Linux Network Bridge

Linux Network Bridge operations-Linux Enterprise Application-Linux server application information, the following is a detailed description. 1. Set

L obtain ''bridge configuration''
Ftp://shadow.cabi.net/pub/Linux/BRCFG.tgz
L obtain and read ''multiple ethernet ''HOWTO
Ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/mini/Multiple-Ethernet
L Configure lilo startup parameters
Make multiple Ethernet devices operate on your machine and add them to your/etc/lilo. conf and re-Execute lilo: append = "ether =, eth1"
If you have three interfaces on your bridge, use these lines to replace the above
Append = "ether =, eth1 ether =, eth2"
You can find more interfaces by adding more tlab statements. by default, a traditional Linux core detects only one unique ethernet card and stops when one is found. the statement attached above tells the core to continue to detect more Ethernet devices after the first device is found.
Another way is to replace the following variables with startup variables:
Linux ether = 0, 0, eth1
Alternatively, you can use the following three interfaces:
Linux ether = 0, 0, eth1 ether = 0, eth2
L re-compile the core to start the BRIDGING function
L there should be no IP address for a bridge. it can have one, but a common bridge does not need an IP address. remove IP addresses from your bridge to/etc/sysconfig/network-scripts/(for a RedHat system) and copy ifcfg-lo0 to ifcfg-eth0 & ifcfg-eth1. in the two tlab files, the line changed contains ''device = lo'' to ''device = eth0'' and ''device = eth1 ''. other Linux distribution may be different from this. You can do what you want! If there are more than two interfaces on the bridge, make sure that the settings match these interfaces.
L restart, execute the core that contains the bridge function, and confirm that an IP address is not specified to this network interface.
L once the system is backed up, the ethernet card of Ethernet is set in the chaotic mode. They will monitor each packet through its interface:
Ifconfig promisc eth0; ifconfig promisc eth1
All interfaces connected to the network segment are separated by the bridge to enter the promiscuous mode.
L start the bridge and use the brcfg program:
Brcfg? Ena
L verify that each interface has different traffic flows:
Tcpdump-I eth0 (in a window)
Tcpdump-I eth1 (in another window)
Execute an sniffer or tcpdump to verify that the bridge adapter correctly separates the segments on another machine.

　　 2. General Problems

L Question: I get this message ioctl (SIOCGIFBR) failed: Package not installed what does this mean?
L Answer: Your core does not have the ability to Bridge. Get a 2.0 or later core, and recompile the option BRIDGING to start the bridge function.
L Question: the machine cannot be pinged to the other side!
L Answer: Do you use ''brcfg-ename' to enable the bridge adapter to operate? (Brcfg will say ''bridging is ENABLED '') Do you have to place the interface in the promiscuous (chaotic) mode? (Use the ''ifconfig'' command. Then the ''promisc' parameter should be on two interfaces .). If you are using the multiple-media interface, make sure that the end is started correctly. You may need to use the configuration/setup program attached to the network interface for configuration.
L Question: I cannot telnet/ftp from the bridge! Why?
L Answer: this is because no IP address is specified to the interface of any bridge adapter. A bridge is the transparent part of a network.
L Question: What do I need to do to set routes?
L Answer: none! The entire routing data is controlled by the core bridge adapter code. The bridge adapter can see that the ethernet address is learned. In the test error mode, use the brcfg program: brcfg? Deb
L Question: the bridge seems to work, but why doesn't ''traceroute' show that the bridge is a part of the path?
L Answer: Due to the functionality of the bridge adapter, ''traceroute'' does not display the bridge as part of the path. A bridge is a transparent component of the network.
L Question: Does IP_FORWARD need to be compiled into the core?
L Answer: No. The code of the bridge in the core takes care of packet transfer. IP_FORWARD has an IP address specified for a gateway.
L Question: According to the ''brcfg ''program, why is the ethernet address of Port 1 and Port 2 the same? Should they be different?
L Answer: No. Each port of a bridge adapter is intentionally directed by the bridge adapter code to specify the ethernet address of the same entity.
L Question: when a make config build setting is executed in the core, the bridging option does not appear. How does it start? What's wrong? Br> l Answer: during core configuration, Answer the following questions: 'y', ''Prompt for development and/or incomplete code/drivers (CONFIG_EXPERIMENTAL) [Y/n/?] ''.
L Question: too many hubs (four or more) are connected one by one (consecutively) on a Ethernet to cause time response problems. what will happen to a bridge in a subnet built by a hub?
L Answer: resets the 3/4/5 hub rule for a bridge. A bridge does not process packets as a hub, so no contributor (contributor) has time to respond to problems on a network.
L Question: can a bridge interface connect both 10 Mb and 100 Mb Ethernet segments? Will this configuration slow the Other Side of high-speed traffic?
L Answer: Yes. A bridge adapter can bind a 10 Mb block with a 100 Mb block. As long as the network is stuck on the side of the fast network of the bridge adapter, it has the capability of 100 Mb, TCP will take care of the remaining parts. at this time, it occurs that one host on the 100 Mb network sends packets to communicate with the other host on the 10 Mb network, only moving at 10 Mb/s speed, the remaining network traffic will not be slowed down in the fast network.