BGP路由反射器

 

当一个as中包含的ibgp对等体太多时，配置全互联就比较麻烦，这时候可以起路由反射器。将一个路由器配置成路由反射器(RR)，其他的ibgp路由器当做客户，这些客户只与RR建立对等体关系，而不是与另外的每个路由器对等。(可以大大的减少配置)

反躲规则：
1）如果路由是从非客户过来则反躲给客户，不会给非客户；
2）如果路由是从客户过来，会反射给客户和非客户；
3）如果路由是从EBGP邻居过来，反射给客户和非客户。

!
hostname R1
!
router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0
!
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 network 172.16.1.0 mask 255.255.255.0
 network 172.16.2.0 mask 255.255.255.0
 network 172.16.3.0 mask 255.255.255.0
 neighbor 2.2.2.2 remote-as 100
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 3.3.3.3 remote-as 100
 neighbor 3.3.3.3 update-source Loopback0
 neighbor 3.3.3.3 route-reflector-client
 neighbor 4.4.4.4 remote-as 100
 neighbor 4.4.4.4 update-source Loopback0
 no auto-summary

!
hostname R2
!
router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0
!
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 network 172.16.1.0 mask 255.255.255.0
 network 172.16.4.0 mask 255.255.255.0
 network 172.16.5.0 mask 255.255.255.0
 neighbor 1.1.1.1 remote-as 100
 neighbor 1.1.1.1 update-source Loopback0
 neighbor 1.1.1.1 route-reflector-client
 neighbor 3.3.3.3 remote-as 100
 neighbor 3.3.3.3 update-source Loopback0
 neighbor 3.3.3.3 route-reflector-client
 neighbor 4.4.4.4 remote-as 100
 neighbor 4.4.4.4 update-source Loopback0
 no auto-summary

 

!
hostname R3
!
router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 passive-interface Serial1/0
 network 0.0.0.0 255.255.255.255 area 0
!        
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 neighbor 1.1.1.1 remote-as 100
 neighbor 1.1.1.1 update-source Loopback0
 neighbor 2.2.2.2 remote-as 100
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 172.16.6.5 remote-as 200
 no auto-summary

!
hostname R4
!
router ospf 1
 router-id 4.4.4.4
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0
!        
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 neighbor 1.1.1.1 remote-as 100
 neighbor 1.1.1.1 update-source Loopback0
 neighbor 2.2.2.2 remote-as 100
 neighbor 2.2.2.2 update-source Loopback0
 no auto-summary

!
hostname R5
!
router bgp 200
 no synchronization
 bgp log-neighbor-changes
 network 172.16.6.0 mask 255.255.255.0
 network 192.168.1.0
 network 192.168.2.0
 neighbor 172.16.6.3 remote-as 100
 no auto-summary

R4#show ip bgp
BGP table version is 25, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
r i172.16.1.0/24    2.2.2.2                  0    100      0 i
r>i                 1.1.1.1                  0    100      0 i
r i172.16.2.0/24    1.1.1.1                  0    100      0 i
r>i                 1.1.1.1                  0    100      0 i
r i172.16.3.0/24    1.1.1.1                  0    100      0 i
r>i                 1.1.1.1                  0    100      0 i
r>i172.16.4.0/24    2.2.2.2                  0    100      0 i
r>i172.16.5.0/24    2.2.2.2                  0    100      0 i
r i172.16.6.0/24    172.16.6.5               0    100      0 200 i
r>i                 172.16.6.5               0    100      0 200 i
*>i192.168.1.0      172.16.6.5               0    100      0 200 i
* i                 172.16.6.5               0    100      0 200 i
*>i192.168.2.0      172.16.6.5               0    100      0 200 i
* i                 172.16.6.5               0    100      0 200 i

 

R4#show ip bgp 192.168.1.0
BGP routing table entry for 192.168.1.0/24, version 24
Paths: (2 available, best #1, table Default-IP-Routing-Table)
  Not advertised to any peer
  200
    172.16.6.5 (metric 192) from 1.1.1.1 (1.1.1.1)
      Origin IGP, metric 0, localpref 100, valid, internal, best
      Originator: 3.3.3.3, Cluster list: 1.1.1.1
  200
    172.16.6.5 (metric 192) from 2.2.2.2 (2.2.2.2)
      Origin IGP, metric 0, localpref 100, valid, internal
      Originator: 3.3.3.3, Cluster list: 2.2.2.2

 

为了节省开销，当在同一个区域时，两 个RR中通过指定同一个cluster-id，可以节省内存存放学过来的路由条目，因为缺省情况下，一个RR就是一个cluster，这个两 个RR之间相互发放路由，就多出一倍，如果将两 个RR同指定为一个cluster后，就可以减少开销

R1(config-router)#bgp cluster-id 1
R2(config-router)#bgp cluster-id 1

在没有指定之前：
R1#show ip bgp
BGP table version is 35, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
* i172.16.1.0/24    2.2.2.2                  0    100      0 i
*>                  0.0.0.0                  0         32768 i
*> 172.16.2.0/24    0.0.0.0                  0         32768 i
*> 172.16.3.0/24    0.0.0.0                  0         32768 i
r>i172.16.4.0/24    2.2.2.2                  0    100      0 i
r>i172.16.5.0/24    2.2.2.2                  0    100      0 i
r i172.16.6.0/24    172.16.6.5               0    100      0 200 i
r>i                 172.16.6.5               0    100      0 200 i
* i192.168.1.0      172.16.6.5               0    100      0 200 i
*>i                 172.16.6.5               0    100      0 200 i
* i192.168.2.0      172.16.6.5               0    100      0 200 i
*>i                 172.16.6.5               0    100      0 200 i

R2#show ip bgp
BGP table version is 26, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
* i172.16.1.0/24    1.1.1.1                  0    100      0 i
*>                  0.0.0.0                  0         32768 i
r>i172.16.2.0/24    1.1.1.1                  0    100      0 i
r>i172.16.3.0/24    1.1.1.1                  0    100      0 i
*> 172.16.4.0/24    0.0.0.0                  0         32768 i
*> 172.16.5.0/24    0.0.0.0                  0         32768 i
r i172.16.6.0/24    172.16.6.5               0    100      0 200 i
r>i                 172.16.6.5               0    100      0 200 i
* i192.168.1.0      172.16.6.5               0    100      0 200 i
*>i                 172.16.6.5               0    100      0 200 i
* i192.168.2.0      172.16.6.5               0    100      0 200 i
*>i                 172.16.6.5               0    100      0 200 i

 

指定之后：

R1#show ip bgp
BGP table version is 35, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
* i172.16.1.0/24    2.2.2.2                  0    100      0 i
*>                  0.0.0.0                  0         32768 i
*> 172.16.2.0/24    0.0.0.0                  0         32768 i
*> 172.16.3.0/24    0.0.0.0                  0         32768 i
r>i172.16.4.0/24    2.2.2.2                  0    100      0 i
r>i172.16.5.0/24    2.2.2.2                  0    100      0 i
r>i172.16.6.0/24    172.16.6.5               0    100      0 200 i
*>i192.168.1.0      172.16.6.5               0    100      0 200 i
*>i192.168.2.0      172.16.6.5               0    100      0 200 i

R2#show ip bgp
BGP table version is 26, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
* i172.16.1.0/24    1.1.1.1                  0    100      0 i
*>                  0.0.0.0                  0         32768 i
r>i172.16.2.0/24    1.1.1.1                  0    100      0 i
r>i172.16.3.0/24    1.1.1.1                  0    100      0 i
*> 172.16.4.0/24    0.0.0.0                  0         32768 i
*> 172.16.5.0/24    0.0.0.0                  0         32768 i
r>i172.16.6.0/24    172.16.6.5               0    100      0 200 i
*>i192.168.1.0      172.16.6.5               0    100      0 200 i
*>i192.168.2.0      172.16.6.5               0    100      0 200 i

 

 

在R4上看到：
R4#show ip bgp 192.168.1.0
BGP routing table entry for 192.168.1.0/24, version 33
Paths: (2 available, best #1, table Default-IP-Routing-Table)
  Not advertised to any peer
  200
    172.16.6.5 (metric 192) from 1.1.1.1 (1.1.1.1)
      Origin IGP, metric 0, localpref 100, valid, internal, best
      Originator: 3.3.3.3, Cluster list: 0.0.0.1
  200
    172.16.6.5 (metric 192) from 2.2.2.2 (2.2.2.2)
      Origin IGP, metric 0, localpref 100, valid, internal
      Originator: 3.3.3.3, Cluster list: 0.0.0.1