Return traffic issue in BGP when multiple isp bandwidth in single router.

[csawest.dc]

Dear Experts,

Please help me regarding return traffic in bgp when multiple isp's in single router.

we ar using multiple isp's bandwidth in single router

ISP-A   45 mb
ISP-B  24 mb

we have our own ASN and two registerd ip pools  from APNIC

e.g ASN : 123456 ( 4 byte)

IP Pools : 124.59.62.0/22
                27.152.131.0/22

we are advertised all the ip pools (both ip pools) in both the ISP's via eBGP.

we are facing the problem about return traffic we can manage outbound  traffic through route-map ,how many ips of outbound traffice through which ISP that can be manage from our side our problem is most of the traffic used via ISP-A up to 42 to 44 mb continue but ISP-A used only 8 to 10 mb bandwidth maximum

we need when outbound traffic of which ip pools through ISP-B same as return traffic through ISP-B and for the same as ISP-A
but when ISP-B bandwidth goes down my all the traffic through ISP-A visa-versa.

but at present i am not able to achive this many times i tried but faild to achive this my required.

i also configure as-path prepend but not able to achive of return traffic from perticular ISP. but must i need it.

my router id is ISP-B WAN ip but not return traffic through ISP-B most of the returen traffic at present through ISP-A

please help it's very very helpfull for me.

Thans in ADV

[Dan-Ciprian Cicioiu]

Hi ,

Could you post the curent bgp config

Dan

[Mahesh Gohil · Accepted solution]

Hi,

So you want to control bw used between ISP-A and ISP-B and it's good that you have announced all your Pool
to both of ISP. Now control is with you.

Now to affect incoming bw the approach is little manual. You need to identify which pool cater more traffic.

For example: Divide below pool in different /24 subnets

124.59.62.0/22 AND 27.152.131.0/22

to

124.59.60.0/24
124.59.61.0/24
124.59.62.0/24
124.59.63.0/24

27.152.128.0/24
27.152.129.0/24
27.152.130.0/24
27.152.131.0/24

and then prepare prefix-list/route-map

ip prefix-list ISP-A-PRIMARY permit 124.59.60.0/24
ip prefix-list ISP-A-PRIMARY permit 124.59.61.0/24
ip prefix-list ISP-A-PRIMARY permit 124.59.62.0/24
ip prefix-list ISP-A-PRIMARY permit 124.59.63.0/24

ip prefix-list ISP-B-PRIMARY permit 27.152.128.0/24
ip prefix-list ISP-B-PRIMARY permit 27.152.129.0/24
ip prefix-list ISP-B-PRIMARY permit 27.152.130.0/24
ip prefix-list ISP-B-PRIMARY permit 27.152.131.0/24

route-map ISP-A permit 10
match ip address prefix-list ISP-A-PRIMARY

route-map ISP-A permit 20
match ip address prefix-list ISP-B-PRIMARY
set as-path prepend 123456 123456 123456

router bgp 123456
neighbor x.x.x.x (ISP-A peering ip) route-map ISP-A out

Same way for ISP-B but it is in reverse.

route-map ISP-B permit 10
match ip address prefix-list ISP-B-PRIMARY

route-map ISP-B permit 20
match ip address prefix-list ISP-A-PRIMARY
set as-path prepend 123456 123456 123456

router bgp 123456

neighbor x.x.x.x (ISP-B peering ip) route-map ISP-B out

Now if you see ISP-A is having more traffic then ISP-B you remove one pool from prefix-list ISP-A-PRIMARY and
add it in prefix list ISP-B-PRIMARY..

like

no ip prefix-list ISP-A-PRIMARY permit 124.59.63.0/24
ip prefix-list ISP-B-PRIMARY permit 124.59.63.0/24

this way you are shifting incoming traffic for pool 124.59.63.0/24 from ISP-A to ISP-B. You can do this practice for other pool and see behavor of traffic

please feel free to write if you have more query

Regards
Mahesh

[csawest.dc]

Dear Mahesh,

Thanks a lot for your great help i am very appreciat for this.

I think you belongs to Gujarat , i am also same.

at present we are configured ip-prefix-list as per given bellow

my router LAN ip gi0/1

ip add 124.59.60.1 255.255.255.192

124.59.60.64/26 for ISP-B -
124.59.60.128/25  for ISP-B
124.59.61.0/24 for ISP-A
124.59.62.0/24 for ISP-A

124.59.63.0/26 for ISP-A

124.59.63.64/26 for ISP- B

124.59.63.128/25 for ISP A

same ip pools with mask for outbound through route-map

and bellow ip pools not used at present just advertise in both the isp's but not used at present.

27.152.128.0/24
27.152.129.0/24
27.152.130.0/24
27.152.131.0/24

i will try to do as per your templates and then let you know within few days.

Thanks once again!!!

[saimbt]

Hi,

One more thing worth checking would be the local preference configured for your prefixes by both your ISPs. In all liklihood both your ISPs might have a common upstream provider and since the ISP's might have configured the local preference the upstream provider might be taken the decision that might not be beneficial for you. Ask the providers to use the same local preference as they use for other customers and let the traffic decision happen on the basis on AS-prepend attribute.

Sai.

[Mahesh Gohil]

Hi Sai,

Thanks for pointing out...

But normally provider always keep higher local preference towards his directly connected customer to ensure traffic do not move via. upstream

provider.

thanks again

Regards

Mahesh

[saimbt]

I compleyely agree, the issue with local preference comes into picture with both the downstream ISP's have peering with the same upstream provider. I came across this issue with two ISP's in India.

Sai.

[csawest.dc]

Dear Experts,

Should i configure as per given by mahesh and then can i achive my require of inbound traffic (return traffic) from  ISP B for selected pools ??

Thanks in ADV,