Description :

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

Architecture du lab :

BGP lab multipath

Configurations :

R1

 1 router bgp 1
 2  no synchronization
 3  bgp router-id 1.1.1.1
 4  bgp log-neighbor-changes
 5  neighbor 10.1.2.2 remote-as 234
 6  neighbor 10.1.3.3 remote-as 234
 7  neighbor 10.1.4.4 remote-as 234
 8  neighbor 10.1.5.5 remote-as 1
 9  neighbor 10.1.6.6 remote-as 1
10  maximum-paths 3
11  maximum-paths ibgp 3
12  no auto-summary

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

R5 & R6 aux IP prêts

1 router bgp 1
2  no synchronization
3  bgp router-id 5.5.5.5
4  bgp log-neighbor-changes
5  network 10.5.6.0 mask 255.255.255.0
6  neighbor 10.1.5.1 remote-as 1
7  no auto-summary

R2, R3 & R4 aux IP prêts

1 router bgp 234
2  no synchronization
3  bgp router-id 2.2.2.2
4  bgp log-neighbor-changes
5  network 10.0.234.0 mask 255.255.255.0
6  neighbor 10.1.2.1 remote-as 1
7  no auto-summary

Vérification :

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

 1 BGP table version is 9, local router ID is 1.1.1.1
 2 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
 3               r RIB-failure, S Stale
 4 Origin codes: i - IGP, e - EGP, ? - incomplete
 5  
 6    Network          Next Hop            Metric LocPrf Weight Path
 7 *  10.0.234.0/24    10.1.4.4                 0             0 234 i
 8 *                   10.1.3.3                 0             0 234 i
 9 *>                  10.1.2.2                 0             0 234 i
10 * i10.5.6.0/24      10.1.6.6                 0    100      0 i
11 *>i                 10.1.5.5                 0    100      0 i

il faut soit voir la TDR :

 1 R1#sh ip route
 2 Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
 3        D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
 4        N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
 5        E1 - OSPF external type 1, E2 - OSPF external type 2
 6        i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
 7        ia - IS-IS inter area, * - candidate default, U - per-user static route
 8        o - ODR, P - periodic downloaded static route
 9  
10 Gateway of last resort is not set
11  
12      1.0.0.0/32 is subnetted, 1 subnets
13 C       1.1.1.1 is directly connected, Loopback0
14      10.0.0.0/24 is subnetted, 7 subnets
15 C       10.1.3.0 is directly connected, FastEthernet1/3
16 B       10.5.6.0 [200/0] via 10.1.6.6, 00:01:09
17                  [200/0] via 10.1.5.5, 00:01:09
18 C       10.1.2.0 is directly connected, FastEthernet1/2
19 C       10.1.6.0 is directly connected, FastEthernet1/6
20 C       10.1.5.0 is directly connected, FastEthernet1/5
21 C       10.1.4.0 is directly connected, FastEthernet1/4
22 B       10.0.234.0 [20/0] via 10.1.4.4, 00:28:11
23                    [20/0] via 10.1.3.3, 00:28:11
24                    [20/0] via 10.1.2.2, 00:28:11

soit regarder la table BGP par réseau :

 1 R1#sh ip bgp 10.5.6.0
 2 BGP routing table entry for 10.5.6.0/24, version 9
 3 Paths: (2 available, best #2, table Default-IP-Routing-Table)
 4 Multipath: eBGP iBGP
 5   Advertised to update-groups:
 6         1
 7   Local
 8     10.1.6.6 from 10.1.6.6 (6.6.6.6)
 9       Origin IGP, metric 0, localpref 100, valid, internal, multipath
10   Local
11     10.1.5.5 from 10.1.5.5 (5.5.5.5)
12       Origin IGP, metric 0, localpref 100, valid, internal, multipath, best
 1 R1#sh ip bgp 10.0.234.0
 2 BGP routing table entry for 10.0.234.0/24, version 3
 3 Paths: (3 available, best #3, table Default-IP-Routing-Table)
 4 Multipath: eBGP iBGP
 5   Advertised to update-groups:
 6         1    2
 7   234
 8     10.1.4.4 from 10.1.4.4 (4.4.4.4)
 9       Origin IGP, metric 0, localpref 100, valid, external, multipath
10   234
11     10.1.3.3 from 10.1.3.3 (3.3.3.3)
12       Origin IGP, metric 0, localpref 100, valid, external, multipath
13   234
14     10.1.2.2 from 10.1.2.2 (2.2.2.2)
15       Origin IGP, metric 0, localpref 100, valid, external, multipath, best