组网:S12508X-AF做Border,下行四条聚合链路到四台接入设备。
型号及版本:S12508X-AF 2713
问题描述:boeder出方向流量ecmp到四台设备,但绝大部分流量只走了其中一条链路。
查看诊断,发现设备路由表、fib表正常,端口状态正常。
1)缺省路由指向四个ecmp下一跳地址,路由表项正常
===============display ip routing-table===============
Destination/Mask Proto Pre Cost NextHop Interface
0.0.0.0/0 Static 60 0 22.247.129.185 RAGG10
22.247.130.185 RAGG11
22.247.131.185 RAGG12
22.247.132.185 RAGG13
2)fib表项存在4个下一跳,fib表项正常,border出方向到四台接入流量会从四个聚合口发出
===============display fib===============
Flag:
U:Useable G:Gateway H:Host B:Blackhole D:Dynamic S:Static
R:Relay F:FRR
Destination/Mask Nexthop Flag OutInterface/Token Label
0.0.0.0/0 22.247.129.185 USGR RAGG10 Null
0.0.0.0/0 22.247.130.185 USGR RAGG11 Null
0.0.0.0/0 22.247.131.185 USGR RAGG12 Null
0.0.0.0/0 22.247.132.185 USGR RAGG13 Null
3)查看4个聚合口,发现状态正常,物理口无错包,且RAGG10、12、13出方向存在流量,说明设备转发无异常,系出方向流量hash不均。
Route-Aggregation10
Current state: UP
Line protocol state: UP
Bandwidth: 20000000 kbps
…
Last clearing of counters: Never
Last 300 seconds input rate: 344196098 bytes/sec, 2753568784 bits/sec, 293320 packets/sec
Last 300 seconds output rate: 461 bytes/sec, 3688 bits/sec, 2 packets/sec
1229868796710 packets input, 1519504471426558 bytes, 0 drops
414772985 packets output, 117127975548 bytes, 0 drops
Route-Aggregation11
Current state: UP
Line protocol state: UP
Bandwidth: 20000000 kbps
…
Last clearing of counters: Never
Last 300 seconds input rate: 347567148 bytes/sec, 2780537184 bits/sec, 294616 packets/sec
Last 300 seconds output rate: 1185114531 bytes/sec, 9480916248 bits/sec, 985318 packets/sec
1305005829539 packets input, 1646712613329673 bytes, 0 drops
2303856336959 packets output, 1398568434514094 bytes, 0 drops
Route-Aggregation12
Current state: UP
Line protocol state: UP
Bandwidth: 20000000 kbps
…
Last clearing of counters: Never
Last 300 seconds input rate: 381647810 bytes/sec, 3053182480 bits/sec, 318532 packets/sec
Last 300 seconds output rate: 683 bytes/sec, 5464 bits/sec, 5 packets/sec
1203296471569 packets input, 1500229760508660 bytes, 0 drops
206007644 packets output, 32768301421 bytes, 0 drops
Route-Aggregation13
Current state: UP
Line protocol state: UP
Bandwidth: 20000000 kbps
…
Last clearing of counters: Never
Last 300 seconds input rate: 353941353 bytes/sec, 2831530824 bits/sec, 300559 packets/sec
Last 300 seconds output rate: 1126 bytes/sec, 9008 bits/sec, 9 packets/sec
1301731640239 packets input, 1634942752705068 bytes, 0 drops
269080411 packets output, 39172508469 bytes, 0 drops
4)经过确认,为保持软件实现方式的一致,该型号版本的设备默认情况下根据报文外层头部进行哈希,在VXLAN组网中,设备作为Border、leaf等角色对vxlan报文解封装后,报文无法根据VXLAN外层头部进行负载分担,因此出现上述流量哈希不均的现象,可修改配置为Tunnel all,使设备根据内外层报文头部进行hash,实现出方向流量的负载分担。
解决方发:可以通过配置ip load-sharing mode per-flow tunnel all global或者link-aggregation global load-sharing tunnel all命令,使设备同时根据内外层报文头部进行负载分担转发。两条命令效果相同,配置一条即可解决,后配置的命令生效。
注意: 修改设备负载分担方式不会引发断流,只会使流量会重新计算负载出接口,哈希负载转发路径会发生变化。
实验室实测如下
1、
2、
流量目的地址是2.0.0.2,从路由表看,到改地址有4个下一跳:
测试仪打入变化的报文,缺省情况下,出方向流量只走了两个下一跳:
全局配置ip load-sharing mode per-flow tunnel all global命令,流量可以从4个下一跳均HASH出去:
从测试仪观察流量,配置命令过程中无丢包:
3、
配置ip load-sharing mode per-flow tunnel all global 命令后流量负载分担,且过程中无丢包。
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