BGP & Peering Hands-On: Part I

Transcription

1 THE PERFORMANCE NETWORK AND ENGINEERS YOU CAN RELY ON. BGP & Peering Hands-On: Part I

2 Introduction Presentation has some configuration examples. DISCLAIMER & LIMITATION OF LIABILITY: We re not liable for anything that breaks if you use these examples. Always do your homework, don t try this at home, and don t mess with your network outside of a maintenance window ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. WE RE NOT LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF USE, DATA, OR PROFITS; DOWNTIME, OUTAGE OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF ANY EXAMPLES OR INFORMATION IN THIS PRESENTATION, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Uses Cisco CLI We ll make Juniper CLI too, if people are interested. Aimed at Service Providers and Enterprises Feel free to ask questions

3 BGP & Peering Hands-On: Part I Definitions Transit BGP Configuration Example Peering BGP Configuration Example Connecting to an Internet Exchange

4 THE PERFORMANCE NETWORK AND ENGINEERS YOU CAN RELY ON. Definitions

5 Transit Most people confuse peering with transit. They will typically tell you we peer with ISP X using BGP. IP Transit is the service of allowing your network traffic to cross or transit through an intermediate network to reach the larger Internet. When you pay someone (let s say ISP X) to connect you to the internet, you are buying Transit. It doesn t matter if you peer with them using BGP you are still buying transit, and ISP X is your Transit, not a Peer.

6 Transit

7 Transit

8 Transit

9 Peering Peering is a voluntary interconnection of administratively separate Internet networks (Autonomous Systems) for the purpose of exchanging traffic between the customers (or end-users) of each network. You advertise only your own IP blocks and/or your customer routes to your peer, and they do the same to you. A peer network does not give you connectivity to the larger Internet (that would be called transit ). You only reach their network and/or their customer networks and vice versa. Peering is typically settlement-free, meaning neither parties pay each other for the cost of exchanging traffic. If there are costs incurred due to the exchanging of traffic, such costs are typically shared by both parties ( cost neutral ). Also referred to as Settlement-Free Interconnection (SFI) Agreement

10 Peering

11 Peering

12 Peering

13 THE PERFORMANCE NETWORK AND ENGINEERS YOU CAN RELY ON. BGP Configuration Examples

14 Example Scenario Our imaginary network is called Acme Corporation with AS We take Transit from Level(3), whose AS is We also Peer with TowardEX, whose AS is Our IP block is /24.

15 Transit BGP Configuration to Level3 router bgp no synchronization no auto-summary bgp deterministic-med network mask neighbor remote-as 3356 neighbor description Level3 Transit Gi1/1 neighbor prefix-list Our-Networks out ip prefix-list Our-Networks seq 10 permit /24 ip prefix-list Our-Networks seq 255 deny /0 le 32 ip route Null0 254

16 Peer BGP Configuration to TowardEX router bgp network mask neighbor remote-as 3356 neighbor description Level3 Transit Gi1/1 neighbor prefix-list Our-Networks out neighbor route-map policy-transit-inbound in neighbor remote-as neighbor description TWDX Boston IX neighbor prefix-list Our-Networks out neighbor route-map policy-peer-inbound in ip prefix-list Our-Networks seq 10 permit /24 ip prefix-list Our-Networks seq 255 deny /0 le 32 ip route Null ( more ) continued to next page --

17 Peer BGP Configuration to TowardEX (Continued) route-map policy-transit-inbound permit 5 set local-preference 70 route-map policy-peer-inbound permit 5 set local-preference 80

18 Peer BGP Configuration to TowardEX (Continued) route-map policy-transit-inbound permit 5 set local-preference 70 route-map policy-peer-inbound permit 5 set local-preference 80 Remember the BGP Best-Path Selection Process: 1. Largest Weight (Cisco proprietary; CAUTION: FOR USE BY BROKEN NETWORKS ONLY) 2. Highest Local Preference 3. Shortest AS_PATH 4. Lowest Origin Type (IGP (i) < EGP (e) < Incomplete (?) 5. Lowest MED (MULTI_EXIT_DISC) 6. ebgp over ibgp 7. Lowest IGP Cost/Metric to Next-Hop

19 Peer BGP Configuration to TowardEX (Continued) route-map policy-transit-inbound permit 5 set local-preference 70 route-map policy-peer-inbound permit 5 set local-preference 80 Highest Local Preference o o Above, our peer learned route is set to 80, transit learned route is set to 70. So we always prefer peering routes over transit routes (to save cost, etc). Your internally originated or your customer routes should always have higher local preference than anyone else (i.e. 100 in our example). Ever wondered why your upstream transit provider still sends you quite a bit of traffic when you prepend your AS_PATH in a really obnoxious manner? i and yet Level3 (3356) still sends you traffic..

20 Peer BGP Configuration to TowardEX (Continued) route-map policy-transit-inbound permit 5 set local-preference 70 route-map policy-peer-inbound permit 5 set local-preference 80 Highest Local Preference o o Above, our peer learned route is set to 80, transit learned route is set to 70. So we always prefer peering routes over transit routes (to save cost, etc). Your internally originated or your customer routes should always have higher local preference than anyone else (i.e. 100 in our example). Ever wondered why your upstream transit provider still sends you quite a bit of traffic when you prepend your AS_PATH in a really obnoxious manner? Please don t prepend your AS gazillion times. It will not help you other than making you look completely stupid on live television. 1 to 3 times is enough.

21 THE PERFORMANCE NETWORK AND ENGINEERS YOU CAN RELY ON. Connecting to an Internet Exchange

22 Welcome to the Boston Internet Exchange

23 Step 1. Prepare Your IX Interface interface GigabitEthernet1/1 description MarkleyIX Boston IDC.BO1.RR02.24.psf01.bo1.xe-1/0/7 ip address ipv6 address 2001:504:24:1::6417:1/64 no ip redirects no cdp enable ip ospf cost 5 router ospf 100 passive-interface GigabitEthernet1/1 TURN OFF: CDP, IGMP/PIM, DECnet, AppleTalk, etc DO NOT ENABLE Interior Gateway Protocols (IGP) such as OSPF, IS-IS, RIP, EIGRP, etc on the IX Interface For example, if using OSPF or IS-IS, use passive-interface IX_interface_name

24 Step 2. Register on PeeringDB Visit and register an account with your company s AS number. It is free to join We are listed as Boston Internet Exchange in the list of exchange points on PeeringDB. Find us and add to your Peering Record Your network s peering record can be quickly viewed by going to AS NUMBER>.peeringdb.com. For example: etc..

25 Step 3. Start Peering Contact the other networks you want to peer with (typically by ) and get their consent to peer with you. Then go ahead and configure the BGP session for each agreed peer: router bgp network mask neighbor BostonIX peer-group neighbor BostonIX prefix-list Our-Networks out neighbor BostonIX route-map policy-peer-inbound in neighbor remote-as neighbor description TWDX Boston IX neighbor peer-group BostonIX neighbor remote-as neighbor description Boston IX neighbor peer-group BostonIX neighbor remote-as 3856 neighbor description Boston IX neighbor peer-group BostonIX

26 End of Tutorial THE PERFORMANCE NETWORK AND ENGINEERS YOU CAN RELY ON.