Description :

Nous allons voir le partage de charge BGP au travers du multipath.

Architecture du lab :

BGP lab multipath

Configurations :

R1

router bgp 1
 no synchronization
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 neighbor 10.1.2.2 remote-as 234
 neighbor 10.1.3.3 remote-as 234
 neighbor 10.1.4.4 remote-as 234
 neighbor 10.1.5.5 remote-as 1
 neighbor 10.1.6.6 remote-as 1
 maximum-paths 3
 maximum-paths ibgp 3
 no auto-summary

maximum-paths 3 => path eBGP
maximum-paths ibgp 3 => path iBGP

R5 & R6 aux IP prêts

router bgp 1
 no synchronization
 bgp router-id 5.5.5.5
 bgp log-neighbor-changes
 network 10.5.6.0 mask 255.255.255.0
 neighbor 10.1.5.1 remote-as 1
 no auto-summary

R2, R3 & R4 aux IP prêts

router bgp 234
 no synchronization
 bgp router-id 2.2.2.2
 bgp log-neighbor-changes
 network 10.0.234.0 mask 255.255.255.0
 neighbor 10.1.2.1 remote-as 1
 no auto-summary

Vérification :

Le show ip bgp sur R1 n’est pas trés parlant :

BGP table version is 9, 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
*  10.0.234.0/24    10.1.4.4                 0             0 234 i
*                   10.1.3.3                 0             0 234 i
*>                  10.1.2.2                 0             0 234 i
* i10.5.6.0/24      10.1.6.6                 0    100      0 i
*>i                 10.1.5.5                 0    100      0 i

il faut soit voir la TDR :

R1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route
 
Gateway of last resort is not set
 
     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback0
     10.0.0.0/24 is subnetted, 7 subnets
C       10.1.3.0 is directly connected, FastEthernet1/3
B       10.5.6.0 [200/0] via 10.1.6.6, 00:01:09
                 [200/0] via 10.1.5.5, 00:01:09
C       10.1.2.0 is directly connected, FastEthernet1/2
C       10.1.6.0 is directly connected, FastEthernet1/6
C       10.1.5.0 is directly connected, FastEthernet1/5
C       10.1.4.0 is directly connected, FastEthernet1/4
B       10.0.234.0 [20/0] via 10.1.4.4, 00:28:11
                   [20/0] via 10.1.3.3, 00:28:11
                   [20/0] via 10.1.2.2, 00:28:11

soit regarder la table BGP par réseau :

R1#sh ip bgp 10.5.6.0
BGP routing table entry for 10.5.6.0/24, version 9
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Multipath: eBGP iBGP
  Advertised to update-groups:
        1
  Local
    10.1.6.6 from 10.1.6.6 (6.6.6.6)
      Origin IGP, metric 0, localpref 100, valid, internal, multipath
  Local
    10.1.5.5 from 10.1.5.5 (5.5.5.5)
      Origin IGP, metric 0, localpref 100, valid, internal, multipath, best
R1#sh ip bgp 10.0.234.0
BGP routing table entry for 10.0.234.0/24, version 3
Paths: (3 available, best #3, table Default-IP-Routing-Table)
Multipath: eBGP iBGP
  Advertised to update-groups:
        1    2
  234
    10.1.4.4 from 10.1.4.4 (4.4.4.4)
      Origin IGP, metric 0, localpref 100, valid, external, multipath
  234
    10.1.3.3 from 10.1.3.3 (3.3.3.3)
      Origin IGP, metric 0, localpref 100, valid, external, multipath
  234
    10.1.2.2 from 10.1.2.2 (2.2.2.2)
      Origin IGP, metric 0, localpref 100, valid, external, multipath, best