Information Technology Reference
In-Depth Information
Figure 9-4
Next-Hop Attribute for Customer Prefixes
BGP Advertisements
10.2.0.0/16
10.3.0.0/16
10.1.1.2/30
10.1.1.1/30
AS 200
AS 100
AS 100
BGP Next Hops
10.2.0.0/16 NH: 10.1.1.1
10.3.0.0/16 NH: 10.1.1.1
The network edge is where the vast majority of BGP policy is applied. The aggregation and
core layers operate on the policy that is defined at the edge when performing best-path
selection. Example 9-3 shows a sample network edge BGP configuration template.
BGP Edge Router Configuration Template
Example 9-3
router bgp <ISP ASN>
no auto-summary
no synchronization
bgp dampening
bgp log-neighbor-changes
bgp router-id <ROUTER ID>
!
neighbor AGG_UPLINK peer-group
neighbor AGG_UPLINK description iBGP Session to Aggregation Routers
neighbor AGG_UPLINK version 4
neighbor AGG_UPLINK password <iBGP Password>
neighbor AGG_UPLINK update-source loopback0
neighbor AGG_UPLINK next-hop-self
neighbor AGG_UPLINK remote-as <ISP ASN>
!
neighbor CUST_GEN_ASN peer-group
neighbor CUST_GEN_ASN description Customers using Generic ASN
neighbor CUST_GEN_ASN version 4
neighbor CUST_GEN_ASN password <Customer Password>
neighbor CUST_GEN_ASN remote-as <Generic ASN>
neighbor CUST_GEN_ASN remove-private-as
neighbor CUST_GEN_ASN default-information originate
!
neighbor CUST_PRIV_ASN peer-group
neighbor CUST_PRIV_ASN description Customer using Private ASN
neighbor CUST_PRIV_ASN version 4
neighbor CUST_PRIV_ASN password <Customer Password>
continues
