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BGP between 2 ISP links with auto failover & load balancing

Unanswered Question
Mar 12th, 2012
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Dear friends, plz help in following scenerio.

My company have 7 locations all over India.We had a link from one ISP.Now, my company want to a link from other ISP which would be act as back up in case of primary goes down & can use in load balancing facility.

My doubts:

1. My doubt is can a BGp router has 2 AS since, in this case , both ISPs would provide me 2 AS.

2. How can I configure load balancing in BGP?

3. How can I configure auto failover ?

PLz guide me

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Overall Rating: 0 (0 ratings)
r.malviya Tue, 03/13/2012 - 01:16
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Hi Abhi ,


1) You no need to use 2 AS no .

ISP 1 (AS 100)                ISP 2(AS 200)

            |                                   |

            |                                   |

                       U R (AS 300)

U can't do Ioadbalancing in BGP like other routing protocol do .

Sample config


interface Serial 0
ip address
no ip route-cache
interface Serial 1
ip address
no ip route-cache
router bgp 300
neighbor remote-as 100
neighbor route-map UPDATES-1 in

!--- This allows only the networks up to

neighbor remote-as 200
neighbor route-map UPDATES-2 in

!--- This allows anything above the network.

route-map UPDATES-1 permit 10
match ip address 1
set weight 100

route-map UPDATES-1 permit 20
match ip address 2
route-map UPDATES-2 permit 10
match ip address 1
route-map UPDATES-2 permit 20
match ip address 2
set weight 100
access-list 1 permit
access-list 2 deny
access-list 2 permit any

There are other paramiter as well you can set to influance the incoming & outgoing traffic

like u can set local Pref/weight attribute for outgoing
& AS Path prepand for incoming traffic as well .




needtechhelp Tue, 03/13/2012 - 02:50
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Ritesh, Thanks for answer.

There is one command in BGp : Maximum-path =

can I use the same for load balancing?

amigomnemonik Tue, 03/13/2012 - 03:04
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Load balancing works only if you have 2 peer connections to the same AS number. Filtering prefixes via route maps and attaching them to the neighbour statements seems to be the best option.

Sent from my iPhone

r.malviya Tue, 03/13/2012 - 07:18
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How can I configure auto failover ?

Auto failover is always there becasue when u config both off the ISP , So on u r router u can see u are getting the same prefix from 2 different Next-hop(or ISP)

it will use only one as best & next will be ideal ,

when u r primary will down u still have same prefix from other ISP in bgp table

& automatically it will install in routing table .




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