Allied Telesis x908 Example D Matching on a next-hop prefix-list, Example E Prepending AS numbers

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Example D Matching on a next-hop prefix-list

Examples

Example D Matching on a next-hop prefix-list

1.Create a prefix-list that matches on the neighbor's IP address:

awplus#ship prefix-list nh-test permit 45.45.45.46/32

2.Create a route map with a permit entry that matches on this prefix-list as a next-hop:awplus#shroute-map nh-test permit 1

awplus#shmatch ip next-hop prefix-list nh-test

3.Apply this route map as the in route map on the neighbor:

awplus(config)#router bgp 34567

awplus(config-router)#neighbor 45.45.45.46 route-map nh-test in

4.Shut down the neighbor, and then bring it up again:

awplus(config-router)#neighbor 45.45.45.46 shutdown awplus(config-router)#neighbor 45.45.45.46 no shutdown

5.All the routes are learnt OK from the neighbor:

awplus#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

B45.0.0.0/8 [20/0] via 45.45.45.46, vlan1, 00:00:03

C45.45.45.0/24 is directly connected, vlan1

B52.0.0.0/8 [20/0] via 45.45.45.46, vlan1, 00:00:03

C64.0.0.0/4 is directly connected, vlan64

Example E Prepending AS numbers

1.Create a route map that prepends a list of AS numbers to the attribute field of outgoing updates:

awplus(config)#route-map as-list-test permit 1

awplus(config-route-map)#match ip address 1

awplus(config-route-map)#set as-path prepend 11 22 33 44 55 66 77 88 99 1010 1111 1212 1313 1414 1515 1616

2.Set this as the out route map for the neighbor 45.45.45.46

awplus(config-route-map)#router bgp 34567

awplus(config-router)#neighbor 45.45.45.46 route-map as-list- test out

3.Shut down the neighbor, and then bring it up again:

awplus(config-router)#neighbor 45.45.45.46 shutdown awplus(config-router)#neighbor 45.45.45.46 no shutdown

4.Now, check the routes learnt on the neighbor - note the long AS-path list:

Manager BGP peer> show bgp route

Page 38 Use Route Maps and Other Filters to Filter and Alter BGP and OSPF Routes

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Contents Introduction Technical GuideWhich products and software version does it apply to? ContentsIntroduction BGP Applying Route Maps to Imported RoutesRelated How To Notes Which products and software version does it apply to?BGP peers BGP updatesBGP Concepts and Terminology AS-path Update attributesOrigin Next-hopFilter types Access Control List ACL filtersBGP Overview of the Available Filter Types Distribute filtersExamples for filtering BGP Update messages Difference and Relationship in BGP Example Distribute filters on page Hierarchy of the Different FiltersBGP Example  Example AS path filters on page  Example Prefix filters on pageBasic configuration awplus#show ip route Confirming the neighbor relationshipAlliedWare switch BGP Configuring Distribute Filters About ACLsFilter out one particular route from a neighbor Using ACLs as filtersExample Distribute filters Filter out a range of prefix lengths 6. Shut down the neighbor, and then bring it up again awplusconfig# neighbor 45.45.45.46 distribute-list list2 in3. Check that the IP route table now includes all the routes Use a numbered ACL instead of a named ACL awplusconfig-router# do show ip route BGP Configuring AS Path Filters AS path listsDiscard or allow routes from a neighbor Using AS path lists as path filtersExample AS path filters 7. Shut down the neighbor, and then bring it up again 4. Shut down the neighbor, and then bring it up againa neighbor Another example An outgoing filter that uses an AS-path listBGP Configuring AS Path Filters Mask length BGP Configuring Prefix FiltersAbout prefix lists awplusconfig-router# neighbor neighbor prefix-list list-name in Using prefix lists as prefix filtersExample Prefix filters awplusconfig-router# neighbor neighbor prefix-list list-name outFilter out a range of different prefix lengths BGP Configuring Prefix Filters BGP Configuring Route Maps Structure of a route mapAn AS path list Configuring a match clauseClauses A community list CaseOne or more prefixes, by using a prefix list One or more prefixes, by using an ACLAn origin Configuring a set clauseA next hop address A metric the MED attributeset community community-values additive set extcommunity rtsoo ext-comm-number set weightset atomic-aggregate set ip next-hop ipaddNo match clause and one or more set clauses The effect of different combinations of clausesOne match clause with an action A match clause and one or more set clausesUpdate 2 to Peer Update from PeerUpdate 1 to Peer Router AS First, enter BGP router mode for the AS. The prompt should look like awplusconfig#ip prefix-list test1 permit 52.0.0.0/8 ExamplesExample B Match on a prefix-list that denies an entry awplusconfig-route-map#set metric4. Apply this route map as the in route map on the neighbor awplusconfig-route-map#match ip address Example D Matching on a next-hop prefix-listExample E Prepending AS numbers awplusconfig-route-map#router bgpadd ip routem=com entry=1 set commmun=8989 1. Configure the AW peer to send out a community numberThe routes coming from that peer has community 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 ACLs Path filters Prefix filters Route mapsBGP Applying Route Maps to Imported Routes Syntaxneighbor unsuppress-map neighbor default-originateOther Uses of Route Maps networkBGP Route Map Filtering Example BGP configurationRoute map configuration set local-preference route-map outdef permit Interface OSPF Configuring Route Maps for Filtering and Modifying OSPF RoutesMetric External route type A prefix, by using a prefix listA prefix, by using an ACL OSPF Applying Route Maps  Set the metric, by using the command set metric

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