[nsp] Load Balancing with BGP over unequal-cost circuits

[Tay Chee Yong]

Hi all,

My understanding is that BGP doesn't do load balancing because of its nature of
selection of best path, however load sharing can be achieved.

I have a customer who is doing load balancing over an E1 (2Mbps) and a 1Mbps
circuit (unequal bandwidth) using BGP, and it seems to work.

Could someone advise how was the load-balancing achieved?

Following is the config :

* Note : Both circuits are terminated to the same router on both ends. *

interface Loopback0
 ip address 172.16.255.10 255.255.255.255
!

interface Serial0/1
 description ==> Link 1Mbps
 bandwidth 1024
 ip address 192.168.252.206 255.255.255.252
 no ip redirects
 no ip proxy-arp
 ip load-sharing per-packet
 no fair-queue
 hold-queue 4096 out
!
interface Serial0/2
 description ==> Link 2Mbps
 bandwidth 2048
 ip address 192.168.252.202 255.255.255.252
 no ip redirects
 no ip proxy-arp
 ip load-sharing per-packet
 no fair-queue
 hold-queue 1024 out
!

 network 172.16.0.0 mask 255.255.192.0
 network 172.16.64.0 mask 255.255.192.0
 network 172.16.128.0 mask 255.255.192.0
 network 172.16.192.0 mask 255.255.192.0
 neighbor 192.168.255.202 remote-as 65500
 neighbor 192.168.255.202 ebgp-multihop 3
 neighbor 192.168.255.202 update-source Loopback0
 neighbor 192.168.255.202 version 4
 neighbor 192.168.255.202 soft-reconfiguration inbound
 neighbor 192.168.255.202 route-map ksc-in in
 neighbor 192.168.255.202 route-map ksc-out out

ip route 172.16.0.0 255.255.192.0 Null0
ip route 172.16.64.0 255.255.192.0 Null0
ip route 172.16.128.0 255.255.192.0 Null0
ip route 172.16.192.0 255.255.192.0 Null0
ip route 192.168.255.202 255.255.255.255 Serial0/1
ip route 192.168.255.202 255.255.255.255 Serial0/2


access-list 21 permit any
access-list 22 permit 172.16.0.0 0.0.255.255

route-map ksc-out permit 10
 match ip address 22
!

route-map ksc-in permit 10
 match ip address 21
 set local-preference 500
!

Serial0/1 is up, line protocol is up
  Hardware is DSCC4 Serial
  Description: ==> Link 1Mbps
  Internet address is 192.168.252.206/30
  MTU 1500 bytes, BW 1024 Kbit, DLY 20000 usec,
     reliability 255/255, txload 242/255, rxload 211/255
  Encapsulation HDLC, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:00, output 00:00:05, output hang never
  Last clearing of "show interface" counters 18:14:54
  Queueing strategy: fifo
  Output queue 971/4096, 138782 drops; input queue 0/75, 54 drops
  5 minute input rate 848000 bits/sec, 213 packets/sec
  5 minute output rate 973000 bits/sec, 345 packets/sec

Serial0/2 is up, line protocol is up
  Hardware is DSCC4 Serial
  Description: ==> Link 2Mbps
  Internet address is 192.168.252.202/30
  MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec,
     reliability 255/255, txload 211/255, rxload 209/255
  Encapsulation HDLC, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:08, output 00:00:09, output hang never
  Last clearing of "show interface" counters 18:17:34
  Queueing strategy: fifo
  Output queue 1023/1024, 3212912 drops; input queue 0/75, 60 drops
  5 minute input rate 1686000 bits/sec, 425 packets/sec
  5 minute output rate 1702000 bits/sec, 517 packets/sec


Thanks.

Regards,
Cheeyong