Example: air traffic controller

BGP · P ART 1 - PacketLife.net

Jeremy PART1 TypeAbout BGPeBGP ADiBGP ADPath Vector20200 StandardProtocolsTransportAuthentication RFC 4271 IPTCP/179MD5 Path SelectionAttributeWeightAdministrative preferenceDescription1 PreferenceHighestLocal PreferenceCommunicated between peers within an AS2 HighestSelf-originatedPrefer paths originated locally3 TrueAS PathMinimize AS hops4 ShortestOriginPrefer IGP-learned routes over EGP, and EGP over unknown5 IGPMEDUsed externally to enter an AS6 LowestExternalPrefer eBGP routes over iBGP7eBGPIGP CostConsider IGP metric8 LowesteBGP PeeringFavor more stable routes9 OldestRouter IDTie breaker10 LowestInfluencing Path SelectionWeightneighbor weight 200 MEDdefault-metric 400 Local Preferencebgp default local-preference 100 Route Mapneighbor route-map FooTerminologyAutonomous System (AS)A logical domain under the control of a single entityExternal BGP (eBGP)BGP adjacencies which span autonomous system boundariesInternal BGP (iBGP)BGP adjacencies formed within a single ASSynchronization RequirementA route must be known by an IGP before it may be advertised to BGP peersPacket TypesOpenUpdateKeepaliveNotificationNeig hbor StatesIdle Neighbor is not respondingConnect TCP session establishedOpen Sent Open message sentOpen Confirm Respons

packetlife.net by Jeremy Stretch v2.1-r1 BGP · P ART 1 Type About BGP eBGP AD iBGP AD Path Vector 20 200 Standard Protocols Transport Authentication RFC 4271 IP …

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Transcription of BGP · P ART 1 - PacketLife.net

1 Jeremy PART1 TypeAbout BGPeBGP ADiBGP ADPath Vector20200 StandardProtocolsTransportAuthentication RFC 4271 IPTCP/179MD5 Path SelectionAttributeWeightAdministrative preferenceDescription1 PreferenceHighestLocal PreferenceCommunicated between peers within an AS2 HighestSelf-originatedPrefer paths originated locally3 TrueAS PathMinimize AS hops4 ShortestOriginPrefer IGP-learned routes over EGP, and EGP over unknown5 IGPMEDUsed externally to enter an AS6 LowestExternalPrefer eBGP routes over iBGP7eBGPIGP CostConsider IGP metric8 LowesteBGP PeeringFavor more stable routes9 OldestRouter IDTie breaker10 LowestInfluencing Path SelectionWeightneighbor weight 200 MEDdefault-metric 400 Local Preferencebgp default local-preference 100 Route Mapneighbor route-map FooTerminologyAutonomous System (AS)A logical domain under the control of a single entityExternal BGP (eBGP)BGP adjacencies which span autonomous system boundariesInternal BGP (iBGP)BGP adjacencies formed within a single ASSynchronization RequirementA route must be known by an IGP before it may be advertised to BGP peersPacket TypesOpenUpdateKeepaliveNotificationNeig hbor StatesIdle Neighbor is not respondingConnect TCP session establishedOpen Sent Open message sentOpen Confirm Response receivedEstablished Adjacency establishedTroubleshootingshow ip bgp [summary]show ip bgp neighborsshow ip route [bgp]clear ip bgp * [soft]debug ip bgp [.]

2 ]Active Attempting to connectWell-known Mandatory Must be supported and propagatedWell-known Discretionary Must be supported; propagation optionalOptional Transitive Marked as partial if unsupported by neighborOptional Nontransitive Deleted if unsupported by neighborAttributesAggregator7ID and AS of summarizing routerList of autonomous systems which the advertisement has traversedAS Path2 Atomic Aggregate6 Includes ASes which have been dropped due to route aggregationOriginating cluster13 Cluster IDRoute tag8 CommunityMetric for internal neighbors to reach external destinations (default 100)Local Preference5 Multiple Exit Discriminator (MED)4 Metric for external neighbors to reach the local AS (default 0)External peer in neighboring AS3 Next HopOrigin type (IGP, EGP, or unknown)1 OriginThe originator of a reflected route9 Originator IDWeight--Cisco proprietary, not communicated to peers (default 0)

3 NameDescriptionList of cluster IDs10 Cluster ListIgnoreAS Pathbgp bestpath as-path ignoreIgnore Cost Communitiesbgp bestpath cost-community Jeremy PART2 Configuration Exampleinterface Serial1/0description Backbone to Bip address !interface Serial1/1description Backbone to Cip address !interface FastEthernet2/0description LANip address !router bgp 65100no synchronizationnetwork mask mask South peer-groupneighbor South remote-as 65200neighbor peer-group Southneighbor peer-group Southno 65100AS 65200F0/0F0/0 ABCOSPFF2/0F2/0S1/0S1/0S1/0S1/1F2/0inter face FastEthernet0/0description Backbone to Bip address !interface Serial1/0description Backbone to Aip address !interface FastEthernet2/0description LANip address !router ospf 100network area 0network area 2!router bgp 65200no synchronizationredistribute ospf 100 route-map LAN_Subnetsneighbor remote-as 65200neighbor remote-as 65100no auto-summary!

4 Access-list 10 permit !route-map LAN_Subnets permit 10match ip address 10set metric 100interface FastEthernet0/0description Backbone to Cip address !interface Serial1/0description Backbone to Aip address !interface FastEthernet2/0description LANip address !router ospf 100network area 0network area 1!router bgp 65200no synchronizationredistribute ospf 100 route-map LAN_Subnetsneighbor remote-as 65200neighbor remote-as 65100no auto-summary!access-list 10 permit !route-map LAN_Subnets permit 10match ip address 10set metric 100 Router A Routing TableRouter B Routing is subnetted, 2 subnetsC is directly connected, S1/1C is directly connected, S1/0C is directly connected, F2/0B [20/100] via [20/100] via is subnetted, 2 subnetsB [20/0] via is directly connected, S1 is subnetted, 1 subnetsC is directly connected, F0/0B [20/0] via is directly connected, F2/0O IA [110/2] via , F0/0 Router ARouter CRouter B


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