BGP config for enterprise networks

[ajay kondapalli]

When we take MPLS, We can use BGP as our EGP. We need to coordinate with our ISP to get our BGP config done. (for peer relationships).

At that time , what kind of values are given by ISP to configure on our routers so that he can differentiate our traffic with other customers.

Does ISP give any tag values to us to insert into our route updates using routemaps. ?  What is meant by BGP routing policies ?

In large orgnazations , VoIP is implemented , then do they advertise phone's IP range to ISP so that ISP can route that packets to branch offices of customer?  How do they route data packets, voice and video packets ? 

If there is  video or audio conference going on for multiple locations,  will it be done by Multicasing ? if so how does ISP handle that and route to all branch offices? 

Thanks,

Ajay

[Eehab Suliman]

The ISP will not confuse your traffic with other routers since you have unique routes but you will need to discuss certain values known as bgp attributes.

The attributes are exactly the tag values you mentioned and yes route maps are used extensively to apply the arributes and enforce the policies you have with you IPS. Depending on your relationship with the ISP and what kind of policies you would like to apply these attributes will change. I will attept to explain some common scenarious:

- customer A has 2 links to IPS1. Customers will advertise all his routes to the ISP on link1 with a MED attribute of 50 and will advertise all the routes again to the ISP on link2 with a MED attribute of 100. This will tell the ISP that you are assigning a lower MED of 50 indicating you would like to recieve traffic on link1 and ONLY IF link one is down the ISP should send you traffic on link2.

- Further more you can advertise half you routes to the ISP on link1 with a 50 value and the other half on link2 with a 50 value as well. Letting your ISP know that you want some traffic to come to you on link1 while other routes to arrive on link2. For more information on med search for multi-exit-discriminator

- An ISP can also influence traffic to you via different attributes knowns as local preference and community. ISP will ask you to send your prefered routes with COMMUNITY1 and your less preferred routes with COMMUNITY2. Once you advertise your routes to the ISP the ISP routers will mark your COMMUNITY1
routes with a local preference value of 100 since they are preffered and your COMMUNITY2 routes with a local preference value 50 since they are less favored.
Then your ISP will send traffic on the link with the higher local preference.

- using COMMUNITIES AND LOCAL PREFERENCES you can slipt your incoming traffic (your routes) and recieve traffic in two different links but assign different communities and local preferences in different links.

It all starts with understanding the relationship with you ISP. Please dicsuss this with your ISP and find out exactly what kind of policies they want to apply,
, what attributes they want you to use, how many links are they selling you, etc...then i can probably help you further with the policy application once we are clear on it.

Please remember to rate the answers you find helpful

[Eehab Suliman]

test message

[Mohamed Sobair]

Ajay,

Normall the service Providers set a TAG value to customer prefixes to differenciate between different customer prefixes although it would already be differenciated in the MPLS Network by the RD value, but the practise is to set TAGs on the prefixes.

The Tagging also help to apply common BGP routing Policies to certain sites for certain requirment, the routing policy is simply where you want to apply where your traffic to be routed , applying certain communities whether standard or extended to your prefixes, Blackholing some times if there is suspecious attacks , and etc.

The Voice Packets are simply (Voice Payload or Voice Signaling) both uses The Transport layer Over Internet Layer, so its normally forwarded.

Keep in mind that certain Service Providers block Voice Payloads , it depends on the Provider Policy.

The Video and Audio Conferencing is handledby Multicasting, in this case where you want to have multicast between branches, the service providers has to particpate with the customer in the Multicast routing and TRANSPARENTLY forward your Multicast streams between your CEs.

HTH

Mohamed