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设备型号及版本:S12504R R3608
问题描述:
125R设备作为MER设备,现场想要精简路由规格,因此在两台125R设备BGP视图下的ipv4地址族做路由聚合,发现聚合后右侧NE40-2设备访问server不通了,原因是MCR-2上路由指向MER2,MER2上路由指向黑洞,所以不通;红色为正常流量走向,绿色为不通时走向。
NE40-2(
NE40-2(
NE40-2(
NE40-2(
MER2上的路由:
<SDZZ-551J-4F-S12504R-SM-E006>dis ip routing-table vpn-instance IMS_RAN 11.6.0.0
Summary count : 1
Destination/Mask Proto Pre Cost NextHop Interface
11.6.0.0/16 BGP 130 0 127.0.0.1 NULL0
取消路由聚合后,正常网段路由指向MER1的,没有问题:
[SDZZ-551J-4F-S12504R-SM-E006-bgp-default-ipv4-IMS_RAN]undo aggregate 11.6.0.0 255.255.0.0
[SDZZ-551J-4F-S12504R-SM-E006-bgp-default-ipv4-IMS_RAN]dis ip routing-table vpn-instance IMS_RAN 11.6.0.0
Summary count : 1
Destination/Mask Proto Pre Cost NextHop Interface
11.6.0.0/24 BGP 255 0 10.53.221.5 RAGG1000.1000
MER-2上配了S-TRUNK的聚合口是down的,所以MER-2侧不会有终端的直连路由,只能通过MER-1的BGP学到,但是MER-2配了聚合以后看发布的路由下一跳是指向自己的,而不是MER-1,这个有点奇怪:
Route-Aggregation514
Current state: DOWN
Line protocol state: DOWN
Description: to_SDZZ-XiGang-S9312-SW1_TRUNK44:(IMS_RAN)
Maximum transmission unit: 1500
Internet protocol processing: Disabled
IP packet frame type: Ethernet II, hardware address: 78aa-82c8-1c01
IPv6 packet frame type: Ethernet II, hardware address: 78aa-82c8-1c01
Last clearing of counters: Never
Last 300 second input rate: 17 bytes/sec, 136 bits/sec, 0 packets/sec
Last 300 second output rate: 141 bytes/sec, 1128 bits/sec, 1 packets/sec
Input: 44801 packets, 11748433 bytes, - drops
Output: 1924604 packets, 176780102 bytes, - drops
分析发现属于现场配置问题:
现场MER2上符合路由聚合11.6.0.0/16的明细路由如下,有一部分是MER1发过来的路由(下一跳是RAGG1000.1000),还有一部分是MCR2发过来的路由(下一跳是RAGG999),此时就会有问题。如果把聚合路由改成11.6.0.0/21,这样MCR2发过来的明细路由就不会被聚合,就不会有问题
11.6.0.0/24 BGP 255 0 10.53.221.5 RAGG1000.1000
11.6.3.0/24 BGP 255 0 10.53.221.5 RAGG1000.1000
11.6.41.0/24 BGP 255 0 10.53.221.5 RAGG1000.1000
11.6.43.0/24 BGP 255 0 10.53.221.255 RAGG999
11.6.43.1/32 BGP 255 0 10.53.221.255 RAGG999
11.6.44.0/24 BGP 255 0 10.53.221.255 RAGG999
11.6.44.1/32 BGP 255 0 10.53.221.255 RAGG999
11.6.60.0/24 BGP 255 0 10.53.221.255 RAGG999
11.6.60.1/32 BGP 255 0 10.53.221.255 RAGG999
11.6.62.0/24 BGP 255 0 10.53.221.5 RAGG1000.1000
[SDZZ-551J-4F-S12504R-SM-E006-bgp-default-ipv4-IMS_RAN]DIS IP routing-table vpn-
instance IMS_RAN 11.6.0.0
Summary count : 1
Destination/Mask Proto Pre Cost NextHop Interface
11.6.0.0/16 BGP 130 0 127.0.0.1 NULL0
聚合掩码错误导致,错误地把上行MCR过来的路由也并到一起了,导致我们认为本地都有明细路由,所以此时聚合后的16位掩码路由直接置为黑洞了.
修正配置后解决.
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