BGP ECMP环境中community属性是如何传递的
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需求：R1发布环回口地址1.1.1.1给R2携带团体属性1111:1111，R3发布环回口地址1.1.1.1给R2携带团体属性1111:1111，R4发布1.1.1.1给R2不携带团体属性，测试在R2发送给R5的BGP路由表象中1.1.1.1是否携带团体属性值1111:1111?
AS规划：
R1 AS 100
R2 AS 200
R3 AS 300
R4 AS 400
R5 AS 500
拓扑环境：
R1配置：
<R1>dis ip int b
*down: administratively down
(s): spoofing (l): loopback
Interface Physical Protocol IP Address Description
GE0/0 up up 12.1.1.1 --
GE0/1 down down -- --
GE0/2 down down -- --
GE5/0 down down -- --
GE5/1 down down -- --
GE6/0 down down -- --
GE6/1 down down -- --
Loop0 up up(s) 1.1.1.1 --
Ser1/0 down down -- --
Ser2/0 down down -- --
Ser3/0 down down -- --
Ser4/0 down down -- --
<R1>dis cu conf bgp
#
bgp 100
peer 12.1.1.2 as-number 200
#
address-family ipv4 unicast
network 1.1.1.1 255.255.255.255 route-policy com
peer 12.1.1.2 enable
peer 12.1.1.2 advertise-community
#
<R1>dis cu conf route-policy
#
route-policy com permit node 10
apply community 1111:1111
#
returnR2配置：
<R2>dis ip int b
*down: administratively down
(s): spoofing (l): loopback
Interface Physical Protocol IP Address Description
GE0/0 up up 12.1.1.2 --
GE0/1 up up 23.1.1.2 --
GE0/2 up up 24.1.1.2 --
GE5/0 up up 25.1.1.2 --
GE5/1 down down -- --
GE6/0 down down -- --
GE6/1 down down -- --
Ser1/0 down down -- --
Ser2/0 down down -- --
Ser3/0 down down -- --
Ser4/0 down down -- --
<R2>
<R2>dis cu conf bgp
#
bgp 200
peer 12.1.1.1 as-number 100
peer 23.1.1.3 as-number 300
peer 24.1.1.4 as-number 400
peer 25.1.1.5 as-number 500
#
address-family ipv4 unicast
balance 32 //负载均衡配置
balance as-path-relax //忽略比较AS内容
peer 12.1.1.1 enable
peer 23.1.1.3 enable
peer 24.1.1.4 enable
peer 25.1.1.5 enable
peer 25.1.1.5 advertise-community
#R3配置：
<R3>dis ip int b
*down: administratively down
(s): spoofing (l): loopback
Interface Physical Protocol IP Address Description
GE0/0 down down -- --
GE0/1 up up 23.1.1.3 --
GE0/2 down down -- --
GE5/0 down down -- --
GE5/1 down down -- --
GE6/0 down down -- --
GE6/1 down down -- --
Loop0 up up(s) 1.1.1.1 --
Ser1/0 down down -- --
Ser2/0 down down -- --
Ser3/0 down down -- --
Ser4/0 down down -- --
<R3>
<R3>dis cu conf bgp
#
bgp 300
peer 23.1.1.2 as-number 200
#
address-family ipv4 unicast
network 1.1.1.1 255.255.255.255 route-policy com
peer 23.1.1.2 enable
peer 23.1.1.2 advertise-community
#
return
<R3>
<R3>dis cu conf route-po
<R3>dis cu conf route-policy
#
route-policy com permit node 10
apply community 1111:1111
#R4配置：
<R4>dis ip int b
*down: administratively down
(s): spoofing (l): loopback
Interface Physical Protocol IP Address Description
GE0/0 down down -- --
GE0/1 down down -- --
GE0/2 up up 24.1.1.4 --
GE5/0 down down -- --
GE5/1 down down -- --
GE6/0 down down -- --
GE6/1 down down -- --
Loop0 up up(s) 1.1.1.1 --
Ser1/0 down down -- --
Ser2/0 down down -- --
Ser3/0 down down -- --
Ser4/0 down down -- --
<R4>
<R4>dis cu conf bgp
#
bgp 400
peer 24.1.1.2 as-number 200
#
address-family ipv4 unicast
network 1.1.1.1 255.255.255.255
peer 24.1.1.2 enable
#
returnR5配置：
<R5>dis ip int b
*down: administratively down
(s): spoofing (l): loopback
Interface Physical Protocol IP Address Description
GE0/0 down down -- --
GE0/1 down down -- --
GE0/2 down down -- --
GE5/0 up up 25.1.1.5 --
GE5/1 down down -- --
GE6/0 down down -- --
GE6/1 down down -- --
Ser1/0 down down -- --
Ser2/0 down down -- --
Ser3/0 down down -- --
Ser4/0 down down -- --
<R5>dis cu conf bgp
#
bgp 500
peer 25.1.1.2 as-number 200
#
address-family ipv4 unicast
peer 25.1.1.2 enable
#
return测试：
在R2上查看BGP ECMP负载情况：
<R2>dis bgp peer ipv4
BGP local router ID: 25.1.1.2
Local AS number: 200
Total number of peers: 4 Peers in established state: 4
* - Dynamically created peer
Peer AS MsgRcvd MsgSent OutQ PrefRcv Up/Down State
12.1.1.1 100 22 20 0 1 00:13:08 Established
23.1.1.3 300 23 21 0 1 00:13:08 Established
24.1.1.4 400 20 19 0 1 00:13:08 Established
25.1.1.5 500 3 4 0 0 00:00:25 Established
<R2>dis bgp routing-table ipv4 //通过在R2上查看路由，确认是负载均衡状态
Total number of routes: 3
BGP local router ID is 25.1.1.2
Status codes: * - valid, > - best, d - dampened, h - history
s - suppressed, S - stale, i - internal, e - external
a - additional-path
Origin: i - IGP, e - EGP, ? - incomplete
Network NextHop MED LocPrf PrefVal Path/Ogn
* >e 1.1.1.1/32 12.1.1.1 0 0 100i
* >e 23.1.1.3 0 0 300i
* >e 24.1.1.4 0 0 400i
<R2>
<R2>dis ip routing-table
Destinations : 25 Routes : 27
Destination/Mask Proto Pre Cost NextHop Interface
0.0.0.0/32 Direct 0 0 127.0.0.1 InLoop0
1.1.1.1/32 BGP 255 0 12.1.1.1 GE0/0
23.1.1.3 GE0/1
24.1.1.4 GE0/2
12.1.1.0/24 Direct 0 0 12.1.1.2 GE0/0R5上查看收到的1.1.1.1的路由条目属性值，发现携带了1111：1111的团体属性值
<R5>dis bgp routing-table ipv4 1.1.1.1
BGP local router ID: 25.1.1.5
Local AS number: 500
Paths: 1 available, 1 best
BGP routing table information of 1.1.1.1/32:
From : 25.1.1.2 (25.1.1.2)
Rely nexthop : 25.1.1.2
Original nexthop: 25.1.1.2
OutLabel : NULL
Community : <1111:1111>
RxPathID : 0x0
TxPathID : 0x0
AS-path : 200 100
Origin : igp
Attribute value : pref-val 0
State : valid, external, best
IP precedence : N/A
QoS local ID : N/A
Traffic index : N/A开启R5侧debug，确认R5侧收到BGP update更新报文是否携带团体属性值-------答案是携带团体属性1111:1111
<R5>t m
The current terminal is enabled to display logs.
<R5>t d
The current terminal is enabled to display debugging logs.
<R5>deb
<R5>debugging bgp u
<R5>debugging bgp update
<R5>reset bgp all
Reset BGP sessions? [Y/N]:y
<R5>%Jan 4 01:51:15:752 2020 R5 BGP/5/BGP_STATE_CHANGED:
BGP default.: 25.1.1.2 state has changed from ESTABLISHED to IDLE for administrative reset.
<R5>%Jan 4 01:51:18:002 2020 R5 BGP/5/BGP_STATE_CHANGED:
BGP default.: 25.1.1.2 State is changed from OPENCONFIRM to ESTABLISHED.
<R5>
<R5>*Jan 4 01:51:18:228 2020 R5 BGP/7/DEBUG:
BGP.: Recv UPDATE from peer 25.1.1.2 with following destinations:
Update message length : 59
Origin : IGP
AS path : 200 100
Next hop : 25.1.1.2
Community : <1111:1111>
1.1.1.1/32 PathID 0 ,结论：在EBGP ECMP负载均衡环境中，当不同的EBGP 宣告者分别发布既带有团体属性的community属性值和不带团体属性的community属性的业务网段时，最终EBGP 用户侧设备会收到一条带有团体community属性的路由，而不带community属性值得路由条目会被忽略掉
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