© 2001, Cisco Systems, Inc. Multiprotocol BGP
© 2001, Cisco Systems, Inc. Multiprotocol BGP-2 Objectives Upon completion of this chapter, you will be able to perform the following tasks: Explain the difference between BGP for unicast IP and MP-BGP for other protocols Describe how routing information for other protocols is carried in MP-BGP updates Describe the detailed operation of the route refresh mechanism Describe outbound route filters
Standard BGP vs. Multiprotocol-BGP © 2001, Cisco Systems, Inc. Multiprotocol BGP-3
© 2001, Cisco Systems, Inc. Multiprotocol BGP-4 Objectives Upon completion of this section, you will be able to perform the following tasks: Describe the format of standard and multi-protocol BGP routing updates Explain the purpose of address families Describe the BGP capabilities negotiation Configure BGP address families on Cisco IOS devices Configure and monitor BGP capabilities negotiation on Cisco IOS devices
© 2001, Cisco Systems, Inc. Multiprotocol BGP-5 Overview of Standard BGPv4 IP-only routing protocol Used mainly to exchange routing information between autonomous systems Simple BGP Update: Marker Origin AS Path Next-hop Address... NLRI Attributes Prefix
© 2001, Cisco Systems, Inc. Multiprotocol BGP-6 Address Families Address Family is a network layer protocol identifier This parameter is used to differentiate routing updates of different protocols carried across the same BGP session It is a 16-bit value MP-BGP uses an additional sub-address family parameter (8 bits) Usual notation AFI/SAFI (i.e. 1/1)
© 2001, Cisco Systems, Inc. Multiprotocol BGP-7 Address Family Values Address family values currently used with MPBGP: 1/1IP version 4 unicast 1/2 IP version 4 multicast 1/128VPN_IP version 4 unicast All these protocols are essentially IPv4, but they have to be treated separately because of their differences They are regarded as three different protocols by routers
© 2001, Cisco Systems, Inc. Multiprotocol BGP-8 Multiprotocol BGP Updates Designed to carry routing information of any layer-3 protocol Mostly used internally and not just between autonomous systems Multiprotocol BGP update: Marker Origin AS Path Next-hop Address NLRI IPv4 Prefix MP_REACH NLRI MP_UNREACH NLRI Reachable prefixes of other protocols Unreachable prefixes of other protocols Next-hop Address for IPv4 Prefixes
© 2001, Cisco Systems, Inc. Multiprotocol BGP-9 MP_REACH_NLRI Optional non-transitive attribute Type code 14 Contains: –AFI/SAFI to identify the protocol –Next-hop information –Network Layer Reachability Information (NLRI or prefix) NLRI format depends on the protocol (AFI/SAFI)
© 2001, Cisco Systems, Inc. Multiprotocol BGP-10 MP_UNREACH_NLRI Optional non-transitive attribute Type code 15 Contains: –AFI/SAFI to identify the protocol –Withdrawn routes
© 2001, Cisco Systems, Inc. Multiprotocol BGP-11 Capabilities Negotiation BGP version 4 session starts with an exchange of OPEN messages An OPEN message contains: –BGP version –AS number –Hold time –Router identifier –Optional parameter (void by default) Multiprotocol extensions are negotiated as part of OPEN messages Optional parameter with type code 2 is used for negotiation of capabilities Capabilities are identified by an 8-bit Capability Code (CC) field
© 2001, Cisco Systems, Inc. Multiprotocol BGP-12 Capability Codes Capability Code is an 8-bit field CC values are assigned by IANA, values 128255 are vendor specific Some capabilities currently supported by different Cisco IOS versions: –IPv4 unicast (CC=1, AFI=1/1) –IPv4 multicast (CC=1, AFI=1/2) –VPNv4 (CC=1, AFI=1/128) –Standard route refresh (CC=2) –Old style (Cisco proprietary) route refresh (CC=128) –Outbound route filtering (CC=129)
© 2001, Cisco Systems, Inc. Multiprotocol BGP-13 BGP Session Startup Example OPEN: BGPv4, AS=1, HT=180, OP=2: CC=1 AFI=1/1 (IPv4 unicast) CC=128 (old style route-refresh) CC=129 (outbound route filter) OPEN: BGPv4, AS=2, HT=30, OP=2: CC=1 AFI=1/1 (IPv4 unicast) CC=1 AFI=1/2 (IPv4 multicast) CC=1 AFI=1/128 (VPNv4) CC=2 (new style route-refresh) CC=128 (old style route-refresh) AS 1 IOS 12.0(14)S AS 2 IOS 12.1(5)T Unknown capabilities are ignored
© 2001, Cisco Systems, Inc. Multiprotocol BGP-14 Example Summary The two routers exchange a different set of capabilities Only those capabilities supported by both routers are actually used The session may be terminated if one of the routers does not understand the Capabilities optional parameter
© 2001, Cisco Systems, Inc. Multiprotocol BGP-15 Configuring Address Families address-family ipv4 {unicast | multicast} router(config-router)# This command enters the configuration mode for IPv4 unicast or multicast address family address-family vpnv4 router(config-router)# This command enters VPNv4 address family configuration mode
© 2001, Cisco Systems, Inc. Multiprotocol BGP-16 Configuring Address Families (cont.) neighbor neighbor activate router(config-router-af)# Enables the negotiation of capability for configured address family Only IPv4 unicast address familiy is activated by default All other address families are deactivated by default and need to be activated using this command
© 2001, Cisco Systems, Inc. Multiprotocol BGP-17 Disabling Capabilities Negotiation neighbor neighbor dont-capability-negotiate router(config-router)# Routers that support capabilities negotiation will automatically use this optional parameter Depending on BGP implementation of the neighboring router, it may be impossible to establish a BGP session Use this command to disable capability negotiation
© 2001, Cisco Systems, Inc. Multiprotocol BGP-18 Behavior of MP-BGP Multiple BGP sessions are multiplexed onto one TCP session Configuration of MP-BGP for different address families is almost completely separate Global commands that define the BGP session apply to all address families and are configured in the global BGP configuration mode: –“neighbor ip remote-as as” –“neighbor ip update-source intf” –“neighbor ip ebgp-multihop” –“neighbor ip password password” –“neighbor ip timers keepalive holdtime” –“neighbor ip version version” Other commands that only affect updates are configured in the address family configuration mode
© 2001, Cisco Systems, Inc. Multiprotocol BGP-19 Configuration Example AS 1AS 2 router bgp 2 network neighbor remote-as 1 neighbor update-source loopback 0 neighbor next-hop-self neighbor send-community neighbor ebgp-multihop ! address-family vpnv4 neighbor activate neighbor next-hop-self neighbor send-community extended exit-address-family ! If next-hop-self is desired for both IPv4 and VPNv4 it should be entered in the global BGP configuration mode as well as VPNv4 address family configuration mode Remote AS is 1 for both IPv4 and VPNv4 updates. This command can only be entered in global BGP configuration mode.
© 2001, Cisco Systems, Inc. Multiprotocol BGP-20 Monitoring MP-BGP show ip bgp neighbor [neighbor] router# Shows detailed information about BGP neighbors Router#show ip bgp neighbor BGP neighbor is , remote AS 1, external link BGP version 4, remote router ID BGP state = Established, up for 01:48:35 Last read 00:00:28, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received(old) Address family IPv4 Unicast: advertised and received Address family VPNv4 Unicast: advertised Address family IPv4 Multicast: advertised Received 1388 messages, 0 notifications, 0 in queue Sent 1370 messages, 0 notifications, 0 in queue Route refresh request: received 0, sent 1 Default minimum time between advertisement runs is 30 seconds --More-- Router#show ip bgp neighbor BGP neighbor is , remote AS 1, external link BGP version 4, remote router ID BGP state = Established, up for 01:48:35 Last read 00:00:28, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received(old) Address family IPv4 Unicast: advertised and received Address family VPNv4 Unicast: advertised Address family IPv4 Multicast: advertised Received 1388 messages, 0 notifications, 0 in queue Sent 1370 messages, 0 notifications, 0 in queue Route refresh request: received 0, sent 1 Default minimum time between advertisement runs is 30 seconds --More--
© 2001, Cisco Systems, Inc. Multiprotocol BGP-21 Monitoring MP-BGP (cont.) For address family: IPv4 Unicast BGP table version 84, neighbor version 84 Index 1, Offset 0, Mask 0x2 7 accepted prefixes consume 252 bytes Prefix advertised 0, suppressed 0, withdrawn 0 For address family: VPNv4 Unicast BGP table version 1, neighbor version 0 Index 1, Offset 0, Mask 0x2 Inbound soft reconfiguration allowed Private AS number removed from updates to this neighbor NEXT_HOP is always this router 0 accepted prefixes consume 0 bytes Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 20 Threshold for warning message 75% Minimum time between advertisement runs is 3 seconds For address family: IPv4 Multicast BGP table version 1, neighbor version 0 Index 1, Offset 0, Mask 0x2 0 accepted prefixes consume 0 bytes Prefix advertised 0, suppressed 0, withdrawn 0... For address family: IPv4 Unicast BGP table version 84, neighbor version 84 Index 1, Offset 0, Mask 0x2 7 accepted prefixes consume 252 bytes Prefix advertised 0, suppressed 0, withdrawn 0 For address family: VPNv4 Unicast BGP table version 1, neighbor version 0 Index 1, Offset 0, Mask 0x2 Inbound soft reconfiguration allowed Private AS number removed from updates to this neighbor NEXT_HOP is always this router 0 accepted prefixes consume 0 bytes Prefix advertised 0, suppressed 0, withdrawn 0, maximum limit 20 Threshold for warning message 75% Minimum time between advertisement runs is 3 seconds For address family: IPv4 Multicast BGP table version 1, neighbor version 0 Index 1, Offset 0, Mask 0x2 0 accepted prefixes consume 0 bytes Prefix advertised 0, suppressed 0, withdrawn 0...
© 2001, Cisco Systems, Inc. Multiprotocol BGP-22 Troubleshooting MP-BGP debug ip bgp [events] router# Shows detailed information about BGP session negotiation and other events Router#debug ip bgp BGP: went from Idle to Active BGP: open active, delay 27434ms BGP: passive open BGP: went from Active to Idle BGP: went from Idle to Connect BGP: rcv message type 1, length (excl. header) 38 BGP: rcv OPEN, version 4 BGP: went from Connect to OpenSent BGP: sending OPEN, version 4, my as: 3 BGP: rcv OPEN w/ OPTION parameter len: 28 BGP: rcvd OPEN w/ optional parameter type 2 (Capability) len 6 BGP: OPEN has CAPABILITY code: 1, length 4 BGP: OPEN has MP_EXT CAP for afi/safi: 1/1... Router#debug ip bgp BGP: went from Idle to Active BGP: open active, delay 27434ms BGP: passive open BGP: went from Active to Idle BGP: went from Idle to Connect BGP: rcv message type 1, length (excl. header) 38 BGP: rcv OPEN, version 4 BGP: went from Connect to OpenSent BGP: sending OPEN, version 4, my as: 3 BGP: rcv OPEN w/ OPTION parameter len: 28 BGP: rcvd OPEN w/ optional parameter type 2 (Capability) len 6 BGP: OPEN has CAPABILITY code: 1, length 4 BGP: OPEN has MP_EXT CAP for afi/safi: 1/1... IPv4 unicast
© 2001, Cisco Systems, Inc. Multiprotocol BGP-23 Troubleshooting MP-BGP (cont.) BGP: rcvd OPEN w/ optional parameter type 2 (Capability) len 6 BGP: OPEN has CAPABILITY code: 1, length 4 BGP: OPEN has MP_EXT CAP for afi/safi: 1/128 BGP: rcvd OPEN w/ optional parameter type 2 (Capability) len 6 BGP: OPEN has CAPABILITY code: 1, length 4 BGP: OPEN has MP_EXT CAP for afi/safi: 1/2 BGP: rcvd OPEN w/ optional parameter type 2 (Capability) len 2 BGP: OPEN has CAPABILITY code: 128, length 0 BGP: OPEN has ROUTE-REFRESH capability(old) for all address-families BGP: went from OpenSent to OpenConfirm BGP: send message type 1, length (incl. header) 61 BGP: send message type 4, length (incl. header) 19 BGP: rcv message type 4, length (excl. header) 0 BGP: went from OpenConfirm to Established %BGP-5-ADJCHANGE: neighbor Up BGP: send message type 4, length (incl. header) 19 BGP: rcv message type 4, length (excl. header) 0 BGP: send message type 4, length (incl. header) 19 BGP: rcv message type 4, length (excl. header) 0... BGP: rcvd OPEN w/ optional parameter type 2 (Capability) len 6 BGP: OPEN has CAPABILITY code: 1, length 4 BGP: OPEN has MP_EXT CAP for afi/safi: 1/128 BGP: rcvd OPEN w/ optional parameter type 2 (Capability) len 6 BGP: OPEN has CAPABILITY code: 1, length 4 BGP: OPEN has MP_EXT CAP for afi/safi: 1/2 BGP: rcvd OPEN w/ optional parameter type 2 (Capability) len 2 BGP: OPEN has CAPABILITY code: 128, length 0 BGP: OPEN has ROUTE-REFRESH capability(old) for all address-families BGP: went from OpenSent to OpenConfirm BGP: send message type 1, length (incl. header) 61 BGP: send message type 4, length (incl. header) 19 BGP: rcv message type 4, length (excl. header) 0 BGP: went from OpenConfirm to Established %BGP-5-ADJCHANGE: neighbor Up BGP: send message type 4, length (incl. header) 19 BGP: rcv message type 4, length (excl. header) 0 BGP: send message type 4, length (incl. header) 19 BGP: rcv message type 4, length (excl. header) 0... VPNv4 unicast IPv4 multicast Cisco proprietary route refresh
© 2001, Cisco Systems, Inc. Multiprotocol BGP-24 Summary After completing this section, you should be able to perform the following tasks: Describe the format of standard and multi-protocol BGP routing updates Explain the purpose of address families Describe the BGP capabilities negotiation Configure BGP address families on Cisco IOS devices Configure and monitor BGP capabilities negotiation on Cisco IOS devices
© 2001, Cisco Systems, Inc. Multiprotocol BGP-25 Review Questions What is an address family? What is its purpose? What are the differences between standard BGPv4 updates and multiprotocol updates? What are capabilities? What happens if two neighbors have mismatched capabilities? What can happen if one of the routers does not understand the optional parameter for capability negotiation?
Route Refresh © 2001, Cisco Systems, Inc. Multiprotocol BGP-26
© 2001, Cisco Systems, Inc. Multiprotocol BGP-27 Objectives Upon completion of this section, you will be able to perform the following tasks: Identify the benefits of BGP route refresh extension Monitor BGP route refresh operation on Cisco IOS Use route refresh capability to force neighbors to resend routing information
© 2001, Cisco Systems, Inc. Multiprotocol BGP-28 Route Refresh Route Refresh is a new BGP capability It is used to request a neighbor to resend routing information It is typically used after configuration changes to update the BGP table (route map, distribute list, prefix list, filter list, weight, local preference, MED, and so on) Traditional way of accomplishing this is to clear the BGP session
© 2001, Cisco Systems, Inc. Multiprotocol BGP-29 Route Refresh Options Hard Clear Using “clear ip bgp neighbor neighbor” causes a session to close and reestablish There is a down-time of approximately a minute, because it takes time to re-establish the session and to receive new updates After a few “clears”, an upstream ISP may dampen the propagated prefixes for a long time because of route-flap dampening
© 2001, Cisco Systems, Inc. Multiprotocol BGP-30 Route Refresh Options Soft Clear Another option is to use an additional BGP table for each neighbor All received updates are stored in this table This solution may require a lot more memory in ISP’s routers that carry full Internet routing (around 100,000 networks at the time of writing)
© 2001, Cisco Systems, Inc. Multiprotocol BGP-31 Soft-reconfiguration and Memory Utilization BGP Table (ISP3) BGP Table (ISP2) BGP Table (ISP1) BGP table Routing table FIB table ISP1ISP2ISP3 ISP1: networks ISP2: networks ISP3: networks BGP table: paths RT: networks FIB table: networks Sum: networks
© 2001, Cisco Systems, Inc. Multiprotocol BGP-32 Route Refresh Capability Does not require the BGP session to close Does not require any additional memory No down-time Two versions: –Cisco proprietary (Capability Code 128; for all protocols) –Standard (RFC 2918; Capability Code 2; peraddress-family refresh)
© 2001, Cisco Systems, Inc. Multiprotocol BGP-33 Route Refresh Specification Route refresh is a new BGP message with type code 5 It contains two parameters: –Address Family Information –Sub-address Family Information Neighbor will only resend routing information for specified address family It can only be used if the peer has previously advertised capabilities for Route Refresh and multiprotocol extensions for the requested Address Family
© 2001, Cisco Systems, Inc. Multiprotocol BGP-34 Using Route Refresh clear ip bgp { * | neighbor neighbor} in router(config)# Sends a route-refresh message to the neighbor(s) The command only works if the neighbor has previously advertised the Route Refresh capability
© 2001, Cisco Systems, Inc. Multiprotocol BGP-35 Monitoring Route Refresh Functionality show ip bgp neighbor neighbor router# Verify the support for route refresh capability Router#show ip bgp neighbor BGP neighbor is , remote AS 2, external link Index 2, Offset 0, Mask 0x4 BGP version 4, remote router ID BGP state = Established, table version = 51, up for 22:12:51 Last read 00:00:00, last send 00:00:00 Hold time 3, keepalive interval 1 seconds Configured hold time is 3, keepalive interval is 1 seconds Neighbor NLRI negotiation: Configured for unicast routes only Peer negotiated unicast routes only Exchanging unicast routes only Received route refresh capability(new) from peer... Router#show ip bgp neighbor BGP neighbor is , remote AS 2, external link Index 2, Offset 0, Mask 0x4 BGP version 4, remote router ID BGP state = Established, table version = 51, up for 22:12:51 Last read 00:00:00, last send 00:00:00 Hold time 3, keepalive interval 1 seconds Configured hold time is 3, keepalive interval is 1 seconds Neighbor NLRI negotiation: Configured for unicast routes only Peer negotiated unicast routes only Exchanging unicast routes only Received route refresh capability(new) from peer...
© 2001, Cisco Systems, Inc. Multiprotocol BGP-36 Troubleshooting Route Refresh Router#debug ip bgp 23:54:18: BGP: open active, local address :54:18: BGP: sending OPEN, version 4 23:54:18: BGP: OPEN rcvd, version 4 23:54:18: BGP: rcv OPEN w/ OPTION parameter len: 26 23:54:18: BGP: rcv OPEN w/ option parameter type 2 (Capability) len 6 23:54:18: BGP: OPEN has CAPABILITY code: 1, length 4 23:54:18: BGP: OPEN has MP_EXT CAP for afi/safi: 1/1 23:54:18: BGP: rcv OPEN w/ option parameter type 2 (Capability) len 2 23:54:18: BGP: OPEN has CAPABILITY code: 128, length 0 23:54:18: BGP: rcv OPEN w/ option parameter type 2 (Capability) len 2 23:54:18: BGP: OPEN has CAPABILITY code: 2, length 0 23:54:18: BGP: rcv OPEN w/ option parameter type 2 (Capability) len 8 23:54:18: BGP: OPEN has CAPABILITY code: 129, length 6 23:54:18: BGP: rcv REFRESH_REQ for afi/sfai: 1/1 23:54:18: BGP: start outbound soft reconfig for afi/safi: 1/1 Router#debug ip bgp 23:54:18: BGP: open active, local address :54:18: BGP: sending OPEN, version 4 23:54:18: BGP: OPEN rcvd, version 4 23:54:18: BGP: rcv OPEN w/ OPTION parameter len: 26 23:54:18: BGP: rcv OPEN w/ option parameter type 2 (Capability) len 6 23:54:18: BGP: OPEN has CAPABILITY code: 1, length 4 23:54:18: BGP: OPEN has MP_EXT CAP for afi/safi: 1/1 23:54:18: BGP: rcv OPEN w/ option parameter type 2 (Capability) len 2 23:54:18: BGP: OPEN has CAPABILITY code: 128, length 0 23:54:18: BGP: rcv OPEN w/ option parameter type 2 (Capability) len 2 23:54:18: BGP: OPEN has CAPABILITY code: 2, length 0 23:54:18: BGP: rcv OPEN w/ option parameter type 2 (Capability) len 8 23:54:18: BGP: OPEN has CAPABILITY code: 129, length 6 23:54:18: BGP: rcv REFRESH_REQ for afi/sfai: 1/1 23:54:18: BGP: start outbound soft reconfig for afi/safi: 1/1 Old style route refresh New style route refresh Initial route refresh Debug output after BGP session reset
© 2001, Cisco Systems, Inc. Multiprotocol BGP-37 Troubleshooting Route Refresh (cont.) Router#debug ip bgp Router#debug ip bgp updates Router#clear ip bgp in 1d00h: BGP: sending REFRESH_REQ(5) for afi/safi: 1/1 1d00h: BGP: rcv UPDATE w/ attr: nexthop , origin i, metric 0, path 2 1d00h: BGP: rcv UPDATE about /8 1d00h: BGP: bumping version for /8 from 0 to 52 1d00h: BGP: nettable_walker /8 calling revise_route 1d00h: BGP: revise route installing /8 -> d00h: BGP: computing updates, neighbor version 51, table version 52, starti ng at d00h: BGP: update run completed, ran for 0ms, neighbor version 51, start ve rsion 52, throttled to 52, check point net d00h: BGP: computing updates, neighbor version 51, table version 52, starti ng at d00h: BGP: send UPDATE /8, next d00h: BGP:, metric 0, path 1 2 1d00h: BGP: updates enqueued (average=45, maximum=45) 1d00h: BGP: update run completed, ran for 0ms, neighbor version 51, start ve rsion 52, throttled to 52, check point net Router#debug ip bgp Router#debug ip bgp updates Router#clear ip bgp in 1d00h: BGP: sending REFRESH_REQ(5) for afi/safi: 1/1 1d00h: BGP: rcv UPDATE w/ attr: nexthop , origin i, metric 0, path 2 1d00h: BGP: rcv UPDATE about /8 1d00h: BGP: bumping version for /8 from 0 to 52 1d00h: BGP: nettable_walker /8 calling revise_route 1d00h: BGP: revise route installing /8 -> d00h: BGP: computing updates, neighbor version 51, table version 52, starti ng at d00h: BGP: update run completed, ran for 0ms, neighbor version 51, start ve rsion 52, throttled to 52, check point net d00h: BGP: computing updates, neighbor version 51, table version 52, starti ng at d00h: BGP: send UPDATE /8, next d00h: BGP:, metric 0, path 1 2 1d00h: BGP: updates enqueued (average=45, maximum=45) 1d00h: BGP: update run completed, ran for 0ms, neighbor version 51, start ve rsion 52, throttled to 52, check point net Debug output after route refresh
© 2001, Cisco Systems, Inc. Multiprotocol BGP-38 Summary After completing this section, you should be able to perform the following tasks: Identify the benefits of BGP route refresh extension Monitor BGP route refresh operation on Cisco IOS Use route refresh capability to force neighbors to resend routing information
© 2001, Cisco Systems, Inc. Multiprotocol BGP-39 Review Questions What are the benefits of Route Refresh? What command is used to trigger route refresh?
Outbound Route Filtering © 2001, Cisco Systems, Inc. Multiprotocol BGP-40
© 2001, Cisco Systems, Inc. Multiprotocol BGP-41 Objectives Upon completion of this section, you will be able to perform the following tasks: Identify the benefits of outbound route filtering Explain the outbound route filtering operation Use outbound route filtering to optimize inbound filtering of routing updates
© 2001, Cisco Systems, Inc. Multiprotocol BGP-42 Outbound Route Filter The purpose of outbound route filtering is to reduce the amount of BGP traffic and CPU use needed to process routing updates Routers exchange inbound filter configurations, which are used as outbound filters on neighboring routers Filters are described in ORF entries ORF entries are part of the Route-Refresh message
© 2001, Cisco Systems, Inc. Multiprotocol BGP-43 Inbound vs. Outbound Filtering AS 1AS 2 Standard input filter routes Filter F_IN 100 routes Standard inbound filtering: AS 1AS 2 Use filter F_IN (route refresh with ORF message) Outbound route filtering: routes Filter F_IN 100 routes Output filter received from AS 2
© 2001, Cisco Systems, Inc. Multiprotocol BGP-44 ORF Message ORF message consists of the following fields: AFI/SAFI ORF type When to refresh List of ORF entries ORF entries depend on the ORF type ORF capability needs to be negotiated for every supported ORF type
© 2001, Cisco Systems, Inc. Multiprotocol BGP-45 ORF Types ORF types NLRI (ORF type=1) - filters based on the prefix Communities (ORF type=2) – filters based on standard BGP community attribute Extended Communities (ORF type=3) – filters based on the extended BGP community attribute Prefix list (ORF type=129) – filters based on Cisco implementation of prefix filtering
© 2001, Cisco Systems, Inc. Multiprotocol BGP-46 ORF Example AFI/SAFI is IPv4 Unicast ORF type is NLRI Action: ADD, DELETE or DELETE ALL Match: PERMIT or DENY Scope: EXACT or REFINE NLRI: prefix When: IMMEDIATE or DEFER
© 2001, Cisco Systems, Inc. Multiprotocol BGP-47 ORF Example (cont.) Anti-spoofing filter (does not accept routes for RFC1918 networks): AFI/SAFI = 1/1 (IPv4 unicast) ORF type = 1 (NLRI) When to refresh – IMMEDIATE ORF entries: –ADD DENY REFINE /8 –ADD DENY REFINE /12 –ADD DENY REFINE /16 –ADD PERMIT REFINE /0
© 2001, Cisco Systems, Inc. Multiprotocol BGP-48 ORF Capability Negotiation neighbor neighbor capability prefix-filter router(config-router)# Enables negotiation of prefix-list ORF capability during session set-up ORF-capable BGP speaker will install ORFs per neighbor Allows a neighbor to send a prefix list in route refresh messages neighbor neighbor send prefix-filter router(config-router)# Activates prefix-list ORF for the specified neighbor Neighbor needs to send prefix-list ORF capability in OPEN message for this command to take effect
© 2001, Cisco Systems, Inc. Multiprotocol BGP-49 Using Outbound Route Filtering clear ip bgp neighbor in [prefix-filter] router# Triggers a route-refresh message Includes a prefix-list in the route-refresh message if configured and supported on both ends Prefix list is sent at session set-up Use the “prefix-filter” option to refresh the remote filter
© 2001, Cisco Systems, Inc. Multiprotocol BGP-50 Prefix-list ORF Example Command “send prefix-filter” on one router requires “capability prefixfilter” on neighboring router AS 1AS 2 router bgp 2 neighbor remote-as 1 neighbor capability prefix-filter neighbor send prefix-filter neighbor prefix-list P in ! ip prefix-list P seq 5 deny /8 le 32 ip prefix-list P seq 10 deny /12 le 32 ip prefix-list P seq 15 deny /16 le 32 ip prefix-list P seq 20 permit /0 le 32 router bgp 1 neighbor remote-as 2 neighbor capability prefix-filter
© 2001, Cisco Systems, Inc. Multiprotocol BGP-51 Monitoring Outbound Route Filtering show ip bgp neighbor neighbor router# Verifies the supported capabilities Router#show ip bgp neighbor BGP neighbor is , remote AS 1, external link Index 1, Offset 0, Mask 0x2 BGP version 4, remote router ID BGP state = Established, table version = 42, up for 00:00:12 Last read 00:00:00, last send 00:00:00 Hold time 3, keepalive interval 1 seconds Neighbor NLRI negotiation: Configured for unicast routes only Peer negotiated unicast routes only Exchanging unicast routes only Received route refresh capability(new) from peer Prefixlist ORF: Capability: advertised; received Filter: sent; Minimum time between advertisement runs is 30 seconds... Router#show ip bgp neighbor BGP neighbor is , remote AS 1, external link Index 1, Offset 0, Mask 0x2 BGP version 4, remote router ID BGP state = Established, table version = 42, up for 00:00:12 Last read 00:00:00, last send 00:00:00 Hold time 3, keepalive interval 1 seconds Neighbor NLRI negotiation: Configured for unicast routes only Peer negotiated unicast routes only Exchanging unicast routes only Received route refresh capability(new) from peer Prefixlist ORF: Capability: advertised; received Filter: sent; Minimum time between advertisement runs is 30 seconds...
© 2001, Cisco Systems, Inc. Multiprotocol BGP-52 Summary After completing this section, you should be able to perform the following tasks: Identify the benefits of outbound route filtering Explain the outbound route filtering operation Use outbound route filtering to optimize inbound filtering of routing updates
© 2001, Cisco Systems, Inc. Multiprotocol BGP-53 Review Questions What are the benefits of using the outbound route filtering feature? How does ORF work? List some ORF types How is capability negotiation for prefix-list ORFs enabled? Which command do you use to filter updates on the remote end of the BGP session?
© 2001, Cisco Systems, Inc. Multiprotocol BGP-54 Summary After completing this chapter, you should be able to perform the following tasks: Explain the difference between BGP for unicast IP and MP-BGP for other protocols Describe how routing information for other protocols is carried in MP-BGP updates Describe the detailed operation of the route refresh mechanism Describe outbound route filters
© 2001, Cisco Systems, Inc. Multiprotocol BGP-55
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