Load balancing using single /24 in BGP

[jayaramakrishnan]

Hi,

I have 2 internet link and only one /24 subnet and running bgp between 2 service provider. Now i want to use both link in active. Is there any option avilable in BGP to use load balance.

[vdadlaney]

Hi Jayaramakrishnan,

One solution that you could use is split the /24 into 2 x /25's and than advertise one /25 out of one link and the other out of the other link. In addition pls also advertise the /24 out of both links for backup purposes in case one of your ISP fails all traffic inbound for the /25 associated with the failed ISP will follow the /24 that you advertised out of the other ISP. HTH.

Regards,

Vikram

[Mahesh Gohil · Accepted solution]

Hello Vikram,

A little correction to your reply.

ISP will not accept any route with /25 subnet. consider below

                 ---ISPA--

Upstream               Customer

                ---ISPB---

If customer has advt. /25 and assume that ISPA and ISPB has accepted as an optional case. it is not guarantee that upstream will accept

prefix in /25 subnet as a result upstream will see only one /24 as a best either via.ISPA or ISPB

This is possible only if customer is peered with single provider.

There is no solution to loadshare traffic. The only option left is customer asks local registry for /23 subnet and divide it into /24 subnet

Hope this helps

Regards

Mahesh

[vdadlaney]

Hi Mahesh,

Thx for correcting me on that. I forgot that little fact about the ISP's accepting only certain length prefixes. Thx

Regards,

Vikram

[jayaramakrishnan]

Thank you for the update..we have /23 , but we have most of the servers are in one segment, Let me check to change the NAT IP. 

Thanks,

Jayaram