MPLS 初学者的常见问题

深藏阁楼爱情的钟 2022-01-29 11:27 252阅读 0赞

**中文: **

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## 问题 ##

> **[前言][Link 1]   
> [什么是多协议标签交换 (MPLS)？][_MPLS]   
> [什么是标签？ 标签的结构是什么？][Link 2]   
> [标签将附加到数据包中的什么位置？][Link 3]   
> [什么是转发等效类 (FEC)？][_FEC]   
> [什么是上游标签交换路由器 (LSR)？ 什么是下游 LSR？][_LSR_ _ LSR]   
> [对于 10.1.1.0/24，R3 是 R4 的“下游”LSR 吗？][10.1.1.0_24_R3 _ R4 _LSR]   
> [提到标签时，术语传入、传出、本地和远程的含义是什么？][Link 4]   
> [LSR 能在 MPLS 接口上传输/接收本地 IP 数据包（非 MPLS）吗？][LSR _ MPLS _ IP _ MPLS]   
> [LSR 能在非 MPLS 接口上接收/传输带有标记的数据包吗？][LSR _ MPLS]   
> [哪些平台和 Cisco IOS 支持 MPLS？][Cisco IOS _ MPLS]   
> [通用路由封装 (GRE) 隧道的开销是 24 个字节。 那么，一个 MPLS LSP 隧道的开销是多少？][_GRE_ _ 24 _ _ MPLS LSP]   
> [LSR 如何判断哪个是标签堆栈的顶部标签、底部标签和中间标签？][LSR]   
> [标签值的范围是多少？ 保留了哪些标签值？ 这些保留值的含义是什么？][Link 5]   
> [LDP 和 TDP 使用哪些协议和端口号向 LDP/TDP 对等体分配标签？][LDP _ TDP _ LDP_TDP]   
> [Catalyst 6500 和 7600 光纤业务路由器 (OSR) 对 MPLS 的支持存在哪些限制？][Catalyst 6500 _ 7600 _ _OSR_ _ MPLS]   
> [在哪里能找到 MPLS 配置示例？][MPLS]   
> [哪些选项可用于负载均衡 MPLS 数据包？][MPLS 1]   
> [能否通过 MPLS 连接配置不同站点上两台 Cisco Catalyst 交换机之间的 802.1Q trunk？][MPLS _ Cisco Catalyst _ 802.1Q trunk]   
> [流出的MPLS EXP值是否继承在流入的IP数据包的DSCP值默认情况下或流入DSCP委托是否是没有在MPLS的任何更多的配置启用接口？][MPLS EXP_IP_DSCP_DSCP_MPLS]   
> [DHCP中继功能是否工作在MPLS VPN网络？][DHCP_MPLS VPN]**

**   更多参见: [http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners\_chs.html][http_www.china-ccie.com_doc_MPLS-FAQ-For-Beginners_MPLS-FAQ-For-Beginners_chs.html]**

**英文: **

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## Questions ##

**[Introduction][]   
[What is Multi-Protocol Label Switching (MPLS)? ][What is Multi-Protocol Label Switching _MPLS]  
[What is a label? What is the structure of the label? ][What is a label_ What is the structure of the label]  
[Where will the label be imposed in a packet? ][Where will the label be imposed in a packet]  
[What is a Forwarding Equivalence Class (FEC)? ][What is a Forwarding Equivalence Class _FEC]  
[What is an upstream label switch router (LSR)? What is a downstream LSR? ][What is an upstream label switch router _LSR_ What is a downstream LSR]  
[Is R3 a "Downstream" LSR to R4 for 10.1.1.0/24? ][Is R3 a _Downstream_ LSR to R4 for 10.1.1.0_24]  
[What do the terms incoming, outgoing, local, and remote mean when referring to labels? ][What do the terms incoming_ outgoing_ local_ and remote mean when referring to labels]  
[Can an LSR transmit/receive a native IP packet (non-MPLS) on an MPLS interface? ][Can an LSR transmit_receive a native IP packet _non-MPLS_ on an MPLS interface]  
[Can an LSR receive/transmit a labeled packet on a non-MPLS interface? ][Can an LSR receive_transmit a labeled packet on a non-MPLS interface]  
[What platforms and Cisco IOSes support MPLS? ][What platforms and Cisco IOSes support MPLS]  
[Generic Routing Encapsulation (GRE) tunnel has an overhead of 24 bytes. How much overhead does an MPLS LSP tunnel have? ][Generic Routing Encapsulation _GRE_ tunnel has an overhead of 24 bytes. How much overhead does an MPLS LSP tunnel have]  
[How does the LSR know which is the top label, bottom label, and a middle label of the label stack? ][How does the LSR know which is the top label_ bottom label_ and a middle label of the label stack]  
[What is the range of label values? What label values are reserved? What do the reserved values signify? ][What is the range of label values_ What label values are reserved_ What do the reserved values signify]  
[What protocol and port numbers do LDP and TDP use to distribute labels to LDP/TDP peers? ][What protocol and port numbers do LDP and TDP use to distribute labels to LDP_TDP peers]  
[What restrictions exist for MPLS support on the Catalyst 6500 and 7600 Optical Services Router (OSR)? ][What restrictions exist for MPLS support on the Catalyst 6500 and 7600 Optical Services Router _OSR]  
[Where can I find MPLS configuration samples? ][Where can I find MPLS configuration samples]  
[What options are available for load balancing MPLS packets?][What options are available for load balancing MPLS packets]   
[Can we configure an 802.1Q trunk between two Cisco Catalyst switches on different sites over a MPLS connection?][Can we configure an 802.1Q trunk between two Cisco Catalyst switches on different sites over a MPLS connection]   
[Does the outgoing MPLS EXP value inherit the DSCP value in incoming IP packets by default or is the incoming DSCP trusted without any additional configuration on an MPLS enabled interface?][Does the outgoing MPLS EXP value inherit the DSCP value in incoming IP packets by default or is the incoming DSCP trusted without any additional configuration on an MPLS enabled interface]   
[Does DHCP relay function work in the MPLS VPN network?][Does DHCP relay function work in the MPLS VPN network]**

** 更多参看: [http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners\_eng.html][http_www.china-ccie.com_doc_MPLS-FAQ-For-Beginners_MPLS-FAQ-For-Beginners_eng.html]**

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[Link 1]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#intro
[_MPLS]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa1
[Link 2]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa2
[Link 3]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa3
[_FEC]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa4
[_LSR_ _ LSR]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa5
[10.1.1.0_24_R3 _ R4 _LSR]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa6
[Link 4]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa7
[LSR _ MPLS _ IP _ MPLS]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa8
[LSR _ MPLS]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa9
[Cisco IOS _ MPLS]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa10
[_GRE_ _ 24 _ _ MPLS LSP]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa11
[LSR]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#qa12
[Link 5]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#q13
[LDP _ TDP _ LDP_TDP]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#q14
[Catalyst 6500 _ 7600 _ _OSR_ _ MPLS]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#q15
[MPLS]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#q16
[MPLS 1]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#q17
[MPLS _ Cisco Catalyst _ 802.1Q trunk]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#q18
[MPLS EXP_IP_DSCP_DSCP_MPLS]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#q19
[DHCP_MPLS VPN]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html#q20
[http_www.china-ccie.com_doc_MPLS-FAQ-For-Beginners_MPLS-FAQ-For-Beginners_chs.html]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_chs.html
[Introduction]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#intro
[What is Multi-Protocol Label Switching _MPLS]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa1
[What is a label_ What is the structure of the label]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa2
[Where will the label be imposed in a packet]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa3
[What is a Forwarding Equivalence Class _FEC]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa4
[What is an upstream label switch router _LSR_ What is a downstream LSR]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa5
[Is R3 a _Downstream_ LSR to R4 for 10.1.1.0_24]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa6
[What do the terms incoming_ outgoing_ local_ and remote mean when referring to labels]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa7
[Can an LSR transmit_receive a native IP packet _non-MPLS_ on an MPLS interface]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa8
[Can an LSR receive_transmit a labeled packet on a non-MPLS interface]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa9
[What platforms and Cisco IOSes support MPLS]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa10
[Generic Routing Encapsulation _GRE_ tunnel has an overhead of 24 bytes. How much overhead does an MPLS LSP tunnel have]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa11
[How does the LSR know which is the top label_ bottom label_ and a middle label of the label stack]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#qa12
[What is the range of label values_ What label values are reserved_ What do the reserved values signify]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#q13
[What protocol and port numbers do LDP and TDP use to distribute labels to LDP_TDP peers]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#q14
[What restrictions exist for MPLS support on the Catalyst 6500 and 7600 Optical Services Router _OSR]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#q15
[Where can I find MPLS configuration samples]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#q16
[What options are available for load balancing MPLS packets]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#q17
[Can we configure an 802.1Q trunk between two Cisco Catalyst switches on different sites over a MPLS connection]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#q18
[Does the outgoing MPLS EXP value inherit the DSCP value in incoming IP packets by default or is the incoming DSCP trusted without any additional configuration on an MPLS enabled interface]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#q19
[Does DHCP relay function work in the MPLS VPN network]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html#q20
[http_www.china-ccie.com_doc_MPLS-FAQ-For-Beginners_MPLS-FAQ-For-Beginners_eng.html]: http://www.china-ccie.com/doc/MPLS-FAQ-For-Beginners/MPLS-FAQ-For-Beginners_eng.html