet, then follow next scenario:

  1. Setup Network adapter in VMware for Ubuntu machine to be NAT.
  2. Change R1 GNS configuration and bound your GNS3 cloud to VM nat interface.
  3. Configure R1 to match the IP subnet of VMware NAT IP range on your PC.

Cheers, Ana

Ana Peric
  • 56
  • 1
  • because the GNS3 page says so: http://www.gns3.net/gns3-connecting-real-networks/ but I found out that not only is the MS loopback adapter unnecessary to the GNS3 setup with real LAN, but it doesn't work anyway. – T. Webster Apr 02 '13 at 06:01