Allied Telesis X8100, x908 BGP Configuring Prefix Filters, awplusconfig-router# do show ip route

Page 25

BGP: Configuring Prefix Filters

5.Check that the IP route table now contains only the other route from the neighbor.

awplus(config-router)# do show ip route

Codes: C - connected, S - static, R - RIP, B - BGP O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2

* - candidate default

C 45.45.45.0/24 is directly connected, vlan1

B52.0.0.0/8 [20/0] via 45.45.45.46, vlan1, 00:26:45

C64.0.0.0/4 is directly connected, vlan64

Use Route Maps and Other Filters to Filter and Alter BGP and OSPF Routes Page 25

Image 25

Contents Technical Guide IntroductionIntroduction ContentsWhich products and software version does it apply to? BGP Applying Route Maps to Imported RoutesWhich products and software version does it apply to? Related How To NotesBGP Concepts and Terminology BGP updatesBGP peers Origin Update attributesAS-path Next-hopBGP Overview of the Available Filter Types Access Control List ACL filtersFilter types Distribute filtersDifference and Relationship in BGP Examples for filtering BGP Update messagesBGP Example Hierarchy of the Different Filters Example Distribute filters on page  Example AS path filters on page  Example Prefix filters on pageBasic configuration AlliedWare switch Confirming the neighbor relationshipawplus#show ip route About ACLs BGP Configuring Distribute FiltersExample Distribute filters Using ACLs as filtersFilter out one particular route from a neighbor Filter out a range of prefix lengths 3. Check that the IP route table now includes all the routes awplusconfig# neighbor 45.45.45.46 distribute-list list2 in6. Shut down the neighbor, and then bring it up again Use a numbered ACL instead of a named ACL 4. Check that the IP route table no longer includes 52.0.0.0/8 AS path lists BGP Configuring AS Path FiltersExample AS path filters Using AS path lists as path filtersDiscard or allow routes from a neighbor a neighbor 4. Shut down the neighbor, and then bring it up again7. Shut down the neighbor, and then bring it up again An outgoing filter that uses an AS-path list Another exampleBGP Configuring AS Path Filters About prefix lists BGP Configuring Prefix Filters Mask length Example Prefix filters Using prefix lists as prefix filtersawplusconfig-router# neighbor neighbor prefix-list list-name in awplusconfig-router# neighbor neighbor prefix-list list-name outFilter out a range of different prefix lengths awplusconfig-router# do show ip route Structure of a route map BGP Configuring Route MapsClauses Configuring a match clauseAn AS path list Case A community listOne or more prefixes, by using an ACL One or more prefixes, by using a prefix listA next hop address Configuring a set clauseAn origin A metric the MED attributeset community community-values additive set atomic-aggregate set weightset extcommunity rtsoo ext-comm-number set ip next-hop ipaddOne match clause with an action The effect of different combinations of clausesNo match clause and one or more set clauses A match clause and one or more set clausesUpdate 1 to Peer Update from PeerUpdate 2 to Peer Router ASFirst, enter BGP router mode for the AS. The prompt should look like Example B Match on a prefix-list that denies an entry Examplesawplusconfig#ip prefix-list test1 permit 52.0.0.0/8 awplusconfig-route-map#set metric4. Apply this route map as the in route map on the neighbor Example E Prepending AS numbers Example D Matching on a next-hop prefix-listawplusconfig-route-map#match ip address awplusconfig-route-map#router bgpThe routes coming from that peer has community 1. Configure the AW peer to send out a community numberadd ip routem=com entry=1 set commmun=8989 set bgp peer=45.45.45.45 outroutemap=com sendcommunity=yesBGP#show ip route set bgp peer=45.45.45.45 outroutemap=mixed sendcommunity=yes 8. Add that ACL as a distribute-list in-filter on the neighbor route-map marker permit Examples Route maps ACLs Path filters Prefix filtersSyntax BGP Applying Route Maps to Imported RoutesOther Uses of Route Maps neighbor default-originateneighbor unsuppress-map networkRoute map configuration BGP configurationBGP Route Map Filtering Example set local-preference route-map outdef permit Metric OSPF Configuring Route Maps for Filtering and Modifying OSPF RoutesInterface A prefix, by using an ACL A prefix, by using a prefix listExternal route type  Set the metric, by using the command set metric OSPF Applying Route Maps

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