Internet Engineering Task Force (IETF) R. Perlman
Request for Comments: 6439 Intel Labs
Updates: 6325 D. Eastlake 3rd
Category: Standards Track Y. Li
ISSN: 2070-1721 Huawei Technologies
A. Banerjee
Cisco Systems
F. Hu
ZTE Corporation
November 2011
Internet Engineering Task Force (IETF) R. Perlman
Request for Comments: 6439 Intel Labs
Updates: 6325 D. Eastlake 3rd
Category: Standards Track Y. Li
ISSN: 2070-1721 Huawei Technologies
A. Banerjee
Cisco Systems
F. Hu
ZTE Corporation
November 2011
Routing Bridges (RBridges): Appointed Forwarders
路由桥（RBridges）：指定的货运代理
Abstract
摘要
The IETF TRILL (TRansparent Interconnection of Lots of Links) protocol provides least cost pair-wise data forwarding without configuration in multi-hop networks with arbitrary topology, safe forwarding even during periods of temporary loops, and support for multipathing of both unicast and multicast traffic. TRILL accomplishes this by using IS-IS (Intermediate System to Intermediate System) link state routing and by encapsulating traffic using a header that includes a hop count. Devices that implement TRILL are called "RBridges" (Routing Bridges).
IETF TRILL（多链路透明互连）协议在具有任意拓扑结构的多跳网络中提供无需配置的最低成本成对数据转发，即使在临时环路期间也能安全转发，并支持单播和多播流量的多路径传输。TRILL通过使用IS-IS（中间系统到中间系统）链路状态路由和使用包含跃点计数的报头封装流量来实现这一点。实现TRILL的设备称为“RBridges”（路由桥）。
TRILL supports multi-access LAN (Local Area Network) links that can have multiple end stations and RBridges attached. Where multiple RBridges are attached to a link, native traffic to and from end stations on that link is handled by a subset of those RBridges called "Appointed Forwarders", with the intent that native traffic in each VLAN (Virtual LAN) be handled by at most one RBridge. The purpose of this document is to improve the documentation of the Appointed Forwarder mechanism; thus, it updates RFC 6325.
TRILL支持可以连接多个终端站和RBridge的多址LAN（局域网）链路。当多个RBridge连接到一条链路时，与该链路上的终端站之间的本机通信由这些RBridge的子集（称为“指定转发器”）处理，目的是每个VLAN（虚拟LAN）中的本机通信最多由一个RBridge处理。本文件旨在改进指定货运代理机制的文件编制；因此，它更新了RFC6325。
Status of This Memo
关于下段备忘
This is an Internet Standards Track document.
这是一份互联网标准跟踪文件。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。有关互联网标准的更多信息，请参见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6439.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc6439.
Copyright Notice
版权公告
Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2011 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction ....................................................2
1.1. Terminology and Acronyms ...................................3
2. Appointed Forwarders and Their Appointment ......................4
2.1. Appointment Effects of DRB Elections .......................5
2.2. Appointment and Removal by the DRB .........................5
2.2.1. Processing Forwarder Appointments ...................6
2.2.2. Frequency of Appointments ...........................7
2.2.3. Appointed Forwarders Limit ..........................8
2.3. Local Configuration Action Appointment Effects .............8
2.4. VLAN Mapping within a Link .................................9
3. The Inhibition Mechanism ........................................9
4. Inhibited Appointed Forwarder Behavior .........................11
5. Multiple Ports on the Same Link ................................12
6. Security Considerations ........................................12
7. Acknowledgements ...............................................13
8. References .....................................................13
8.1. Normative References ......................................13
8.2. Informative References ....................................13
Appendix. VLAN Inhibition Example .................................14
1. Introduction ....................................................2
1.1. Terminology and Acronyms ...................................3
2. Appointed Forwarders and Their Appointment ......................4
2.1. Appointment Effects of DRB Elections .......................5
2.2. Appointment and Removal by the DRB .........................5
2.2.1. Processing Forwarder Appointments ...................6
2.2.2. Frequency of Appointments ...........................7
2.2.3. Appointed Forwarders Limit ..........................8
2.3. Local Configuration Action Appointment Effects .............8
2.4. VLAN Mapping within a Link .................................9
3. The Inhibition Mechanism ........................................9
4. Inhibited Appointed Forwarder Behavior .........................11
5. Multiple Ports on the Same Link ................................12
6. Security Considerations ........................................12
7. Acknowledgements ...............................................13
8. References .....................................................13
8.1. Normative References ......................................13
8.2. Informative References ....................................13
Appendix. VLAN Inhibition Example .................................14
The IETF TRILL (TRansparent Interconnection of Lots of Links) protocol [RFC6325] provides optimal pair-wise data frame forwarding without configuration in multi-hop networks with arbitrary topology, safe forwarding even during periods of temporary loops, and support for multipathing of both unicast and multicast traffic. TRILL accomplishes this by using IS-IS (Intermediate System to Intermediate System) [IS-IS] [RFC1195] link state routing and encapsulating traffic using a header that includes a hop count. The design
IETF TRILL（大量链路的透明互连）协议[RFC6325]在具有任意拓扑结构的多跳网络中提供无需配置的最佳成对数据帧转发，即使在临时循环期间也能安全转发，并支持单播和多播流量的多路径传输。TRILL通过使用IS-IS（中间系统到中间系统）[IS-IS][RFC1195]链路状态路由和使用包含跃点计数的报头封装流量来实现这一点。设计
supports VLANs (Virtual Local Area Networks) and optimization of the distribution of multi-destination frames based on VLANs and IP-derived multicast groups. Devices that implement TRILL are called "RBridges" (Routing Bridges).
支持VLAN（虚拟局域网）和基于VLAN和IP派生的多播组优化多目标帧的分布。实现TRILL的设备称为“RBridges”（路由桥）。
Section 2 of [RFC6327] explains the environment for which the TRILL protocol is designed and the differences between that environment and the typical Layer 3 routing environment.
[RFC6327]的第2节解释了TRILL协议的设计环境以及该环境与典型的第3层路由环境之间的差异。
TRILL supports multi-access LAN (Local Area Network) links that can have multiple end stations and RBridges attached. Where multiple RBridges are attached to a link, native traffic to and from end stations on that link is handled by a subset of those RBridges called "Appointed Forwarders", with the intent that native traffic in each VLAN be handled by at most one RBridge. An RBridge can be Appointed Forwarder for many VLANs.
TRILL支持可以连接多个终端站和RBridge的多址LAN（局域网）链路。当多个RBridge连接到一条链路时，往返该链路上终端站的本机流量由这些RBridge的子集（称为“指定转发器”）处理，目的是每个VLAN中的本机流量最多由一个RBridge处理。RBridge可以被指定为许多VLAN的转发器。
The purpose of this document is to improve the documentation of the Appointed Forwarder mechanism; thus, it updates RFC 6325. It includes reference implementation details. Alternative implementations that interoperate on the wire are permitted.
本文件旨在改进指定货运代理机制的文件编制；因此，它更新了RFC6325。它包括参考实现细节。允许在线路上进行互操作的替代实现。
The Appointed Forwarder mechanism is irrelevant to any link on which end station service is not offered. This includes links configured as point-to-point IS-IS links and any link with all RBridge ports on that link configured as trunk ports. (In TRILL, configuration of a port as a "trunk port" just means that no end station service will be provided. It does not imply that all VLANs are enabled on that port.)
指定的转发器机制与未提供终端站服务的任何链路无关。这包括配置为点到点IS链路的链路以及该链路上所有RBridge端口配置为中继端口的任何链路。（在TRILL中，将端口配置为“中继端口”只意味着不提供终端站服务。这并不意味着在该端口上启用了所有VLAN。）
The Appointed Forwarder mechanism has no effect on the formation of adjacencies, the election of the Designated RBridge (DRB) for a link, MTU matching, or pseudonode formation. Those topics are covered in [RFC6327]. Furthermore, Appointed Forwarder status has no effect on the forwarding of TRILL Data frames. It only affects the handling of native frames.
指定的转发器机制对邻接的形成、为链路选择指定的RBridge（DRB）、MTU匹配或伪节点形成没有影响。[RFC6327]中介绍了这些主题。此外，指定的转发器状态对TRILL数据帧的转发没有影响。它只影响本机帧的处理。
For other aspects of the TRILL base protocol, see [RFC6325] and [RFC6327]. Familiarity with [RFC6325] and [RFC6327] is assumed in this document. In case of conflict between this document and [RFC6325], this document prevails.
有关TRILL基本协议的其他方面，请参见[RFC6325]和[RFC6327]。本文件假定熟悉[RFC6325]和[RFC6327]。如果本文件与[RFC6325]之间存在冲突，则以本文件为准。
This document uses the acronyms defined in [RFC6325].
本文件使用[RFC6325]中定义的首字母缩略词。
A "trunk port" is a port configured with the "end station service disable" bit on, as described in Section 4.9.1 of [RFC6325].
“中继端口”是一个配置了“终端站服务禁用”位的端口，如[RFC6325]第4.9.1节所述。
In this document, the term "link" means "bridged LAN", that is to say some combination of physical links with zero or more bridges, hubs, repeaters, or the like.
在本文档中，术语“链路”表示“桥接LAN”，即具有零个或多个网桥、集线器、中继器等的物理链路的某种组合。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“建议”、“不建议”、“可”和“可选”应按照[RFC2119]中的说明进行解释。
The Appointed Forwarder on a link for VLAN-x is the RBridge that ingresses native frames from the link and egresses native frames to the link in VLAN-x. By default, the DRB (Designated RBridge) on a link is in charge of native traffic for all VLANs on the link. The DRB may, if it wishes, act as Appointed Forwarder for any VLAN and it may appoint other RBridges that have ports on the link as Appointed Forwarder for one or more VLANs.
VLAN-x链路上指定的转发器是RBridge，它从链路进入本机帧，并将本机帧出口到VLAN-x中的链路。默认情况下，链路上的DRB（指定为RBridge）负责链路上所有VLAN的本机流量。如果DRB愿意，可以作为任何VLAN的指定转发器，也可以指定链路上有端口的其他RBridge作为一个或多个VLAN的指定转发器。
It is important that there not be two Appointed Forwarders on a link that are ingressing and egressing native frames for the same VLAN at the same time. Should this occur, it could form a loop where frames are not protected by a TRILL Hop Count for part of the loop. (Such a condition can even occur through two Appointed Forwarders for two different VLANs, VLAN-x and VLAN-y, if ports or bridges inside the link are configured to map frames between VLAN-x and VLAN-y as discussed in Section 2.4.) While TRILL tries to avoid such situations, for loop safety there is also an "inhibition" mechanism (see Section 3) that can cause an RBridge that is an Appointed Forwarder to not ingress or egress native frames.
重要的是，链路上不能有两个指定的转发器同时进入和退出同一VLAN的本机帧。如果出现这种情况，它可能会形成一个循环，其中部分循环的帧不受颤音跳数的保护。（如果链路内的端口或网桥配置为映射VLAN-x和VLAN-y之间的帧（如第2.4节所述），则这种情况甚至可以通过两个不同VLAN（VLAN-x和VLAN-y）的指定转发器发生。）当TRILL试图避免这种情况时，为了环路安全，还有一种“抑制”机制（见第3节）这可能导致作为指定转发器的RBridge无法进入或退出本机帧。
As discussed in Section 5, an RBridge may have multiple ports on a link. As discussed in [RFC6327], if there are multiple ports with the same Media Access Control (MAC) address on a link, all but one will be suspended. The case of multiple ports on a link for one RBridge and the case of multiple ports with the same MAC address on a link and combinations of these cases are fully accommodated; however, multiple ports on a link for one RBridge is expected to be a rare condition and duplicate MAC addresses are not recommended by either TRILL or IEEE 802.1 standards.
如第5节所述，RBridge在链路上可能有多个端口。如[RFC6327]中所述，如果链路上有多个具有相同媒体访问控制（MAC）地址的端口，则除一个端口外，所有端口都将挂起。一个RBridge的链路上有多个端口的情况以及链路上有多个具有相同MAC地址的端口的情况以及这些情况的组合都得到了充分考虑；然而，对于一个RBridge，链路上的多个端口预计是一种罕见的情况，TRILL或IEEE 802.1标准都不建议使用重复的MAC地址。
Appointed Forwarder status has no effect on the forwarding of TRILL Data frames. It only affects the handling of native frames.
指定的转发器状态对TRILL数据帧的转发没有影响。它只影响本机帧的处理。
There are three mechanisms by which an RBridge can be appointed or un-appointed as Appointed Forwarder: as a result of the DRB elections [RFC6327] as discussed in Section 2.1, as a result of action by the DRB as discussed in Section 2.2, as a result of a local configuration action as discussed in Section 2.3.
有三种机制可以任命或取消任命RBridge为指定的货运代理：第2.1节讨论的DRB选举[RFC6327]的结果，第2.2节讨论的DRB行动的结果，第2.3节讨论的本地配置行动的结果。
When an RBridge believes that it has become the DRB on a link, by default, it can act as Appointed Forwarder for any VLANs on that link that it chooses as long as its port is not configured as a trunk port and has that VLAN enabled (or at least one of its ports meets these criteria, if it has more than one port on the link).
当RBridge认为自己已成为链路上的DRB时，默认情况下，只要其端口未配置为中继端口且已启用该VLAN（或者至少有一个端口满足这些标准，如果链路上有多个端口），它就可以充当该链路上所选任何VLAN的指定转发器。
An RBridge loses all Appointed Forwarder status when:
在以下情况下，RBridge将失去所有指定的货运代理状态：
1. it decides that it has lost the status of being the DRB for a link; or
1. 它决定它已失去作为链路的DRB的状态；或
2. it observes a change in the RBridge that is the DRB for the link without itself becoming the DRB.
2. 它观察到作为链路的DRB的RBridge中的变化，而自身不会成为DRB。
In the rare corner case where an RBridge has more than one port on a link, one of which was previously the DRB election winner but has just lost the DRB election to a different port of the same RBridge (possibly due to management configuration of port priorities), there is no change in which RBridge is the DRB. Therefore, neither of the above points applies and there is no change in Appointed Forwarder status.
在罕见的情况下，如果RBridge在链路上有多个端口，其中一个以前是DRB选举的获胜者，但刚刚失去DRB选举到同一RBridge的另一个端口（可能是由于端口优先级的管理配置），则RBridge是DRB的情况没有变化。因此，上述各点均不适用，且指定货代的状态没有变化。
The DRB may appoint other RBridges on the link through inclusion of one or more Appointed Forwarders sub-TLVs [RFC6326] in a TRILL Hello it sends on the Designated VLAN out the port that won the DRB election. When the DRB sends any appointments in a TRILL Hello, it must send all appointments for that link in that Hello. Any previous appointment not included is implicitly revoked.
DRB可以通过将一个或多个指定的转发器子TLV[RFC6326]包含在TRILL Hello中，从而在链路上指定其他RBridge，该转发器子TLV[RFC6326]在指定VLAN上从赢得DRB选举的端口发送出去。当DRB在TRILL Hello中发送任何约会时，它必须在该Hello中发送该链接的所有约会。未包括的任何先前任命都将被隐式撤销。
Although the DRB does not need to announce the VLANs for which it has chosen to act as Appointed Forwarder by sending appoints for itself, if the DRB wishes to revoke all appointments for RBridges other than itself on the link, it is recommended that it send a TRILL Hello with an appointment for itself for some VLAN.
尽管DRB不需要通过发送自己的任命来宣布其选择作为指定转发器的VLAN，但如果DRB希望撤销链路上RBridge以外的所有任命，建议其发送TRILL Hello，并为某些VLAN发送自己的任命。
The DRB MUST NOT send any appointments on a link unless its DRB inhibition timer (see Section 3) for that link is expired.
DRB不得在链路上发送任何约会，除非该链路的DRB抑制计时器（见第3节）过期。
How the DRB decides what other RBridges on the link, if any, to appoint forwarder for which VLANs is beyond the scope of this document.
DRB如何决定链路上的哪些其他RBridge（如果有），以指定VLAN超出本文档范围的转发器。
When a non-DRB RBridge that can offer end station service on a link receives a TRILL Hello that is not discarded for one of the reasons given in [RFC6327], it checks the source MAC address and the Port ID and System ID in the Hello to determine if it is from the winning DRB port. If it is not from that port, any Appointed Forwarder sub-TLVs in the Hello are ignored, and there is no change in the receiving RBridge's Appointed Forwarder status. Also, if no Appointed Forwarder sub-TLVs are present in the TRILL Hello, there is no change in the receiver's Appointed Forwarder status.
当能够在链路上提供终端站服务的非DRB RBridge收到由于[RFC6327]中给出的原因之一而未被丢弃的TRILL Hello时，它会检查Hello中的源MAC地址、端口ID和系统ID，以确定它是否来自获胜的DRB端口。如果不是来自该端口，则忽略Hello中的任何指定转发器子TLV，并且接收RBridge的指定转发器状态没有更改。此外，如果TRILL Hello中没有指定的转发器子TLV，则接收方的指定转发器状态没有变化。
However, if the TRILL Hello is from the winning DRB port and the Hello includes one or more Appointed Forwarder sub-TLVs, then the receiving RBridge becomes appointed for the VLANs that are both listed for it in the Hello and are enabled on the receiving port. (If the appointment includes VLAN IDs 0x000 or 0xFFF, they are ignored, but any other VLAN IDs are still effective.) If the receiver was Appointed Forwarder for any other VLANs, its Appointed Forwarder status for such other VLANs is revoked. For example, if none of these sub-TLVs in a Hello appoints the receiving RBridge, then it loses all Appointed Forwarder status and is no longer Appointed Forwarder for any VLAN on the port where the Hello was received.
但是，如果TRILL Hello来自获胜的DRB端口，并且Hello包括一个或多个指定的转发器子TLV，则接收RBridge将被指定用于VLAN，VLAN在Hello中列出，并在接收端口上启用。（如果指定包括VLAN ID 0x000或0xFFF，则忽略它们，但任何其他VLAN ID仍然有效。）如果接收器被指定为任何其他VLAN的转发器，则其针对此类其他VLAN的指定转发器状态被撤销。例如，如果Hello中的这些子TLV都没有指定接收RBridge，那么它将丢失所有指定的转发器状态，并且不再是接收Hello的端口上任何VLAN的指定转发器。
The handling of one or more Appointed Forwarder sub-TLVs in a Hello from the winning port that appoints the receiving RBridge is as follows. An appointment in an Appointed Forwarder sub-TLV is for a specific RBridge and a contiguous interval of VLAN IDs; however, as stated above, it actually appoints that RBridge forwarder only for the VLAN(s) in that range that are enabled on one or more ports that RBridge has on the link (ignoring any ports configured as trunk ports or as IS-IS point-to-point ports). If the RBridge was Appointed Forwarder for any additional VLANs beyond the VLANs for which it was being appointed, it loses Appointed Forwarder status for such additional VLANs.
指定接收RBridge的获胜港口在Hello中处理一个或多个指定货代子TLV如下。指定转发器子TLV中的指定用于特定RBridge和VLAN ID的连续间隔；但是，如上所述，它实际上只为该范围内的VLAN指定RBridge转发器，这些VLAN在RBridge在链路上的一个或多个端口上启用（忽略任何配置为中继端口或IS点到点端口的端口）。如果RBridge被指定为超出其被指定VLAN范围的任何其他VLAN的转发器，则它将丢失此类其他VLAN的指定转发器状态。
There is no reason for an RBridge to remember that it received a valid appointment message for a VLAN that was ineffective because the VLAN was not enabled on the port where the message was received or because the port was a trunk or point-to-point port. It does not become Appointed Forwarder for such a VLAN just because that VLAN is later enabled or the port later reconfigured.
RBridge没有理由记住，它收到的VLAN的有效约会消息无效，因为接收消息的端口上未启用VLAN，或者端口是中继或点对点端口。它不会因为VLAN稍后启用或端口稍后重新配置而成为此类VLAN的指定转发器。
It should be straightforward for the DRB to send, within one Hello, the appointments for several dozen VLAN IDs or several dozen blocks of contiguous VLAN IDs. Should the VLANs the DRB wishes to appoint be inconveniently distributed, for example, the proverbial case where the DRB RB1 wishes to appoint RB2 forwarder for all even-numbered VLANs and appoint RB3 forwarder for all odd-numbered VLANs, the following method may be used. The network manager normally controls what VLANs are enabled on RBridge port. Thus, the network manager can appoint an RBridge forwarder for an arbitrary set of scattered VLANs by enabling only those VLANs on the relevant port (or ports) and then having the DRB send an appointment that appears to appoint the target RBridge forwarder for all VLANs. However, for proper operation and inter-RBridge communication, the Designated VLAN for a link SHOULD be enabled on all RBridge ports on that link, and it may not be desired to appoint the RBridge forwarder for the Designated VLAN. Thus, in the general case, it would require two appointments, although it would still only require one appointment if the Designated VLAN were an extreme low or high value such as VLAN 0xFFE or the default VLAN 1.
DRB在一个Hello内发送几十个VLAN ID或几十个连续VLAN ID块的预约应该很简单。如果DRB希望指定的VLAN分布不方便，例如，众所周知，DRB RB1希望为所有偶数VLAN指定RB2转发器，并为所有奇数VLAN指定RB3转发器，则可以使用以下方法。网络管理器通常控制在RBridge端口上启用的VLAN。因此，网络管理器可以通过仅启用相关端口（或多个端口）上的那些VLAN，然后让DRB发送似乎为所有VLAN指定目标RBridge转发器的预约，为任意分散的VLAN集指定RBridge转发器。但是，为了正确操作和RBridge间通信，应在该链路上的所有RBridge端口上启用链路的指定VLAN，并且可能不希望为指定VLAN指定RBridge转发器。因此，在一般情况下，它将需要两次预约，尽管如果指定的VLAN是极低或极高的值，例如VLAN 0xFFE或默认VLAN 1，它仍然只需要一次预约。
For example, assume the DRB wants RB2 to be Appointed Forwarder for all even-numbered VLANs and the Designated VLAN for the link is VLAN 101. The network manager could cause all even-numbered VLANs plus VLAN 101 to be enabled on the relevant port of RB2 and then, with the desired effect, cause the DRB to send appointments to RB2 appointing it forwarder for all VLANs from 1 through 100 and from 102 through 4,094.
例如，假设DRB希望RB2被指定为所有偶数VLAN的转发器，并且链路的指定VLAN是VLAN 101。网络管理器可以在RB2的相关端口上启用所有偶数编号的VLAN加上VLAN 101，然后，在期望的效果下，使DRB向RB2发送预约，为从1到100以及从102到4094的所有VLAN指定it转发器。
Should the network manager have misconfigured the enabled VLANs and Appointed Forwarders, resulting in two RBridges believing they are Appointed Forwarders for the same VLAN, then item 4 in Section 3 will cause one or more of the RBridges to be inhibited for that VLAN.
如果网络管理器错误配置了启用的VLAN和指定转发器，导致两个RBridge认为它们是同一VLAN的指定转发器，则第3节中的第4项将导致该VLAN的一个或多个RBridge被禁用。
It is not necessary for the DRB to include the forwarder appointments in every TRILL Hello that it sends on the Designated VLAN for a link. For loop safety, every RBridge is required to indicate, in every TRILL Hello it sends in VLAN-x on a link, whether it is an Appointed Forwarder for VLAN-x for that link (see item 4 in Section 3). It is also RECOMMENDED that the DRB have all VLANs for which end station service will be offered on the link as well as the Designated VLAN, enabled. Thus, the DRB will generally be informed by other RBridges on the link of the VLANs for which they believe they are Appointed Forwarder. If this matches the appointments the DRB wishes to make, it is not required to re-send its forwarder appointments; however, for robustness, especially in cases such as VLAN misconfigurations in
DRB没有必要在其为链路在指定VLAN上发送的每个TRILL Hello中包含转发器预约。为了环路安全，要求每个RBridge在其在链路上以VLAN-x发送的每个TRILL Hello中指示它是否是该链路VLAN-x的指定转发器（参见第3节中的第4项）。还建议DRB启用链路上提供终端站服务的所有VLAN以及指定的VLAN。因此，DRB通常会收到VLAN链路上的其他RBridge的通知，他们认为自己是VLAN的指定转发器。如果这与DRB希望作出的任命相符，则无需重新发送其货运代理人任命；但是，对于健壮性，尤其是在中的VLAN配置错误等情况下
a bridged LAN link, it is RECOMMENDED that the DRB send its forwarder appointments on the Designated VLAN at least once per its Holding Time on the port that won the DRB election.
作为桥接LAN链路，建议DRB在赢得DRB选举的端口上，每等待一次，至少在指定VLAN上发送一次其转发器预约。
The mechanism of DRB forwarder appointment and the limited length of TRILL Hellos impose a limit on the number of RBridges on a link that can be Appointed Forwarders. To obtain a conservative estimate, assume that no more than 1000 bytes are available in a TRILL Hello for such appointments. Assume it is desired to appoint various RBridges on a link forwarder for arbitrary non-intersecting sets of VLANs. Using the technique discussed above would generally require two appointments, or 12 bytes, per RBridge. With allowance for sub-TLV and TLV overhead, appointments for 83 RBridges would fit in under 1000 bytes. Including the DRB, this implies a link with 84 or more RBridges attached. Links with more than a handful of RBridges attached are expected to be rare.
DRB转发器任命机制和TRILL Hellos的有限长度限制了链路上可指定转发器的RBridge数量。为获得保守估计，假设此类预约的颤音Hello中可用字节数不超过1000字节。假设需要在链路转发器上为任意非交叉VLAN集指定各种RBridge。使用上面讨论的技术通常需要两次预约，即每个RBridge需要12个字节。考虑到子TLV和TLV开销，83个RBridge的预约将在1000字节以下。包括DRB，这意味着连接了84个或更多RBB的链路。与多个RBridge连接的链接预计将很少见。
Note: If the Designated VLAN were an extreme low or high value, such as VLAN 1, which is the default and may be a common value in practice, only 6 bytes per RBridge would be required. This would permit twice as many different Appointed Forwarder RBridges than indicated by the general analysis above or, alternatively, would take only half as much space to appoint the same number of Appointed Forwarders.
注意：如果指定的VLAN是一个极低或极高的值，例如VLAN 1，这是默认值，在实践中可能是一个公共值，那么每个RBridge只需要6个字节。这将允许两倍于上述一般分析所示数量的不同指定货运代理，或者只需要一半的空间来指定相同数量的指定货运代理。
Unnecessary changes in Appointed Forwarders SHOULD NOT be made as they may result in transient lack of end station service. Large numbers of Appointed Forwarders on a link (in excess of 65) are NOT RECOMMENDED due to the complexity of their establishment and maintenance.
不应对指定的货运代理进行不必要的变更，因为这些变更可能会导致短暂的末站服务缺失。由于其建立和维护的复杂性，不建议在链路上大量指定货运代理（超过65家）。
Disabling VLAN-x at an RBridge port cancels any Appointed Forwarder status that RBridge has for VLAN-x unless VLAN-x is enabled on some other port that the RBridge has connected to the same link. Configuring a port as a trunk port or point-to-point port revokes any Appointed Forwarder status that depends on enabled VLANs at that port.
在RBridge端口禁用VLAN-x将取消RBridge为VLAN-x指定的任何转发器状态，除非在RBridge已连接到同一链路的其他端口上启用VLAN-x。将端口配置为中继端口或点对点端口将取消任何指定的转发器状态，该状态取决于该端口上已启用的VLAN。
Causing a port to no longer be configured as a trunk or point-to-point port or enabling VLAN-x on a port does not, in itself, cause the RBridge to become an Appointed Forwarder for the link that port is on. However, such actions can allow the port's RBridge to become Appointed Forwarder by choice if it is the DRB or by appointment, if it is not the DRB on the link.
使端口不再配置为中继或点对点端口或在端口上启用VLAN-x本身不会导致RBridge成为该端口所在链路的指定转发器。然而，如果是DRB，则此类行动可允许港口的RBridge通过选择成为指定的货运代理，如果不是链路上的DRB，则通过指定成为指定的货运代理。
TRILL Hellos include a field that is set to the VLAN in which they are sent. If they arrive on a different VLAN, then VLAN mapping is occurring within the link. (Such VLAN mapping within a link between RBridges should not be confused with VLAN mapping inside an RBridge [VLANMAP]). VLAN mapping between VLAN-x and VLAN-y can lead to a loop if the Appointed Forwarders for the VLANs are different. If such mapping within a link was allowed and occurred on two or more links so that there was a cycle of VLAN mappings, a broadcast frame, for example, would loop forever.
TRILL Hello包括一个字段，该字段设置为发送它们的VLAN。如果它们到达不同的VLAN，那么VLAN映射将在链路中发生。（RBridge之间链路内的这种VLAN映射不应与RBridge[VLANMAP]内的VLAN映射混淆。）。如果为VLAN指定的转发器不同，VLAN-x和VLAN-y之间的VLAN映射可能导致循环。如果允许在一条链路中进行这种映射，并且这种映射发生在两条或多条链路上，因此存在一个VLAN映射周期，例如，广播帧将永远循环。
To prevent this potential problem, if the DRB on a link detects VLAN mapping by receiving a Hello in VLAN-x that was sent on VLAN-y, it MUST make or revoke appointments so as to assure that the same RBridge (possibly the DRB) is the Appointed Forwarder on the link for both VLAN-x and VLAN-y.
为防止此潜在问题，如果链路上的DRB通过接收VLAN-y上发送的VLAN-x中的Hello来检测VLAN映射，则必须进行或撤销预约，以确保相同的RBridge（可能是DRB）是VLAN-x和VLAN-y链路上的指定转发器。
An RBridge has, for every link on which it can offer end station service (that is every link for which it can act as an Appointed Forwarder), the following timers denominated in seconds:
RBridge对于其可提供端站服务的每条链路（即其可作为指定转发器的每条链路），都有以下以秒为单位的计时器：
- a DRB inhibition timer,
- DRB抑制定时器，
- a root change inhibition timer, and
- 根变化抑制计时器，以及
- up to 4,094 VLAN inhibition timers, one for each legal VLAN ID.
- 最多4094个VLAN抑制计时器，每个合法VLAN ID对应一个。
The DRB and root change inhibition timers MUST be implemented.
必须实现DRB和根更改抑制计时器。
The loss of native traffic due to inhibition will be minimized by logically implementing a VLAN inhibition timer per each VLAN for which end station service will ever be offered by the RBridge on the link; this SHOULD be done. (See the Appendix for an example motivating VLAN inhibition timers.) However, if implementation limitations make a full set of such timers impractical, the VLAN inhibition timers for more than one VLAN can, with care, be merged into one timer. In particular, an RBridge MUST NOT merge the VLAN inhibition timers together for two VLANs if it is the Appointer Forwarder for one and not for the other, as this can lead to unnecessary indefinitely prolonged inhibition. In the limit, there will be safe operations, albeit with more native frame loss than would otherwise be required, even if only two VLAN inhibition timers are provided: one for VLANs for which the RBridge is the Appointed Forwarder and one for all other VLANs. At least two VLAN inhibition
通过在逻辑上为每个VLAN实现VLAN抑制计时器，可以最大限度地减少由于抑制而导致的本机流量损失，RBridge将在链路上为每个VLAN提供终端站服务；应该这样做。（关于激励VLAN抑制计时器的示例，请参见附录。）但是，如果实施限制使得一整套此类计时器不可行，则可以小心地将多个VLAN的VLAN抑制计时器合并到一个计时器中。特别是，如果RBridge是一个VLAN而不是另一个VLAN的对应转发器，则RBridge不得将两个VLAN的VLAN抑制计时器合并在一起，因为这可能导致不必要的无限期延长抑制。在该限制下，将有安全操作，尽管本机帧丢失比其他情况下需要的更多，即使只提供两个VLAN抑制计时器：一个用于RBridge为其指定转发器的VLAN，另一个用于所有其他VLAN。至少两个VLAN抑制
timers MUST be implemented. Where a VLAN inhibition timer represents more than one VLAN, an update or test that would have been done to the timer for any of the VLANs is performed on the merged timer.
必须实施计时器。如果VLAN抑制计时器表示多个VLAN，则会在合并计时器上对任何VLAN的计时器执行更新或测试。
These timers are set as follows:
这些定时器设置如下：
1. On booting or management reset, each port will have its own set of timers, even if two or more such ports are on the same link, because the RBridge will not have had a chance to learn that yet. All inhibition timers are set to expired except the DRB inhibition timer that is set in accordance with item 2 below. The DRB inhibition timer is handled differently because each port will initially believe it is the DRB.
1. 在引导或管理重置时，每个端口都将有自己的一组计时器，即使两个或更多这样的端口位于同一链路上，因为RBridge还没有机会了解到这一点。除根据以下第2项设置的DRB抑制定时器外，所有抑制定时器均设置为过期。DRB抑制计时器的处理方式不同，因为每个端口最初都认为它是DRB。
2. When an RBridge decides that it has become the DRB on a link, including when it is first booted or reset by management, it sets the DRB inhibition timer to the Holding Time of its port on that link that won the DRB election.
2. 当RBridge决定它已成为链路上的DRB时，包括管理层首次启动或重置时，它会将DRB抑制计时器设置为该链路上赢得DRB选举的端口的保持时间。
3. When an RBridge decides that it has lost DRB status on a link, it sets the DRB inhibition timer to expired.
3. 当RBridge确定其已失去链路上的DRB状态时，它会将DRB抑制计时器设置为过期。
Note: In the rare corner case where one port of an RBridge was the DRB election winner, but later lost the DRB election to a different port of the same RBridge on that link (perhaps due to management configuration of port priority), neither 2 nor 3 above applies, and the DRB timer is not changed.
注意：在罕见的情况下，RBridge的一个端口是DRB选择的赢家，但后来在该链路上的同一RBridge的另一个端口上失去了DRB选择（可能是由于端口优先级的管理配置），上述2和3都不适用，并且DRB计时器没有更改。
4. When an RBridge RB1 receives a TRILL Hello asserting that the sender is the Appointed Forwarder that either (1) arrives on VLAN-x or (2) was sent on VLAN-x as indicated inside the Hello, then RB1 sets its VLAN-x inhibition timer for the link to the maximum of that timer's existing value and the Holding Time in the received Hello. An RBridge MUST maintain VLAN inhibition timers for a link to which it connects if it can offer end station service on that link even if it is not currently Appointed Forwarder for any VLAN on that link.
4. 当RBridge RB1接收到TRILL Hello，断言发送方是指定的转发器，即（1）到达VLAN-x或（2）在VLAN-x上发送，如Hello中所示，RB1将其链路的VLAN-x抑制计时器设置为该计时器的现有值和接收Hello中的保持时间的最大值。如果RBridge能够在该链路上提供终端站服务，则RBridge必须为其所连接的链路维护VLAN抑制计时器，即使它当前不是该链路上任何VLAN的指定转发器。
5. When an RBridge RB1 enables VLAN-x on a port connecting to a link and VLAN-x was previously not enabled on any of RB1's ports on that link, it sets its VLAN inhibition timer for VLAN-x for that link to its Holding Time for that port. This is done even if the port is configured as a trunk or point-to-point port as long as there is some chance it might later be configured not to be a trunk or point-to-point port.
5. 当RBridge RB1在连接到链路的端口上启用VLAN-x，并且以前未在该链路上的任何RB1端口上启用VLAN-x时，它会将该链路的VLAN-x的VLAN抑制计时器设置为该端口的保持时间。即使将端口配置为中继或点对点端口，只要以后可能会将其配置为非中继或点对点端口，也可以执行此操作。
6. When an RBridge detects a change in the common spanning tree root bridge on a port, it sets its root change inhibition timer for the link to an amount of time that defaults to 30 seconds and is configurable to any value from 30 down to zero seconds. This condition will not occur unless the RBridge is receiving Bridge PDU (BPDUs) on the port from an attached bridged LAN. It is safe to configure this inhibition time to the settling time of an attached bridged LAN. For example, if it is known that Rapid Spanning Tree Protocol (RSTP [802.1Q]) is running throughout the attached bridged LAN, it should be safe to configure this inhibition time to 7 seconds or, if the attached bridges have been configured to have a minimum Bridge Hello Timer, safe to configure it to 4 seconds. Note that, while an RBridge could determine what version of spanning tree is running on the physical link between it and any directly connected bridge by examination of the BPDUs it receives, it could not tell if inter-bridge links beyond those directly connected bridges were running classic Spanning Tree Protocol (STP), which might require the root change inhibition timer to be set to 30 seconds for safety.
6. 当RBridge检测到端口上的公共生成树根网桥发生更改时，它会将链路的根更改抑制计时器设置为默认为30秒的时间量，并可配置为从30秒到零秒的任何值。除非RBridge在端口上从连接的桥接LAN接收桥接PDU（BPDU），否则不会出现这种情况。将此抑制时间配置为连接的桥接LAN的稳定时间是安全的。例如，如果已知快速生成树协议（RSTP[802.1Q]）正在连接的桥接LAN中运行，则应安全地将该抑制时间配置为7秒，或者，如果连接的网桥已配置为具有最小网桥Hello定时器，则应安全地将其配置为4秒。注意，尽管RBridge可以通过检查它接收到的BPDU来确定它和任何直接连接的网桥之间的物理链路上运行的是什么版本的生成树，但它无法判断那些直接连接的网桥之外的网桥间链路是否运行经典生成树协议（STP），为了安全起见，可能需要将根更改抑制计时器设置为30秒。
7. When an RBridge decides that one of its ports (or a set of its ports) P1 is on the same link as another of its ports (or set of its ports) P2, then the inhibition timers are merged to a single set of inhibition timers by using the maximum value of the corresponding timers.
7. 当RBridge确定其一个端口（或其一组端口）P1与其另一个端口（或其一组端口）P2位于同一链路上时，则通过使用相应定时器的最大值将抑制定时器合并到单个抑制定时器组。
8. When an RBridge decides that a set of its ports that it had been treating as being on the same link are no longer on the same link, those ports will necessarily be on two or more links (one link per port in the limit). This is handled by cloning a copy of the timers for each of the two or more links to which the RBridge has decided these ports connect.
8. 当RBridge决定它一直视为在同一链路上的一组端口不再在同一链路上时，这些端口必须在两个或多个链路上（限制中每个端口一个链路）。这是通过为RBridge已确定这些端口连接的两个或多个链路中的每一个克隆计时器副本来实现的。
An Appointed Forwarder for a link is inhibited for VLAN-x if:
在以下情况下，VLAN-x将禁止指定的链路转发器：
1. its DRB inhibition timer for that link is not expired, or
1. 该链路的DRB抑制计时器未过期，或
2. its root change inhibition timer for that link is not expired, or
2. 该链接的根更改抑制计时器未过期，或
3. its VLAN inhibition timer for that link for VLAN-x is not expired.
3. VLAN-x链路的VLAN抑制计时器未过期。
If a VLAN-x Appointed Forwarder for a link is inhibited and receives a TRILL Data frame whose encapsulated frame is in VLAN-x and would normally be egressed to that link, it decapsulates the native frame
如果为链路指定的VLAN-x转发器被禁止，并接收到一个TRILL数据帧，该数据帧的封装帧位于VLAN-x中，并且通常会被导出到该链路，则该转发器将解除对本机帧的封装
as usual. However, it does not output it to or queue it for that link, although, if appropriate (for example, the frame is multi-destination), it may output it to or queue it for other links.
像往常一样。但是，它不会将其输出到该链路或为该链路对其进行排队，尽管在适当的情况下（例如，帧是多目的地），它可以将其输出到其他链路或为其他链路对其进行排队。
If a VLAN-x Appointed Forwarder for a link is inhibited and receives a native frame in VLAN-x that would normally be ingressed from that link, the native frame is ignored except for address learning.
如果为链路指定的VLAN-x转发器被禁止，并在VLAN-x中接收通常从该链路进入的本机帧，则本机帧将被忽略，但地址学习除外。
An RBridge with one or more unexpired inhibition timers, possibly including an unexpired inhibition timer for VLAN-x, is still required to indicate in TRILL Hellos it sends on VLAN-x whether or not it is Appointed Forwarder for VLAN-x for the port on which it sends the Hello.
带有一个或多个未过期禁止计时器（可能包括VLAN-x的未过期禁止计时器）的RBridge仍然需要在VLAN-x上发送的TRILL Hello中指示它是否为VLAN-x指定了发送Hello的端口的转发器。
Inhibition has no effect on the receipt or forwarding of TRILL Data frames.
抑制对TRILL数据帧的接收或转发没有影响。
An RBridge may have multiple ports on the same link. Some of these ports may be suspended due to MAC address duplication as described in [RFC6327]. Suspended ports never ingress or egress native frames.
RBridge在同一链路上可能有多个端口。如[RFC6327]所述，其中一些端口可能由于MAC地址重复而挂起。挂起的端口从不进出本机帧。
If an RBridge has one or more non-suspended ports on a link and those ports offer end station service, that is, those ports are not configured as point-to-point or trunk ports, then that RBridge is eligible to be an Appointed Forwarder for that link. It can become Appointed Forwarder either by its choice, because it is the DRB, or by appointment by the DRB as described in Sections 2.1 and 2.2.
如果RBridge在链路上有一个或多个非挂起端口，并且这些端口提供端站服务，即，这些端口未配置为点对点或中继端口，则RBridge有资格成为该链路的指定转发器。它可以通过自己的选择（因为它是DRB）或通过第2.1节和第2.2节所述的DRB的任命成为指定的货运代理。
If an RBridge that is the Appointed Forwarder for VLAN-x on a link has multiple non-suspended ports on that link, it may load share the task of ingressing and egressing VLAN-x native frames across those ports however it chooses, as long as there is no case in which a frame it egresses onto the link from one port can be ingressed on another of its ports, creating a loop. If the RBridge is the Appointed Forwarder for multiple VLANs, a straightforward thing to do would be to partition those VLANs among the ports it has on the link.
如果作为链路上VLAN-x的指定转发器的RBridge在该链路上具有多个非挂起端口，则它可能会在这些端口上以其选择的方式加载和共享VLAN-x本机帧的进出任务，只要不存在从一个端口进入链路的帧可以进入其另一个端口的情况，就可以创建循环。如果RBridge是多个VLAN的指定转发器，那么一件简单的事情就是将这些VLAN划分到它在链路上拥有的端口中。
This memo provides improved documentation of the TRILL Appointed Forwarder mechanism. It does not change the security considerations of the TRILL base protocol. See Section 6 of [RFC6325].
本备忘录提供了TRILL指定货运代理机制的改进文档。它不会改变TRILL基本协议的安全考虑。见[RFC6325]第6节。
The authors of [RFC6325] and [RFC6327], those listed in the Acknowledgements section of [RFC6325] and [RFC6327], and Ron Bonica, Stewart Bryant, Linda Dunbar, Les Ginsberg, Erik Nordmark, Dan Romascanu, and Mike Shand are hereby thanked for their contributions.
在此感谢[RFC6325]和[RFC6327]的作者，[RFC6325]和[RFC6327]的致谢部分中列出的作者，以及罗恩·博尼卡、斯图尔特·布莱恩特、琳达·邓巴、莱斯·金斯伯格、埃里克·诺德马克、丹·罗马斯坎努和迈克·山德的贡献。
Normative and Informative references for this document are listed below.
本文件的规范性和信息性参考文件如下所示。
[802.1Q] IEEE 802.1, "IEEE Standard for Local and metropolitan area networks - Virtual Bridged Local Area Networks", IEEE Std 802.1Q-2011, May 2011.
[802.1Q]IEEE 802.1，“局域网和城域网的IEEE标准-虚拟桥接局域网”，IEEE标准802.1Q-2011，2011年5月。
[IS-IS] ISO/IEC 10589:2002, Second Edition, "Intermediate System to Intermediate System Intra-Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", 2002.
[IS-IS]ISO/IEC 10589:2002，第二版，“与提供无连接模式网络服务的协议一起使用的中间系统到中间系统域内路由交换协议（ISO 8473）”，2002年。
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual environments", RFC 1195, December 1990.
[RFC1195]Callon，R.，“OSI IS-IS在TCP/IP和双环境中的路由使用”，RFC 11951990年12月。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A. Ghanwani, "Routing Bridges (RBridges): Base Protocol Specification", RFC 6325, July 2011.
[RFC6325]帕尔曼，R.，伊斯特莱克第三，D.，杜特，D.，盖伊，S.，和A.加瓦尼，“路由桥（RBridges）：基本协议规范”，RFC6325，2011年7月。
[RFC6326] Eastlake, D., Banerjee, A., Dutt, D., Perlman, R., and A. Ghanwani, "Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS", RFC 6326, July 2011.
[RFC6326]伊斯特莱克，班纳吉，A.，杜特，D.，帕尔曼，R.，和A.加瓦尼，“IS-IS大量链路的透明互连（TRILL）使用”，RFC 63262011年7月。
[RFC6327] Eastlake 3rd, D., Perlman, R., Ghanwani, A., Dutt, D., and V. Manral, "Routing Bridges (RBridges): Adjacency", RFC 6327, July 2011.
[RFC6327]东湖第三大道、佩尔曼大道、加瓦尼大道、杜特大道和V.曼拉尔大道，“路由桥（RBridges）：邻近”，RFC 6327，2011年7月。
[VLANMAP] Perlman, R., Dutt, D., Banerjee, A., Rijhsinghani, A., and D. Eastlake, "RBridges: Campus VLAN and Priority Regions", Work in Progress, October 2011.
[VLANMAP]Perlman，R.，Dutt，D.，Banerjee，A.，Rijhsinghani，A.，和D.Eastlake，“RBridges:校园VLAN和优先区域”，正在进行的工作，2011年10月。
Appendix. VLAN Inhibition Example
附录VLAN抑制示例
The per-VLAN inhibition timers (or the equivalent) are needed to be loop safe in the case of misconfigured bridges on a link.
当链路上的网桥配置错误时，每VLAN抑制定时器（或等效定时器）需要是环路安全的。
For a simple example, assume that RB1 and RB2 are the only RBridges on the link, that RB1 is higher priority to be the DRB, and that they both want VLAN 1 (the default) to be the Designated VLAN. However, there is a bridge between them configured so that RB1 can see all the frames sent by RB2 but none of the frames from RB1 can get through to RB2.
对于一个简单的示例，假设RB1和RB2是链路上唯一的RBridge，RB1作为DRB具有更高的优先级，并且它们都希望VLAN 1（默认值）作为指定的VLAN。但是，它们之间有一个桥接器，配置为RB1可以看到RB2发送的所有帧，但RB1的所有帧都无法通过RB2。
Both will think they are the DRB. RB1 because it is higher priority even though it sees the Hellos from RB2, and RB2 because it doesn't see the Hellos from RB1 and therefore thinks it is highest priority.
两人都会认为他们是DRB。RB1是因为它的优先级更高，即使它从RB2看到了hello，而RB2是因为它没有从RB1看到hello，因此认为它是最高优先级。
Say RB1 chooses to act as Appointed Forwarder for VLANs 2 and 3 while RB2 chooses to act as Appointed Forwarder for VLANs 3 and 4. There is no problem with VLANs 2 and 4 but if you do not do something about it, you could have a loop involving VLAN 3. RB1 will see the Hellos RB2 issues on VLAN 3 declaring itself Appointed Forwarder, so RB1 will be inhibited on VLAN 3. RB2 does not see the Hellos issued by RB1 on VLAN 3, so RB2 will become uninhibited and will handle VLAN 3 native traffic.
假设RB1选择作为VLAN 2和3的指定转发器，而RB2选择作为VLAN 3和4的指定转发器。VLAN2和VLAN4没有问题，但如果您不采取措施，可能会有一个涉及VLAN3的循环。RB1将在VLAN 3上看到Hellos RB2问题，声明自己为指定转发器，因此在VLAN 3上RB1将被禁止。RB2看不到RB1在VLAN 3上发出的Hello，因此RB2将变得不受限制，并将处理VLAN 3本机流量。
However, this situation may change. RB2 might crash, the bridge might crash, or RB2 might be reconfigured so it no longer tried to act as Appointed Forwarder for VLAN 3, or other issues may occur. So, RB1 has to maintain a VLAN 3 inhibition timer, and if it sees no Hellos from any other RBridge on the link claiming to be Appointed Forwarder for VLAN 3 in a long enough time, then RB1 becomes uninhibited for that VLAN on the port in question and can handle end station traffic in VLAN 3.
然而，这种情况可能会改变。RB2可能会崩溃，网桥可能会崩溃，或者RB2可能会重新配置，以便不再尝试充当VLAN 3的指定转发器，或者可能会发生其他问题。因此，RB1必须维护一个VLAN 3抑制计时器，如果在足够长的时间内，它在链路上没有看到任何其他RBridge声称是VLAN 3的指定转发器，则RB1对所述端口上的该VLAN不受限制，并且可以处理VLAN 3中的端站流量。
Authors' Addresses
作者地址
Radia Perlman Intel Labs 2200 Mission College Blvd. Santa Clara, CA 95054 USA
Radia Perlman英特尔实验室使命学院大道2200号。美国加利福尼亚州圣克拉拉95054
Phone: +1-408-765-8080
EMail: Radia@alum.mit.edu
Phone: +1-408-765-8080
EMail: Radia@alum.mit.edu
Donald Eastlake 3rd Huawei Technologies 155 Beaver Street Milford, MA 01757 USA
美国马萨诸塞州米尔福德市比弗街155号唐纳德东湖第三华为技术有限公司01757
Phone: +1-508-333-2270
EMail: d3e3e3@gmail.com
Phone: +1-508-333-2270
EMail: d3e3e3@gmail.com
Yizhou Li Huawei Technologies 101 Software Avenue, Nanjing 210012, China
中国南京软件大道101号宜州利华为技术有限公司，邮编：210012
Phone: +86-25-56622310
EMail: liyizhou@huawei.com
Phone: +86-25-56622310
EMail: liyizhou@huawei.com
Ayan Banerjee Cisco Systems 170 West Tasman Drive San Jose, CA 95134 USA
美国加利福尼亚州圣何塞西塔斯曼大道170号Ayan Banerjee Cisco Systems，邮编95134
Phone: +1-408-333-7149
EMail: ayabaner@cisco.com
Phone: +1-408-333-7149
EMail: ayabaner@cisco.com
Fangwei Hu ZTE Corporation 889 Bibo Road Shanghai 201203 China
中国上海碧波路889号方伟胡中兴通讯股份有限公司201203
Phone: +86-21-68896273
EMail: hu.fangwei@zte.com.cn
Phone: +86-21-68896273
EMail: hu.fangwei@zte.com.cn