Figure 4: Routing Without CIDR
With CIDR, the ISP can aggregate the routes as 192.168.128.0/17 and advertise a
single address to that prefix, as shown in Figure 5 on page 10.
Figure 5: Routing with CIDR
Path Attributes
A path attribute provides some additional information about a route. If a BGP speaker
has more than one route to the same destination prefix, it selects one of those routes
to use (the “ best” route) based on the path attributes. BGP as implemented on the
Juniper Networks E Series Broadband Services Router specifies detailed and complex
criteria for picking the best route; this helps ensure that all routers will converge to
the same routing table, a necessary behavior to avoid routing loops. See “Selecting
the Best Path” on page 106 for more information.
10 ■ Overview
JUNOSe 11.1.x BGP and MPLS Configuration Guide
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