© 2005 Cisco Systems, Inc. All rights reserved. BGP v Customer-to-Provider Connectivity with BGP Implementing Customer Connectivity Using Static Routing

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Outline Overview Why Use Static Routing? Characteristics of Static Routing Designing Static Route Propagation in a Service Provider Network BGP Backup with Static Routes Floating Static Routes with BGP Load Sharing with Static Routes Summary

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Why Use Static Routing? Static routing is used for: –Customers with a single connection to the Internet –Customers with multiple connections to the same service provider in environments where link and equipment failure can be detected Dynamic routing with BGP must be used in all other cases.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Characteristics of Static Routing The customer network must announce a default route. –Redistribute default route into customer IGP if the customer is running EIGRP. –Use default-information originate if the customer is running OSPF or RIP. Customer routes should be carried in BGP, not core IGP. –Redistribute static routes into BGP, not IGP. Routes to subnets of the provider address block should not be propagated to other autonomous systems. –Mark redistributed routes with no-export community. –Use static route tags for consistent tagging.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Default route is configured on the customer router Default route is redistributed into the customer network Route for customer address space is configured on provider router Customer route is redistributed into BGP Characteristics of Static Routing (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Designing Static Route Propagation in a Service Provider Network Identify all possible combination of services offered to a customer, including QoS services. Assign a tag to each combination of services. Configure a route-map that matches defined tags and sets BGP communities or other BGP attributes. Redistribute static routes into BGP through a route-map. For each customer, configure a static route toward the customer with the proper tag.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Static Route Propagation Scenario Sample service offering Addressing Provider-assigned address blocks are not propagated to upstream ISPs. Provider-independent address blocks are propagated to upstream ISP. Quality of service Normal customers Gold customers Define static route tags Advertise Customer Route QoS Type Route Tag Community Values NoNormal1000no-export 387:31000 YesNormal :31000 NoGold2000no-export 387:32000 YesGold :32000

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Static Route PropagationConfigure Route-Maps

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Static Route PropagationRedistribution and Customer Routes

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Static Route PropagationStatic Routes on the Provider Edge Router

© 2005 Cisco Systems, Inc. All rights reserved. BGP v BGP Backup with Static Routes

© 2005 Cisco Systems, Inc. All rights reserved. BGP v BGP Backup with Static Routes (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v BGP Backup with Static Routes (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v BGP Backup with Static Routes (Cont.) The BGP table on the service provider backup router contains the floating static route.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Limitations and corrections Floating static routes do not work correctly with BGP. Weight has to be lowered to default value for other BGP routes to be considered. BGP local preference has to be changed for floating static routes redistributed into BGP, to make sure other routes take precedence. Administrative distance cannot be matched with a route-map; additional tags need to be defined for static routes. Floating Static Routes with BGP

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Advertise Customer Route BackupQoS TypeTagCommunity Values Local Preference Normal1000no-export 387: YesNormal1010no-export 387: YesNormal : Yes Normal : Gold2000no-export 387: YesGold2010no-export 387: YesGold : Yes Gold : Sample Static Route Tags with Backup Floating Static Routes with BGP (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v The redistribution route-map needs to be updated on all provider edge routers. Only the first half of the route-map is displayed. Floating Static Routes with BGP (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Load Sharing with Static Routes: Outgoing Traffic Outgoing traffic load sharing is easy to achieve. Each customer router uses the closest customer edge router as the exit point. Balanced load sharing is achieved if the customer edge routers are collocated.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Load Sharing with Static Routes: Return Traffic Load sharing of return traffic is impossible to achieve with multiple edge routers. All provider routers select the same BGP route to the destination. All return traffic arrives at the same provider edge router.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Load Sharing with Static Routes: Optimizing Return Traffic You can optimize return traffic load sharing. Each provider edge router advertises only part of the customer address space into the provider backbone. Every provider edge router also advertises the whole customer address space for backup purposes. Load sharing is not optimalevery link will carry return traffic for part of the customer address space.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Load Sharing with Static Routes: Optimizing Return Traffic (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Summary You can use static routing in most cases when the customer network is connected to a single ISP. If there is a single connection, you should always use static routing, because there is no redundancy. In static routing, the customer network must announce a default route; customer routes should be carried in BGP, not core IGP; and routes to subnets of the provider address block should not be propagated to other autonomous systems. In propagating static routes in a service provider network, identify all different service levels that are offered to customers and then all the combinations of these service levels, assign each combination its own tag value and its own community, configure a route-map, and configure static routes.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v Summary (Cont.) Depending on the origin of the customer address space, the provider may elect not to advertise the customer space, choosing to advertise a larger aggregate route instead. When you are using static routes in a backup scenario, floating static routes are used on the backup routers. After the backup floating static route becomes active, its AD is ignored by BGP because the locally originated route will have a higher weight and be preferred, requiring the use of BGP attributes to ensure proper floating static operation. Load balancing can be achieved for outgoing traffic. Return traffic causes problems when multiple connections exist to more than one provider router.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v