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

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

Topology:
(access 1148)(non-ESport)ME3750(ESport)—–PW—–A9K(dot1q.1148)

3750 Config:

interface Vlan1148
no ip address
xconnect 2.2.2.2 23 encapsulation mpls pw-class cisco

pseudowire-class cisco
encapsulation mpls
interworking vlan

interface GigabitEthernet1/0/2
switchport access vlan 1148
switchport mode access
spanning-tree portfast

完整阅读