不涉及
某局点ADCOMPUS5.0方案和传统网共有核心交换机,现场反馈传统网终端通过IPv6访问外网网址时,出现卡顿现象,通过PC直连设备来排查沿途故障设备,发现只有当PC接到核心交换机,才会出现卡顿现象,故怀疑交换机出现问题。
首先在故障现象时,在核心交换机上下行口做双向流统,确定交换机是否丢包,结果显示,TCP报文上行没有问题,下行时有进无处,确定交换机有故障。并重点排查交换机上回程路由信息。
Interface: Ten-GigabitEthernet1/3/0/37------下行
Direction: Inbound
Policy: lt
Classifier: lt
Operator: AND
Rule(s) :
If-match acl ipv6 3333
Behavior: lt
Accounting enable:
2323 (Packets)
0 (pps)
Interface: Ten-GigabitEthernet1/3/0/37
Direction: Outbound
Policy: lt
Classifier: lt
Operator: AND
Rule(s) :
If-match acl ipv6 3333
Behavior: lt
Accounting enable:
0 (Packets)
0 (pps)
Interface: Ten-GigabitEthernet1/3/0/44-----上行
Direction: Inbound
Policy: lt
Classifier: lt
Operator: AND
Rule(s) :
If-match acl ipv6 3333
Behavior: lt
Accounting enable:
3308 (Packets)
0 (pps)
Interface: Ten-GigabitEthernet1/3/0/44
Direction: Outbound
Policy: lt
Classifier: lt
Operator: AND
Rule(s) :
If-match acl ipv6 3333
Behavior: lt
Accounting enable:
2323 (Packets)
0 (pps)
然后在交换机上查看设备到终端的回程路由发现,在外网出口vpn,即vpna 的路由表中只有对应终端的64位网段路由而无128位主机路由,该网段路由通过路由复制功能从中间vpnb复制过来,而vpnb和vpn-default则通过RT值互引实现路由学习,查看vpn-default路由表中也只有64位网段路由,在交换机上查看ND表项发现是有对应表项的。
Summary count : 1
Destination: 2001:250:5839:600::/64 Protocol : BGP4+
NextHop : :: Preference: 130
Interface : Vlan1 Cost: 0
[S12508G-AF]display ipv6 routing-table vpn-instance vpnb 2001:250:5839:600::8
Summary count : 2
Destination: ::/0 Protocol : Static
NextHop : 2001:250:5839:FF01:10:10:4:13 Preference: 60
Interface : Vlan4050 Cost : 0
Destination: 2001:250:5839:600::/64 Protocol : BGP4+
NextHop : :: Preference: 130
Interface : Vlan1 Cost : 0
[S12508G-AF]display ipv6 routing-table vpn-instance vpn-default
2001:250:5839:600::8
Summary count : 2
Destination: ::/0 Protocol : BGP4+
NextHop : 2001:250:5839:FF01:10:10:4:13 Preference: 130
Interface : Vlan4050 Cost: 0
Destination: 2001:250:5839:600::/64 Protocol : Direct
NextHop : :: Preference: 0
Interface : Vlan1 Cost: 0
[S12508G-AF]disp"la"y ipv6 neighbors 2001:250:5839:600::8
Type: S-Static D-Dynamic O-Openflow R-Rule IS-Invalid static
IPv6 address MAC address VLAN/VSI Interface State T Aging
2001:250:5839:600::8 0023-24a3-41da 1 XGE1/3/0/37 REACH D 655
通过查询平台路由表项,并结合查询路由的硬件表项,发现按照网段路由表项转发报文会上送平台进行软转,则当访问外网地址时,报文量较大就会导致卡顿。在IPV4网络中,配置vpna从vpnb中route-replicate 复制路由,当交换机收到去往终端的报文后,通过复制的路由上送平台,触发ARP学习,最后在vpna中有到终端的32位主机路由。在IPV6网络,配置route-replicate复制路由后,交换机收到IPV6报文后,通过复制的路由上送平台后,不会触发ND学习,从而在vpna中没有到终端的128位主机路由。
[S12508G-AF-probe]debug ipv6-drv show route 3 2001:250:5839:600::8 ch 1 sl 3
**********************************************************
- IPv6 Route Information Chassis 1 Slot 3
**********************************************************
--- UNIT: 0 ---
- IPv6 ADDR: 2001:0250:5839:0600:0000:0000:0000:0008
- VRF: 3
- MASKLEN: 64
- EGRESS ID: 149153 ------上送平台
- FLAGS: 0x2000c
- PRI: 0
- CLASS ID: 2
- HWINDEX: 259
- TUNNEL OPT: 0
- HITBIT: Source Dest
在终端所在vlan对应的vlan虚接口下配置ipv6 nd route-direct advertise命令用来开启ND直连路由通告功能, 设备通过该接口学习到的ND表项生成128位的主机路由,vpn-default通过引入直连路由引入该主机路由,继而再通过路由互引和route-replicate复制到vpna中,在vpna中就有到终端的128位路由,此时交换机才能硬转,故障恢复。
[S12508G-AF]display ipv6 routing-table vpn-instance vpna 2001:250:5839:600::8
Summary count : 2
Destination: 2001:250:5839:600::/64
Protocol : BGP4+
NextHop : :: Preference: 130
Interface : Vlan1 Cost : 0
Destination: 2001:250:5839:600::8/128 Protocol
: BGP4+
NextHop :
2001:250:5839:600::8 Preference:
130
Interface : Vlan1 Cost : 0
[S12508G-AF] display ipv6 routing-table vpn-instance vpnb 2001:250:5839:600::8 128
Summary count : 1
Destination: 2001:250:5839:600::8/128 Protocol : BGP4+
NextHop : 2001:250:5839:600::8 Preference: 130
Interface : Vlan1 Cost : 0
[S12508G-AF] display ipv6 routing-table vpn-instance vpn-default 2001:250:5839:600::8 128
Summary count : 1
Destination: 2001:250:5839:600::8/128
Protocol : Direct
NextHop :
2001:250:5839:600::8 Preference:
0
Interface : Vlan1 Cost : 0