
Configuring OSPF Services
4-17
By default, Bay Networks boundary routers that generate ASEs set the external
route tag field to 0. For a boundary router running OSPF and BGP, the network
administrator can configure OSPF to set the external route tag field with a value in
accordance with RFC 1403, “OSPF/BGP Interaction.”
In Figure 4-7, for example, boundary router R14 running OSPF and BGP learns
external routes via BGP:
1. R14 generates an ASE describing the route. OSPF fills in the external route
tag with BGP-specific information according to RFC 1403.
2. R14 injects the ASE into the AS, and OSPF routers flood the ASE throughout
the AS.
3. R1, which runs OSPF and BGP, receives the ASE. R1 generates a BGP
update, using the contents of the external route tag to set the Origin and AS
Path attributes in the update.
Figure 4-7. AS External Route Tag
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