Lab with Cisco IOU

Cisco IOU (or Cisco IOL) is a version of IOS running on Linux. The advantage over using things like Dynamips/Dynagen is the better CPU usage. You can find more information about it on Jeremy Gaddis' FAQ.

Lab

This lab is quite simple. Two IOU instances and two Linux running BIRD are plugged on the same virtual switch and establish OSPF adjacencies between them (with BFD for faster convergence times).

IOU1>show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           1   FULL/BDR        00:00:39    192.0.2.1       Ethernet0/0
2.2.2.2           1   FULL/DR         00:00:39    192.0.2.2       Ethernet0/0
4.4.4.4           1   2WAY/DROTHER    00:00:34    192.0.2.4       Ethernet0/0

IOU1>show ip ospf rib

            OSPF Router with ID (3.3.3.3) (Process ID 1)


                Base Topology (MTID 0)

OSPF local RIB
Codes: * - Best, > - Installed in global RIB

*   192.0.2.0/24, Intra, cost 10, area 0, Connected
      via 192.0.2.3, Ethernet0/0
*>  198.51.100.101/32, Intra, cost 10, area 0
      via 192.0.2.1, Ethernet0/0
*>  198.51.100.102/32, Intra, cost 10, area 0
      via 192.0.2.2, Ethernet0/0
*   198.51.100.103/32, Intra, cost 1, area 0, Connected
      via 198.51.100.103, Loopback0
*>  198.51.100.104/32, Intra, cost 11, area 0
      via 192.0.2.4, Ethernet0/0

IOU1>show bfd neighbors

IPv4 Sessions
NeighAddr                              LD/RD         RH/RS     State     Int
192.0.2.1                               1/632309085  Up        Up        Et0/0
192.0.2.2                               2/2718792012 Up        Up        Et0/0

The transmit interval for BFD is 200 ms but it can be reduced on real hardware. It seems that on Cisco, only fully adjacent routers are using BFD.

Images

There is some duplicity when people talks about IOU. Only a few persons at Cisco are authorized to use it. However, if you search for Cisco IOU Collection, you should find something suitable on Bittorrent.

Once you have obtained your IOU images, link your favorite pick to images/i86bi-linux-l3.bin. Please note that older images may be missing a lot of features (for example, VLAN, port channels). More recent ones (15.x) are more likely to have the features you need. See Andrea Dainese's blog post for some details on this.

You may need to patch it if you get an error like this:

$ ../images/i86bi-linux-l3.bin --help
../images/i86bi-linux-l3.bin: error while loading shared libraries: libcrypto.so.4: cannot open shared object file: No such file or directory
$ sudo ln -s libcrypto.so.1.0.0 /usr/lib/i386-linux-gnu/libcrypto.so.4

You also need to update your ~/.iourc file. You may have downloaded a keygen.py script just for that.