The Complete IS-IS Routing Protocol- P4:IS-IS has always been my favourite Interior Gateway Protocol. Its elegant simplicity, its well-structured data formats, its flexibility and easy extensibility are all appealing – IS-IS epitomizes link-state routing. Whether for this reason or others, IS-IS is the IGP of choice in some of the world’s largest networks. Thus, if one is at all interested in routing, it is well worth the time and effort to learn IS-IS. | Conclusion 77 The above example shows a very simple policy. It creates a policy named all-statics under the policy-options branch of the configuration hierarchy. Next it defines the match and action clauses. If the route s originating protocol is from static then accept that prefix. Note that in the then part no detailed action is actually specified for the prefix. This is largely dependent on which routing protocol has called the policy and where the policy is applied. For example if the policy is applied as an export policy within OSPF protocols ospf export all-statics This means that all prefixes that are installed in the routing table and are static routes these alone match the policy all-statics will be redistributed into OSPF and announced to all OSPF neighbours. But if the same policy is applied as an export policy within BGP protocols bgp group internal export all-statics neighbor neighbor _. This means that all the static routes present in the table are not announced to all OSPF neighbors as in the previous example but only to the BGP peers present in the peer-group internal. So the ultimate result depends on where the policy is applied. Policy processing is typically deployed for filtering BGP routes. Generally IS-IS policies are simple one-to-three term policies which are easily readable. To learn more about the JUNOS routing policy language and policy processing in general the Juniper Networks Book Initiative JNBI lists pointers to good books with more detailed elaboration on about policy processing. Further Documentation The entire documentation about Juniper Networks Routers is available on the Juniper Networks public website at http techpubs . Further documentation and books about JUNOS routing technology is posted at http company jnbi . Conclusion Both JUNOS and IOS offer the network operator powerful user interfaces to provision troubleshoot and change the network .
