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标签为 ‘l2vpn’的文章

How to sniffer Dummy VLAN on L2VPN ?

什么是dummy vlan?

由于EVC平台在入端口可以通过rewrite命令剥离VLAN tag,这样导致在PW中没有任何tag,在Type 4时会有问题,两边VLAN的QOS无法传递给对端,所以就有了这个所谓的dummy vlan,它不是一个真正的VLAN,他只是传递一些QOS字段并且占一个位。那么dummy VLAN长什么样?其实大鹏之前的文章里已经详细介绍了EVC的各种行为,我这里只是介绍抓dummy VLAN的“心路历程”以及dummy VLAN的“样子”~

测试Topology:

起始测试环境为VPLS BGP auto discovery + LDP Sig,在76的入向抓包
dummy-vlan-topology

测试步骤

1. 默认Type 5,在CE1 ping 带cos 5,ASR9k-1在AC上不配置rewrite,透传的VLAN是否带着802.1p?根据抓包信息,正常带着802.1p,详细看“bgp-ldp-vlan-cos5.pcapng”;另外有个疑问,既然type 5支持VLAN透传,为什么还要Type 4?答案请看文章结束部分
完整阅读

ASR9k, GSR VPLS *PVID_Inc issue

跟同事讨论了下关于*PVID_Inc的问题,收益颇丰!估计没几个人能悟出在VPLS中PVID_inc的真谛。
为了验证讨论的内容,特意做下面的实验:

Topology

vpls-pvid-01
天蓝色属于一个bridge-domain vplstest1000;而红色属于bridge-domain vplstest6002
本文只讨论天蓝色的bridge-domain!

测试目的

验证下为什么会有PVID_inc的问题出现,及抓包分析,用有力的证据来验证
完整阅读

ASR9k Mapping Behavior for “translate 1-to-1 dot1q”

Topology

vpls-pvid-01
天蓝色属于一个bridge-domain vplstest1000;而红色属于bridge-domain vplstest6002
本文只讨论红色的bridge-domain!

测试目的

验证下ASR9k上的mapping行为 “translate 1-to-1 dot1q”
完整阅读

ASR9k Split-horizon Summary

对于ASR9k的split-horizon简单总结如下:

注:ASR9k不同于76,split-horizon不能disable;它一共分3组,group 0,1和2,每组的定义不一样。

  • 默认所有AC都属于group 0,group 0比较特殊,其中的AC都可以互访
  • 所有PW都属于group 1,group 1中的member不能互访,但能与group0或group 2互访
  • 不论在AC还是PW上配置split-horizion后,都会属于group 2,group2中的member不能互访,但能与group0或group1互访

下面是Xander总结的(https://supportforums.cisco.com/thread/2213114 ):

Three SHG groups are defined for VPLS(SHG0,SHG1 and SHG2). By default, all the 
bridge-ports( AC or PW ) come in SHG0. When a Split horizon-group is configured 
under the Bridge-port( either under AC or PW) they come in SHG2. 
PWs defined under VFI come in SHG1. 
By definition, Bridge-ports in same SHG(SHG1 and SHG2) won't talk to each 
other ( this is not applicable for SHG0 though ).

SHG0 --- > SHG0,SHG1 and SHG2
SHG1 --- > SHG0 and SHG2
SHG2 ----> SHG0 and SHG1

PW load share issue on ASR9k

There have 2 path between PE. And customer found 1st path have 5G traffics, 2nd path only have 300M traffics. After checked, customer have Eompls business.

And amount of traffics belong to l2VPN. In general, Loadbalancing in an MPLS network on Cisco routers is typically based upon the data that follows the bottom MPLS label. Refer to All traffic from one PW follows the same path, so have this issue.

Workaround:
We can use Flow Aware Transport (FAT) PW feature (from 4.2.1).
http://www.cisco.com/en/US/partner/docs/routers/asr9000/software/asr9k_r5.1/lxvpn/command/reference/b_vpn_cr51xasr9k_chapter_011.html#wp3812296210
完整阅读