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本文档介绍set tloc-list操作的不适当的策略应用,当首选链路断开但备用路径仍然可用的某些情况下,该操作会导致流量黑洞。
注意:本文档中显示的所有命令输出均来自vEdge路由器。但是,对于运行IOS®-XE SDWAN软件的路由器,故障排除方法仍然相同。使用sdwan关键字在IOS®-XE SDWAN软件上获取相同的输出。例如,show sdwan omp routes而不是show omp routes。
为了便于演示和更好地理解后面描述的问题,请考虑以下拓扑图:
此外,下表汇总了系统设置:
主机名 | 站点ID | system-ip |
vedge1 | 13 个 | 10.155.0.118 |
vedge3 | 13 个 | 10.155.0.120 |
vedge4 | 4 | 10.155.0.50 |
vsmart1 | 1 | 10.155.0.3 |
vEdge1和vEdge3都配置了指向服务端VPN中某个下一跳的静态路由:
vpn 40 ip route 10.223.115.101/32 192.168.40.10 !
为了实现这些目标:
1.使vEdge1城域以太网链路成为进入“站点13”的入口流量的首选链路。
2. M将vEdge3城域以太网链路作为进入“站点13”的入口流量的第二个首选链路。
3.将vEdge1公共Internet链路作为进入“站点13”的入口流量的第三个首选链路。
4.使vEdge3公共 — internet链路成为进入“站点13”的入口流量的最低首选链路。
此vSmart控制策略配置如下:
policy lists tloc-list SITE13_TLOC_PREF tloc 10.155.0.118 color metro-ethernet encap ipsec preference 200 tloc 10.155.0.118 color public-internet encap ipsec preference 100 tloc 10.155.0.120 color metro-ethernet encap ipsec preference 150 tloc 10.155.0.120 color public-internet encap ipsec preference 50 ! prefix-list SITE13_PREFIX ip-prefix 10.223.115.101/32 ! site-list site13 site-id 13 ! control-policy TE_POLICY_2_SITE4 sequence 10 match route prefix-list SITE13_PREFIX ! action accept set tloc-list SITE13_TLOC_PREF ! ! ! default-action accept ! ! apply-policy site-list site4 control-policy TE_POLICY_2_SITE4 out ! !
vSmart通过4个可能的TLOC作为下一跳获取这些路由:
vsmart1# show omp routes 10.223.115.101/32 | b PATH PATH ATTRIBUTE VPN PREFIX FROM PEER ID LABEL STATUS TYPE TLOC IP COLOR ENCAP PREFERENCE -------------------------------------------------------------------------------------------------------------------------------------- 40 10.223.115.101/32 10.155.0.118 35 1002 C,R installed 10.155.0.118 metro-ethernet ipsec - 10.155.0.118 37 1002 C,R installed 10.155.0.118 public-internet ipsec - 10.155.0.120 35 1002 C,R installed 10.155.0.120 metro-ethernet ipsec - 10.155.0.120 37 1002 C,R installed 10.155.0.120 public-internet ipsec -
并相应地设置通告路由的优先级:
vsmart1# show omp routes 10.223.115.101/32 detail | nomore | b ADVERTISED | b "peer 10.155.0.50" | i Attributes\|originator\|\ tloc\|preference Attributes: originator 10.155.0.118 tloc 10.155.0.120, public-internet, ipsec preference 50 Attributes: originator 10.155.0.118 tloc 10.155.0.120, metro-ethernet, ipsec preference 150 Attributes: originator 10.155.0.118 tloc 10.155.0.118, public-internet, ipsec preference 100 Attributes: originator 10.155.0.118 tloc 10.155.0.118, metro-ethernet, ipsec preference 200
vEdge4选择适当的TLOC并将此路由安装到路由表中:
vedge4# show ip routes 10.223.115.101/32 | b PROTOCOL PROTOCOL NEXTHOP NEXTHOP NEXTHOP VPN PREFIX PROTOCOL SUB TYPE IF NAME ADDR VPN TLOC IP COLOR ENCAP STATUS --------------------------------------------------------------------------------------------------------------------------------------------- 40 10.223.115.101/32 omp - - - - 10.155.0.118 metro-ethernet ipsec F,S
流量转发按预期工作:
vedge4# traceroute vpn 40 10.223.115.101 Traceroute 10.223.115.101 in VPN 40 traceroute to 10.223.115.101 (10.223.115.101), 30 hops max, 60 byte packets 1 192.168.40.4 (192.168.40.4) 0.835 ms 0.984 ms 1.097 ms 2 192.168.40.10 (192.168.40.10) 2.955 ms 3.056 ms 3.218 ms
最终,vEdge1上发生故障,面向服务端LAN的接口关闭(或者管理员关闭以进行测试,例如,结果将相同):
vedge1# show interface vpn 40 IF IF IF TCP AF ADMIN OPER TRACKER ENCAP PORT SPEED MSS RX TX VPN INTERFACE TYPE IP ADDRESS STATUS STATUS STATUS TYPE TYPE MTU HWADDR MBPS DUPLEX ADJUST UPTIME PACKETS PACKETS ---------------------------------------------------------------------------------------------------------------------------------------------------------- 40 ge0/4 ipv4 192.168.40.4/24 Up Down NA null service 1500 00:50:56:be:91:36 - - 1420 - 129768 0
由于vEdge1没有10.223.115.101/32路由的有效下一跳,因此该路由会从路由和转发表中删除,并且不再将其通告给vSmart:
vedge1# show ip routes 10.223.115.101/32 | b PROTO PROTOCOL NEXTHOP NEXTHOP NEXTHOP VPN PREFIX PROTOCOL SUB TYPE IF NAME ADDR VPN TLOC IP COLOR ENCAP STATUS --------------------------------------------------------------------------------------------------------------------------------------------- 40 10.223.115.101/32 static - - 192.168.40.21 - - - - I vedge1# show ip fib vpn 40 | i 10.223.115.101/32 vedge1# vedge1# show omp routes 10.223.115.101/32 detail | nomore | b ADVERTISED vedge1#
同时,vEdge3仍会通告此路由(这是预期结果):
vedge3# show omp routes 10.223.115.101/32 detail | nomore | b ADVERTISED ADVERTISED TO: peer 10.155.0.3 Attributes: originator 10.155.0.120 label 1002 path-id 35 tloc 10.155.0.120, metro-ethernet, ipsec ultimate-tloc not set domain-id not set site-id 13 overlay-id 1 preference not set tag not set origin-proto static origin-metric 0 as-path not set unknown-attr-len not set Attributes: originator 10.155.0.120 label 1002 path-id 37 tloc 10.155.0.120, public-internet, ipsec ultimate-tloc not set domain-id not set site-id 13 overlay-id 1 preference not set tag not set origin-proto static origin-metric 0 as-path not set unknown-attr-len not set
vSmart现在可按预期从vEdge3获取2条路由:
vsmart1# show omp routes 10.223.115.101/32 | b PATH PATH ATTRIBUTE VPN PREFIX FROM PEER ID LABEL STATUS TYPE TLOC IP COLOR ENCAP PREFERENCE -------------------------------------------------------------------------------------------------------------------------------------- 40 10.223.115.101/32 10.155.0.120 35 1002 C,R installed 10.155.0.120 metro-ethernet ipsec - 10.155.0.120 37 1002 C,R installed 10.155.0.120 public-internet ipsec -
但与此同时,vSmart继续宣传以下内容:
vsmart1# show omp routes 10.223.115.101/32 detail | nomore | b ADVERTISED | b "peer 10.155.0.50" | i Attributes\|originator\|\ tloc\|preference Attributes: originator 10.155.0.120 tloc 10.155.0.120, public-internet, ipsec preference 50 Attributes: originator 10.155.0.120 tloc 10.155.0.120, metro-ethernet, ipsec preference 150 Attributes: originator 10.155.0.120 tloc 10.155.0.118, public-internet, ipsec preference 100 Attributes: originator 10.155.0.120 tloc 10.155.0.118, metro-ethernet, ipsec preference 200
如您所见,唯一的发起方已更改,这是预期行为,因为tloc-list操作与(大致来说)设置下一跳”操作类似,并且强制设置错误的TLOC,因此可达性丢失。
vedge4# ping vpn 40 10.223.115.101 count 5 Ping in VPN 40 PING 10.223.115.101 (10.223.115.101) 56(84) bytes of data. ^C --- 10.223.115.101 ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 3999ms vedge4# traceroute vpn 40 10.223.115.101 Traceroute 10.223.115.101 in VPN 40 traceroute to 10.223.115.101 (10.223.115.101), 30 hops max, 60 byte packets 1 * * * 2 * * * 3 * * * 4 * * * 5 * * *
作为解决方案,为了避免设置错误的TLOC下一跳信息,提出了以下方法:
policy lists tloc-list vedge1-tlocs tloc 10.155.0.118 color metro-ethernet encap ipsec tloc 10.155.0.118 color public-internet encap ipsec ! tloc-list vedge1-tlocs-preference tloc 10.155.0.118 color metro-ethernet encap ipsec preference 200 tloc 10.155.0.118 color public-internet encap ipsec preference 100 ! tloc-list vedge3-tlocs tloc 10.155.0.120 color metro-ethernet encap ipsec tloc 10.155.0.120 color public-internet encap ipsec ! tloc-list vedge3-tlocs-preference tloc 10.155.0.120 color metro-ethernet encap ipsec preference 150 tloc 10.155.0.120 color public-internet encap ipsec preference 50 ! ! ! policy control-policy TE_POLICY_2_SITE4 sequence 10 match route prefix-list SITE13_PREFIX tloc-list vedge1-tlocs ! action accept set tloc-list vedge1-tlocs-preference ! ! ! sequence 20 match route prefix-list SITE13_PREFIX tloc-list vedge3-tlocs ! action accept set tloc-list vedge3-tlocs-preference ! ! ! default-action accept ! !
此类策略可改善情况,防止通告具有错误TLOC下一跳的路由:
vsmart1# show omp routes 10.223.115.101/32 detail | nomore | b ADVERTISED | b "peer 10.155.0.50" | i Attributes\|originator\|\ tloc\|preference Attributes: originator 10.155.0.120 tloc 10.155.0.120, public-internet, ipsec preference 50 Attributes: originator 10.155.0.120 tloc 10.155.0.120, metro-ethernet, ipsec preference 150 Attributes: originator 10.155.0.120 tloc 10.155.0.120, public-internet, ipsec preference not set
因此,可保持整个故障场景的可达性:
vedge4# traceroute vpn 40 10.223.115.101 Traceroute 10.223.115.101 in VPN 40 traceroute to 10.223.115.101 (10.223.115.101), 30 hops max, 60 byte packets 1 192.168.40.6 (192.168.40.6) 0.458 ms 0.507 ms 0.617 ms 2 192.168.40.10 (192.168.40.10) 1.928 ms 1.976 ms 2.069 ms vedge4# ping vpn 40 10.223.115.101 Ping in VPN 40 PING 10.223.115.101 (10.223.115.101) 56(84) bytes of data. 64 bytes from 10.223.115.101: icmp_seq=1 ttl=254 time=0.702 ms 64 bytes from 10.223.115.101: icmp_seq=2 ttl=254 time=0.645 ms 64 bytes from 10.223.115.101: icmp_seq=3 ttl=254 time=0.691 ms 64 bytes from 10.223.115.101: icmp_seq=4 ttl=254 time=0.715 ms 64 bytes from 10.223.115.101: icmp_seq=5 ttl=254 time=0.603 ms ^C --- 10.223.115.101 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 4000ms rtt min/avg/max/mdev = 0.603/0.671/0.715/0.044 ms
版本 | 发布日期 | 备注 |
---|---|---|
1.0 |
10-Jun-2019 |
初始版本 |