ShowIPBGP

Most of the decent size of ISP provides BGP community string for their customer. By using BGP community string, you can control our announcement globally and it instantly affects your inbound traffic. In these days, modifying backbone routing policy in ISP is common. They don't want to loose their customer's traffic, so they apply BGP attribute to customer's announcement to avoid those traffic is leaving their backbone.

• BGP Tutorial for ISP customers - Do I need BGP?
• BGP Tutorial for ISP customers - Own ASN or borrowing one.
• BGP Tutorial for ISP customers - Enough memory for full routes?
• BGP Tutorial for ISP customers - Controlling outbound traffic.
• BGP Tutorial for ISP customers - Controlling inbound traffic.
• BGP Tutorial for ISP customers - Configuring BGP.
• BGP Tutorial for ISP customers - BGP community string from ISP.
• BGP Tutorial for ISP customers - Verifying BGP routes.
• BGP Tutorial for ISP customers - BGP Troubleshooting.

To bring BGP session minimum requires a configuration is really simple.  Just three lines of BGP statement will bring BGP session.
This is kinds of important to know, when you are troubleshooting.  If BGP doesnt come up, just simplify BGP configuration. It is sometimes best troubleshooting steps.

• BGP Tutorial for ISP customers - Do I need BGP?
• BGP Tutorial for ISP customers - Own ASN or borrowing one.
• BGP Tutorial for ISP customers - Enough memory for full routes?
• BGP Tutorial for ISP customers - Controlling outbound traffic.
• BGP Tutorial for ISP customers - Controlling inbound traffic.
• BGP Tutorial for ISP customers - Configuring BGP
• BGP Tutorial for ISP customers - BGP community string from ISP.
• BGP Tutorial for ISP customers - Verifying BGP routes.
• BGP Tutorial for ISP customers - BGP Troubleshooting.

Controlling inbound traffic is the most important consideration when you are configuring BGP. If you have more than one ISP links, definetely you need to make sure your BGP announcement is propagate to Internet. If you have only one link to the ISP, again you don't really need BGP. Simple static route statement should be taking care of your needs.
Redundancy, failover and load-balancing traffic those are few major reasons that you have multiple links to ISP. Your BGP announcement is directly affecting your inbound traffic. Yes, it kinds of confuse if you are not dealing with BGP daily basis. How you annouce your routes bring traffic on one of your uplinks.

• BGP Tutorial for ISP customers - Do I need BGP?
• BGP Tutorial for ISP customers - Own ASN or borrowing one.
• BGP Tutorial for ISP customers - Enough memory for full routes?
• BGP Tutorial for ISP customers - Controlling outbound traffic.
• BGP Tutorial for ISP customers - Controlling inbound traffic.
• BGP Tutorial for ISP customers - Configuring BGP.
• BGP Tutorial for ISP customers - BGP community string from ISP.
• BGP Tutorial for ISP customers - Verifying BGP routes.
• BGP Tutorial for ISP customers - BGP Troubleshooting.

Outbound traffic control is actually easier than you thought. If you have single ISP link, all outbound traffic will obviously exit out the link. As I mentioned earlier, if you have single ISP link then you don't really need BGP. Probably you may have more questions, if you have more than two ISP links. Redundanacy and load-sharing would be biggest concerns.

• BGP Tutorial for ISP customers - Do I need BGP?
• BGP Tutorial for ISP customers - Own ASN or borrowing one.
• BGP Tutorial for ISP customers - Enough memory for full routes?
• BGP Tutorial for ISP customers - Controlling outbound traffic.
• BGP Tutorial for ISP customers - Controlling inbound traffic.
• BGP Tutorial for ISP customers - Configuring BGP.
• BGP Tutorial for ISP customers - BGP community string from ISP.
• BGP Tutorial for ISP customers - Verifying BGP routes.
• BGP Tutorial for ISP customers - BGP Troubleshooting.