[nsp] Load Balancing with BGP over unequal-cost circuits
Tay Chee Yong
tcy@pacific.net.sg
Wed, 2 Oct 2002 16:29:39 +0800 (Singapore Standard Time)
Hi Marcus,
Thanks for your mail. I do understand your point, just that I am curious at how
does the router cache the route in such a way that lesser routes will flow via
the 1Mbps and more traffic flowing via the 2Mbps.
Hope that the Cisco Engineers on this list and advise the location of the URL
that is explaining this.
Thanks.
Regards,
Cheeyong
On Wed, 2 Oct 2002, Marcus Keane wrote:
> Cheeyong,
>
> There's a doc on CCO that explains this but I can't seem to find it. :-(
> Basically, here, BGP isn't load sharing but the router is load sharing
> to the BGP next hop. All routes that your customer receives have a next
> hop of 192.168.255.202 and there are two static routes to this address
> using the two serials. Presumably this next hop is the loopback of the
> router at the other end and this configuration is duplicated on the
> other side. This is why you need the "ebgp-multihop" statement. Needless
> to say, this is imperfect load sharing as depending on the route-caching
> configuration, you will only load share sessions.
> Hope this helps.
> Marcus.
>
> -----Original Message-----
> From: Tay Chee Yong [mailto:tcy@pacific.net.sg]
> Sent: 02 October 2002 14:00
> To: cisco-nsp@puck.nether.net
> Subject: [nsp] Load Balancing with BGP over unequal-cost circuits
>
>
> 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
>
>
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