linux下打造雙網卡橋接

　　Name名稱

　　brctl - ethernet bridge administration brctl - 以太網橋管理

　　Synopsis簡介

　　brctl brctl

　　Description描述

　　brctl is used to set up, maintain, and inspect the ethernet bridge configuration in the linux kernel.brctl是用于建立，維護和檢查Linux內核的以太網橋配置研究。

　　An ethernet bridge is a device commonly used to connect different networks of ethernets together, so that these ethernets will appear as one ethernet to the participants.一個以太網是以太網橋設備以及常用的不同的網絡連接，使這些以太網將作為一個以太網的參與者。

　　Each of the ethernets being connected corresponds to one physical interface in the bridge.目前的以太網連接各對應一個物理接口的橋梁。 These individual ethernets are bundled into one bigger ('logical') ethernet, this bigger ethernet corresponds to the bridge network interface.這些個別以太網是以太網捆綁成一個更大的（'邏輯'）以太網，這對應于更大橋網絡接口。

　　Instances實例

　　The command brctl addbr creates a new instance of the ethernet bridge.該命令brctl addbr <名稱創建一個新的以太網橋的實例。 The network interface corresponding to the bridge will be called .該網絡接口對應的橋梁將被稱為<名稱。

　　The command brctl delbr deletes the instance of the ethernet bridge. <名稱>命令brctl delbr刪除以太網橋的實例<名稱。 The network interface corresponding to the bridge must be down before it can be deleted!該網絡接口對應的橋梁，必須下才能被刪除！

　　The command brctl show shows all current instances of the ethernet bridge.命令brctl顯示顯示當前所有的以太網橋的實例。

　　Ports端口

　　Each bridge has a number of ports attached to it.每個橋有一個連接到它的端口數。 Network traffic coming in on any of these ports will be forwarded to the other ports transparently, so that the bridge is invisible to the rest of the network (ie it will not show up in traceroute http://translate.googleusercontent.com/translate_c?hl=zh-CN&langpair=en%7Czh-CN&u=http://linux.die.net/man/8/traceroute&rurl=translate.google.com.hk&usg=ALkJrhgJakROF--e1An0sDTvEZMCZO7DQA> (8) ).未來的網絡流量在這些港口的任何會被轉發到其他港口透明，使無形的橋梁，是網絡的其余部分的（即它不會出現在了的traceroute （8））。

　　The command brctl addif
will make the interface a port of the bridge
.該命令brctl addif
將使接口 1
港口橋。 This means that all frames received on will be processed as if destined for the bridge.這意味著在收到的所有幀將被處理，好像注定了橋梁。 Also, when sending frames on
, will be considered as a potential output interface.此外，在發送
框架上，將被視為一個潛在的輸出接口。

　　The command brctl delif
will detach the interface from the bridge
.該命令brctl delif
將分離的橋梁
接口從。

　　The command brctl show
will show some information on the bridge and its attached ports.該命令將顯示brctl顯示
一些端口信息的橋梁及其附屬。

　　Ageing老齡化

　　The bridge keeps track of ethernet addresses seen on each port.這座橋的以太網保持跟蹤每個端口看到地址。 When it needs to forward a frame, and it happens to know on which port the destination ethernet address (specified in the frame) is located, it can 'cheat' by forwarding the frame to that port only, thus saving a lot of redundant copies and transmits.當它需要提出一個框架，它發生在哪個端口知道目標以太網地址（框架中指定）的位置，它可以'欺騙'的幀轉發到該端口只，從而節省了大量的冗余拷貝與傳輸。

　　However, the ethernet address location data is not static data.然而，以太網地址位置數據不是靜態數據。 Machines can move to other ports, network cards can be replaced (which changes the machine's ethernet address), etc.機器可以轉移到其他港口，網絡卡可以更換（從而改變了機器的以太網地址）等

　　brctl showmacs
shows a list of learned MAC addresses for this bridge. showmacs
brctl顯示的MAC地址列表獲悉此橋。

　　brctl setageingtime
sets the ethernet (MAC) address ageing time, in seconds. brctl setageingtime
<時間>設置MAC）地址老化時間，以秒以太網（。 After seconds of not having seen a frame coming from a certain address, the bridge will time out (delete) that address from the Forwarding DataBase (fdb).經過一定的地址<時間秒沒有看到一幀來自，橋梁將超時（刪除），解決從轉發數據庫（fdb）。

　　brctl setgcint
sets the garbage collection interval for the bridge
to seconds. brctl setgcint
<時間>設置為<時間間隔為秒的垃圾收集橋梁
。 This means that the bridge will check the forwarding database for timed out entries every seconds.這意味著，大橋將檢查<時間秒轉發數據庫超時每一個條目。

　　Spanning Tree Protocol生成樹協議

　　Multiple ethernet bridges can work together to create even larger networks of ethernets using the IEEE 802.1d spanning tree protocol.多個以太網橋可以共同創造更大的網絡，以太網使用IEEE 802.1D生成樹協議。 This protocol is used for finding the shortest path between two ethernets, and for eliminating loops from the topology.這個協議是用來找出兩個以太網之間的 短路徑，拓撲結構和消除循環的。 As this protocol is a standard, linux bridges will interwork properly with other third party bridge products.由于此協議是一個標準，Linux的橋梁將妥善互通的橋梁與其他第三方產品。 Bridges communicate with eachother by sending and receiving BPDUs (Bridge Protocol Data Units).橋梁溝通海誓山盟通過發送和接收BPDUs訊息（橋協議數據單元）。 These BPDUs can be recognised by an ethernet destination address of 01:80:c2:00:00:00.這些BPDUs訊息可識別以太網目標地址的01:80：c2的：00:00:00。

　　The spanning tree protocol can also be turned off (for those situations where it just doesn't make sense, for example when this linux box is the only bridge on the LAN, or when you know that there are no loops in the topology.)生成樹協議還可以關閉意識（對于那些情況下它只是不作，例如在Linux機器這是唯一的橋梁，或當在局域網上，你知道，有沒有循環中的拓撲。）

　　brctl (8) can be used for configuring certain spanning tree protocol parameters. brctl（8）可用于配置某些生成樹協議參數。 For an explanation of these parameters, see the IEEE 802.1d specification (or send me an email).對于這些參數的解釋，看到了IEEE 802.1d的規格（或向我發送電子郵件）。 The default values should be just fine.默認值應該只是罰款。 If you don't know what these parameters mean, you probably won't feel the desire to tweak them.如果你不知道這些參數的意思是，你可能不會覺得他們的愿望來調整。

　　brctl stp <bridge> <state> controls this bridge instance's participation in the spanning tree protocol. brctl污水處理廠<bridge> <state>控制此橋實例的協議參與生成樹。 If <state> is "on" or "yes" the STP will be turned on, otherwise it will be turned off.如果<state>是“開”或“是”的污水處理廠將被打開，否則將被關閉。 When turned off, the bridge will not send or receive BPDUs, and will thus not participate in the spanning tree protocol.當關閉時，橋將不會發送或接收BPDUs訊息，并因此不參與生成樹協議。 If your bridge isn't the only bridge on the LAN, or if there are loops in the LAN's topology, DO NOT turn this option off.如果你的橋是不是在局域網上的唯一橋梁，或者有在局域網的拓撲結構的循環，不要關閉此選項。 If you turn this option off, please know what you are doing.如果你關閉此選項，請知道自己在做什么。

　　brctl setbridgeprio <bridge> <priority> sets the bridge's priority to <priority>. brctl setbridgeprio <bridge> <priority>設置橋的優先<priority>。 The priority value is an unsigned 16-bit quantity (a number between 0 and 65535), and has no dimension.優先級值是一個無符號16位的數量（1 0和65535之間的數字），沒有任何方面。 Lower priority values are 'better'.低優先級值是'好'。 The bridge with the lowest priority will be elected 'root bridge'. 低的優先大橋將是當選'根橋'。

　　brctl setfd <bridge> <time> sets the bridge's 'bridge forward delay' to <time> seconds. brctl setfd <bridge> <時間>設置橋梁的'橋向前延遲'來<時間秒。

　　brctl sethello <bridge> <time> sets the bridge's 'bridge hello time' to <time> seconds. brctl sethello <bridge> <時間>設置橋梁的'橋你好時間'來<時間秒。

　　brctl setmaxage <bridge> <time> sets the bridge's 'maximum message age' to <time> seconds. brctl setmaxage <bridge> <時間>設置橋梁的'年齡 大的信息'來<時間秒。

　　brctl setpathcost <bridge> <port> <cost> sets the port cost of the port <port> to <cost>. brctl setpathcost <bridge> <端口<cost>設置端口<端口端口的成本為<cost>。 This is a dimensionless metric.這是一個無量綱指標。

　　brctl setportprio <bridge> <port> <priority> sets the port <port>'s priority to <priority>. brctl setportprio <bridge> <端口<priority>設置端口<端口的優先<priority>。 The priority value is an unsigned 8-bit quantity (a number between 0 and 255), and has no dimension.優先級值是一個無符號8位的數量（0至255個號碼和），并沒有尺寸。 This metric is used in the designated port and root port selection algorithms.該指標用于在指定端口和根端口選擇算法。