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User Guide for Cisco Security Manager 4.4
OL-28826-01
64
Configuring Routing Policies
This chapter contains the following topics:
•BGP Routing on Cisco IOS Routers, page 64-1
•BGP Routing Policy Page, page 64-4
•EIGRP Routing on Cisco IOS Routers, page 64-8
•EIGRP Routing Policy Page, page 64-13
•OSPF Routing on Cisco IOS Routers, page 64-19
•OSPF Interface Policy Page, page 64-30
•OSPF Process Policy Page, page 64-34
•RIP Routing on Cisco IOS Routers, page 64-42
•RIP Routing Policy Page, page 64-45
•Static Routing on Cisco IOS Routers, page 64-50
•Static Routing Policy Page, page 64-51

BGP Routing on Cisco IOS Routers

BGP is an Exterior Gateway Protocol (EGP) that guarantees the loop-free exchange of routing
information between autonomous systems (ASs). The primary function of a BGP system is to exchange
information with other BGP systems about the networks it can reach, including AS path information.
This information can be used to construct a graph of AS connectivity from which routing loops can be
pruned and with which AS-level policy decisions can be enforced.
BGP is the routing protocol used on the Internet and is commonly used between Internet service
providers. To achieve scalability at this level, BGP uses several route parameters (attributes) to define
routing policies and maintain a stable routing environment. Additionally, BGP uses classless
interdomain routing (CIDR) to greatly reduce the size of Internet routing tables.
A BGP route consists of a network number, a list of ASs through which information has passed (called
the autonomous system path), and the defined path attributes.
A BGP router exchanges routing information only with those routers that you define as its neighbors.
BGP neighbors exchange complete routing information when the TCP connection between them is
established. Updates are sent to neighbors only when changes to the routing table are detected. BGP
routers do not send regular, periodic updates.
The following topics describe the tasks you perform to create a BGP routing policy: