A Few Words on Cabling
In our lab setups, we typically require several kinds of RJ-45 connections: rollover (Console), Ethernet crossover (X-over), and standard Ethernet straight-through cabling. For a reminder of the pin assignments, check Cisco.com (http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis3600/hw_inst/cabling/marcabl.htm).
Serial X-over cables are an entirely different matter due to the variety of interfaces. Again, refer to Cisco.com for details. Optical PCI ATM adapters can be connected back to back via a simple optical X-over cable pair without the need for an ATM switch. However, you will not be able to test network-to-network interface (NNI), switched virtual circuit (SVC), or interim local management interface (ILMI) features without an intermediary
Example 5-18. FreeBSD Bridge-Cluster Setup
[root@castor:~#] sysctl net.link.ether.bridge_cfg=vlan8:34,xl0:34,vlan9:35,xl1:35
[root@castor:~#] ifconfig vlan8 create
[root@castor:~#] ifconfig vlan9 create
[root@castor:~#] ifconfig vlan8 vlan 8 vlandev ed0
[root@castor:~#] ifconfig vlan9 vlan 9 vlandev ed0
You can certainly use advanced features such as filtering and traffic shaping on bridged interfaces, VLANs, and trunks as well
Example 5-16. Plain Bridging Between Two Interfaces
[root@castor:~#] sysctl net.link.ether.bridge=1
net.link.ether.bridge: 1 -> 1
[root@castor:~#] sysctl net.link.ether.bridge_cfg=xl0:1,ed0:1
net.link.ether.bridge_cfg: xl0:1 -> xl0:1,ed0:1
Example 5-17. FreeBSD Bridging-Related Status Information
[root@castor:~#] sysctl -a | grep bridge
net.link.ether.bridge_cfg: xl0:1,ed0:1
net.link.ether.bridge: 1
net.link.ether.bridge_ipfw: 0
net.link.ether.bridge_ipfw_drop: 0
net.link.ether.bridge_ipfw_collisions: 0
The configuration in Figure 5-3 and Example 5-18 is derived from the bridge(4) man page and presents a bridge-cluster setup example involving VLANs and parent interfaces. Interface ed0 acts as a VLAN trunk interface transporting VLANs 8 and 9. The sysctl configuration statement directs packets for VLAN 8 to physical interface xl0, and packets for VLAN 9 to xl1. The logical relationship is established by the two cluster identifiers that tie VLAN 8 to xl0 (cluster ID 34) and VLAN 9 to xl1 (cluster ID 35).
Lab 5-1: FreeBSD Bridge Cluster Lab
This lab introduces the FreeBSD approach to bridging. Bridging is available on OpenBSD and Linux as well; however, FreeBSD offers a unique feature named bridge-clusters. A cluster is an independent set of connected Ethernet or VLAN interfaces uniquely identified by a cluster ID. Consult the manual pages bridge(4), ng_bridge(4), vlan(4), and netgraph(4) for further details.
Example 5-16 shows the configuration sequence for bridging between two gateway interfaces (xl0 and ed0) via (default) cluster ID 1. Before we start, we have to turn bridging on via sysctl, however. The result of this configuration is presented in Example 5-17, the general concept in Figure 5-2.
Lab 5-2: Linux Bridging and the Spanning Tree
The Linux bridge administration is done via the brctl tool. Consult the man page for details and look at the Linux Bridge-STP-HOWTO (http/www.tldp.org/HOWTO/BRIDGE-STP-HOWTO/index.html) and http://bridge.sourceforge.net.
The following setup (Example 5-19) bridges between the two interfaces eth0 and eth1 of the callisto Linux gateway (setup and removal). Example 5-20 provides interface status information of the bridge setup, and Example 5-21 shows a more detailed experience with the brctl tool. Finally, Example 5-22 presents a short sniffer session to capture STP packets.
Example 5-19. Linux Bridge Configuration
[root@callisto:~#] brctl addbr mybridge
[root@callisto:~#] brctl addif mybridge eth0
[root@callisto:~#] brctl addif mybridge eth1
[root@callisto:~#] ifconfig mybridge up
[root@callisto:~#] ifconfig mybridge down
[root@callisto:~#] brctl delbr mybridge
Example 5-20. Linux Bridge Configuration Interface Status
