Load balance not happening in BGP

[Sanjib Pradhan]

Dear Friends,

As per I know local BGP process may implement equal-cost load-balancing to the paths that:

• Have the same set of path attributes up to the MED (weight, Local Preference, Origin, MED)
• Are of the same type (both learned via iBGP or eBGP)
• Have the same IGP cost to reach their NEXT_HOP IP address

If the above conditions are met andmaximum-paths [ibgp]is  configured under the BGP process, BGP will install multiple equal-cost  routes into the local RIB and use them for load-balancing. We call the  above condition as load-balancing conditions for BGP.

As all the above criteria are matched still BGP is not doing load balance. Please find below routing table:

R1:

R1#sh ip bgp

BGP table version is 4, local router ID is 40.1.1.1

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

*>i192.168.1.0      20.1.1.2                 0    100      0 i

* i                        30.1.1.1                 0    100      0 i

R1#sh ip route

Gateway of last resort is not set

     20.0.0.0/24 is subnetted, 1 subnets

R       20.1.1.0 [120/1] via 10.1.1.2, 00:00:03, FastEthernet0/0

     40.0.0.0/24 is subnetted, 1 subnets

C       40.1.1.0 is directly connected, FastEthernet0/1

     10.0.0.0/24 is subnetted, 1 subnets

C       10.1.1.0 is directly connected, FastEthernet0/0

B    192.168.1.0/24 [200/0] via 20.1.1.2, 00:12:01

     30.0.0.0/24 is subnetted, 1 subnets

R       30.1.1.0 [120/1] via 40.1.1.2, 00:00:15, FastEthernet0/1

router bgp 100

no synchronization

bgp log-neighbor-changes

neighbor 10.1.1.2 remote-as 100

neighbor 40.1.1.2 remote-as 100

maximum-paths 2

no auto-summary

Please help....!!!!!!!   why BGP is not load balancing here????

R1#traceroute 192.168.1.1

Type escape sequence to abort.

Tracing the route to 192.168.1.1

  1 10.1.1.2 88 msec 60 msec 28 msec

  2 20.1.1.2 104 msec 56 msec 120 msec

Regards,

Sanjib

[Jon Marshall · Accepted solution]

Sanjib

Looking at your diagram all routers are in the same AS. If so this is IBGP and so under your BGP router config -

no maximum-paths 2

maximum-paths ibgp 2

Jon

[Sanjib Pradhan]

Dear Jon,

Thank you so much.

When I changed the configuration BGP is now loadbalancing. But in configuartion Max-path showing as 1 instead of 2.

R1#sh ip pro | sec bgp

Routing Protocol is "bgp 100"

  Outgoing update filter list for all interfaces is not set

  Incoming update filter list for all interfaces is not set

  IGP synchronization is disabled

  Automatic route summarization is disabled

  Neighbor(s):

    Address          FiltIn FiltOut DistIn DistOut Weight RouteMap

    12.1.1.2                                            

    13.1.1.3                                            

Maximum path: 1

  Routing Information Sources:

    Gateway         Distance      Last Update

    13.1.1.3             200      00:01:12

    12.1.1.2             200      00:02:15

  Distance: external 20 internal 200 local 200

Regards,

Sanjib