Annoucing ASN for customer

kayzie.cheng · ‎09-09-2013

Hi all,

Good day. I am fairly new to Cisco and I am using a Cisco 10720 router announcing our own ASN and prefixes. Recently, a customer asked if we can announce their ASN and prefix with our router and their server will be hosted at our end. There are a few questions that I wanted to ask:

1. I am already announcing one ASN for our own company use, and I understand that there can only be 1 ASN in 1 router. In that case, will it be possible for me to announce the customer's ASN by prepend it to our ASN?

2. Customer will not put a router of their own in our network, therefore, we will be using our router to announce their prefixes. I understand that we will need to include the prefix in my network. In this scenario, is it still possible for us to announce the prefix under customer's ASN?

Apology if the questions is too brief, as its my first time dealing with transit configuration.

Thank you.

Peter Paluch · ‎09-10-2013

Hi Kayzie,

1. I am already announcing one ASN for our own company use, and I  understand that there can only be 1 ASN in 1 router. In that case, will  it be possible for me to announce the customer's ASN by prepend it to  our ASN?

Yes, that is true. You will be able to do it in the neighbor route-map out command when advertising the customer's route to your eBGP peers. I am not aware of a way to inject a route into your BGP using network or redistribute commands while manipulating its AS_PATH, though - within your own AS, the route will simply be known as an internal route and it will not carry the customer's ASN. Only in the eBGP sessions, the AS_PATH can be prepended to.

2. Customer will not put a router of their own in our network,  therefore, we will be using our router to announce their prefixes. I  understand that we will need to include the prefix in my network. In  this scenario, is it still possible for us to announce the prefix under  customer's ASN?

Within your network, the customer's prefix will have an empty AS_PATH just like any other your internal route. You could possibly configure a community attribute to distinguish this prefix from other prefixes, and on your border routers, set the AS_PATH prepending based on the presence of this attribute.

I am not sure if this answers your question - please feel welcome to ask further.

Best regards,

Peter

kayzie.cheng · ‎09-10-2013

Hi Peter,

That solution sounds good to me. I'll give it a try.

Thank you very much for your help.

Best Regards,

Kayzie