There is an unbelievable amount of junk on the net that can send one in all the wrong directions. When it comes to dynamips it is no different and it seems everyone has a different opinion on what works and what does not. It probably depends on the OS dynamips runs on and the alignment of the moon and the stars. For me the best solution thus far was to run Dynamips on Ubuntu Linux server edition. The reasons for this is due to the 100Mb memory Ubuntu server consumes to run the OS as well as the stability and responsiveness of Dynamips on linux. It has worked well.
To break out to real switches I started with the multiple USB adapter approach. Basically you map each USB to Ethernet adapter to a router ethernet port in the dynagen net file. Sounds simple, and while it is, the USB approach for me turned out to be unreliable. It would work, then it would not. This plus the hassle with using USB adapters from different vendors and drivers just becomes messy.
After more research I tried the “switch in the middle” method. This is by far the easiest, quickest, cleanest and most reliable route:
Overview:
So you are probably already using dynamips to run the routers. To break out the first thing is to create a trunk between your linux server and a breakout switch. Then create a bunch of vlans on the linux server. One for every port that will connect to real switches e.g. if R2 needs to connect to the real switches with Fa0/0 and Fa0/1, create two vlans for this router. In the dynagen net file map each ethernet port to the vlan ’sub interfaces’ which were created when the vlans were created. Create the same vlans on the breakout switch that were created on the server. Assign each access port that will link to the real switches into a different vlan. Each access port on the breakout switch now represents a router port e.g. fa0/6 in vlan 106 on the breakout switch represents router R6 fa0/0 interface which connects to Sw2 fa0/6.
Requirements:
1) A second network card
2) The vconfig utility.
apt-get install vlan
3) Kernel that will support Dot1q
modprobe 8021q
4) A breakout switch. Try to stick with a Cisco switch.
5) If you want to support QinQ / dot1q-tunnel, the breakout switch needs to support QinQ tunneling
Steps:
1) Create a trunk between your linux server and another switch that will become the switch in the middle or breakout switch.
2) Create the required vlans on the server. Or use the following script to do steps 1 and 2.
#!/bin/bash
#############
# vlansetup.sh
# http://21500.net
################# Enable Dot1q support
modprobe 8021q#### Set the ethernet MTU
ifconfig eth1 mtu 1536#### Create the Vlans
vconfig add eth1 101
vconfig add eth1 102
vconfig add eth1 103
vconfig add eth1 104
vconfig add eth1 105
vconfig add eth1 106
vconfig add eth1 107
vconfig add eth1 108
vconfig add eth1 109
vconfig add eth1 110
vconfig add eth1 111
vconfig add eth1 112
vconfig add eth1 113
vconfig add eth1 114
vconfig add eth1 115
vconfig add eth1 116
vconfig add eth1 117
vconfig add eth1 118
vconfig add eth1 119
vconfig add eth1 120
vconfig add eth1 121
vconfig add eth1 122
vconfig add eth1 123#### Bounce the interface
ifconfig eth1 down
ifconfig eth1 up
3) Configure the trunk on the breakout switch
interface fastethernet 0/24
switchport trunk encapsulation dot1q
switchport mode trunk
4) Assign the Access ports their vlans
!
interface fastethernet 0/1
switchport access vlan 101
switchport mode access
!
interface fastethernet 0/2
switchport access vlan 102
switchport mode access
!
interface fastethernet 0/3
switchport access vlan 103
switchport mode access
!
interface fastethernet 0/4
switchport access vlan 104
switchport mode access
! …
! …
! …
interface fastethernet 0/23
switchport access vlan 123
switchport mode access
!
5) If you want to support QinQ and CDP between the virtual routers and the real switchs, your breakout switch needs to support QinQ. Enable a dot1q tunnel on each interface.
interface range fastethernet 0/1 – 23
switchport mode dot1q-tunnel
l2protocol-tunnel cdp
6) Map the ports in the dynagen .net file
[[ROUTER R1]]
f0/0 = NIO_linux_eth:eth1.101
f0/1 = NIO_linux_eth:eth1.103
[[ROUTER R2]]
f1/0 = NIO_linux_eth:eth1.102
7) Connect the switches to the breakout switch with crossover cables. In this example Port fa0/1 on the breakout switch represents Fa0/0 on R1 and connects to Sw1 Fa0/1.
R1 Fa0/0 -> BSw Fa0/1 -> SW1 Fa0/1
R2 Fa1/0 -> BSw Fa0/2 -> SW1 Fa0/2
R1 Fa0/1 -> BSw Fa0/3 -> SW2 Fa0/1
Once I got this working I found that someone already did the hard work. Wish I saw this much earlier. The only difference between the two methods is that I used one breakout switch while MrPaul’s method uses the Dynamips switches and the breakout switch.
HOWTO Connect Real Switches Using One NIC & QinQ
This is the image MrPaul made:
