Implementing Internet and MPLS BGP
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For enterprise network engineers, implementing BGP can be an intimidating task. This presentation was given to address common architectures for internet and MPLS BGP usage, along with best practices.
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Implementing Internet and MPLS BGP
- 1. Implementing & Troubleshooting BGP Tanner 5/23/2008 5/30/2008
- 2. Agenda PART 1 BGP Fundamentals BGP and the Internet PART 2 BGP and the WAN Troubleshooting 2
- 3. PART 1 BGP Fundamentals BGP and the Internet 3
- 5. Where is BGP used? Internet Same, Unique, or Mixed ASN MPLS WAN Public or Private ASN 5
- 6. ASAutonomous Systems Textbook answer: An AS is a connected group of one or more IP prefixes run by one or more network operators which has a SINGLE and CLEARLY DEFINED routing policy. 6
- 7. ASN’sAutonomous System Numbers 16-bit ASN’s (RFC1930) Range: 0-65535 Public: 1-64511 Private: 64512-65534 32-bit ASN’s (RFC4893) 4-octets 0.0 to 65535.65535 Only 46 32-bit ASN’s currently allocated 7
- 8. EIGRP and BGP Comparison 8
- 9. Path Selection Attributes Highest Weight Highest Local Preference Internally Originated Shortest AS-Path Manipulating these attributes changes BGP path selection 9
- 10. Terminology attribute [noun] Pronunciation: -trə-byüt 3: a word ascribing a quality; especially attribute [transitive verb] Pronunciation: -tri-byüt, -byət 1: to explain by indicating a cause <attributed his success to his coach> 10
- 11. BGP AttributesRFC1771 attributes its success to its attributes 11
- 12. BGP AttributesMost Used Influence INBOUNDTraffic The transit path to you is determined by how you announce your routes AS Path Prepend (shorter is more preferred) route-map RM-ISP-OUT set as-path prepend123 123 123 Influence OUTBOUNDtraffic Local Preference (higher is more preferred) route-map RM-ISP-IN set local-preference 50 12
- 13. BGP Process Operations 13
- 14. Section ReviewFundamentals What is an autonomous system? What are BGP attributes that affect inbound traffic? What are BGP attributes that affect outbound traffic? Name 4 common BGP path selection criteria What maintenance task happens every 60 seconds in BGP? 14
- 15. BGP & the Internet 15 23nd Ave / I-40 Junction
- 16. Global IP Assignments IANA Regional Registrars ISP’s End Users 16
- 17. Address Space DepletionBGP Movie (6 min) 17
- 18. Global Routing tableHow large is it? .:: Limit Prefixes on Cisco routers router bgp 12345 neighbor 1.1.1.1 maximum-prefix 300000 90 18
- 20. Typical ISP Routing Options Single-homed, Single ISP Private AS or Static (No BGP) Multi-homed, Single ISP Private AS Multi-homed, Dual ISP Public AS 20
- 21. Prefix OriginationInbound Traffic Common Elements ISP’s won’t accept anything longer than /24 Provider Aggregate address block (PA) /24 or shorter from ISP Justification paperwork, but usually easy Announcing another ISP’s prefix Provider Independent address block (PI) Applied for from RIR (e.g., ARIN) More Paperwork (and solid justification)! 21
- 22. What Kind of Routes?Outbound Traffic 1Based on 2 upstream eBGP peers 2 Varies depending on quantity of ISP customers announcing prefixes 3Varies depending on size of upstream carrier 4 Inbound bogon filtering is still possible, however outbound will not function due to default route 22
- 24. BGP Policy Components Prefix-lists to filter prefixes ip prefix-list PL-ANNOUNCE seq 10 permit 1.0.0.0/8 Filter-lists to filter ASNs ip as-path access-list 1 ^1234 Route-maps to apply policy route-map RM-ISP-OUT permit 10 set as-path prepend 1234 Distribute-lists to sit and watch (don’t use) Source: NANOG 23, Phillip Smith 24
- 25. Configuration ExampleISP eBGP Peer with Partial Routes router bgp 1234 no auto-summary no synchronization no bgp fast-external-fallover bgp log-neighbor-changes neighbor 192.0.2.233 remote-as 209 neighbor 192.0.2.233 description eBGP with Qwest AS209. Password: 1234abcd neighbor 192.0.2.233 password 1234abcd neighbor 192.0.2.233 version 4 neighbor 192.0.2.233 soft-reconfiguration inbound neighbor 192.0.2.233 maximum-prefix 300000 90 warning-only neighbor 192.0.2.233 prefix-list PL-BOGONS in neighbor 192.0.2.233 prefix-list PL-ANNOUNCE out neighbor 192.0.2.233 route-map RM-QWEST-OUT out neighbor 192.0.2.233 route-map RM-QWEST-IN in neighbor 192.0.2.233 filter-list 1 out neighbor 192.0.2.233 filter-list 10 in network 205.93.251.0 mask 255.255.254.0 network 205.93.251.0 ip route 205.93.251.0 255.255.254.0 Null0 name BGP-STABILITY ip route 205.93.251.0 255.255.255.0 205.93.251.4 ip route 205.93.251.125 255.255.255.255 205.93.251.121 name IBGP-PEER ip route 205.93.251.125 255.255.255.255 205.93.251.2 250 name IBGP-PEER-BACKUP ip as-path access-list 1 permit ^$ ip as-path access-list 10 permit _(209|7018)$ ip prefix-list PL-ANNOUNCE seq 10 permit 205.93.251.0/23 le 24 ip prefix-list PL-ANNOUNCE seq 99 deny 0.0.0.0/0 le 32 route-map RM-QWEST-OUT permit 10 set as-path prepend 1234 1234 route-map RM-QWEST-IN permit 10 set local-pref 50 25
- 26. Regular ExpressionsBGP AS Filtering Defining our AS ip as-path access-list 1 permit ^$ Originating in AS 3549 ip as-path access-list 1 permit ^3549$ Originating in AS 3549 or Upstream AS ip as-path access-list 1 permit ^3549$ ip as-path access-list 1 permit ^3549 1239$ ip as-path access-list 1 permit ^3549_(1239)?$ Deny all nets originating from AS 1239 and permit all other routes ip as-path access-list 1 deny _1239$ ip as-path access-list 1 permit .* 26
- 27. BGP Routing Table Analysis Daily BGP Stats Available BGP routing table entries examined: 255572 Prefixes after maximum aggregation: 127106 Deaggregation factor: 2.01 Unique aggregates announced to Internet: 123962 Total ASes present in the Internet Routing Table: 28151 Prefixes per ASN: 9.08 Average AS path length visible in the Internet Routing Table: 3.6 Max AS path length visible: 25 Max AS path prepend of ASN (39375) 13 Prefixes from unregistered ASNs in the Routing Table: 25414 Unregistered ASNs in the Routing Table: 1885 Prefixes being announced from unallocated address space: 786 Number of addresses announced to Internet: 1,851,293,088 WojciechMisiaszek TelekomunikacjaPodlasie Sp. ul. Dobra 14A 15-034 Bialystok Poland 27
- 28. Bogon FilteringManual Method 28 Outbound traffic (via inbound route filter) ip prefix-list BOGONS descBogon networks we won't accept ip prefix-list BOGONS seq 2 deny 0.0.0.0/0 ip prefix-list BOGONS seq 5 deny 0.0.0.0/8 le 32 ip prefix-list BOGONS seq 20 deny 5.0.0.0/8 le 32 ip prefix-list BOGONS seq 390 deny 127.0.0.0/8 le 32 ip prefix-list BOGONS seq 400 deny 172.16.0.0/12 le 32 ip prefix-list BOGONS seq 520 deny 224.0.0.0/3 le 32 ip prefix-list BOGONS seq 700 permit 0.0.0.0/0 le 27 Inbound traffic ip access-list extended ACL-OUTSIDE-IN remark --- Basic Spoof Filtering deny ip 0.0.0.0 0.255.255.255 any deny ip 10.0.0.0 0.255.255.255 any deny ippublic-ip-blocksubnet-mask any
- 29. Bogon FilteringAutomatic Method Do not try this at home! Make sure you are aware of potential complications 29 router bgp <your asn> neighbor x.x.x.x remote-as 65333 neighbor x.x.x.xebgp-multihop 255 neighbor x.x.x.x description CymruBogon Route Server Project neighbor x.x.x.x prefix-list PL-CYMRU-OUT out neighbor x.x.x.x route-map RM-CYMRUBOGONS-IN in neighbor x.x.x.x password 31337PW neighbor x.x.x.x maximum-prefix 100 threshold 90 Configure a community list to accept the bogon prefixes into the route-map. ipbgp-community new-format ip community-list 10 permit 65333:888 Configure the route-map. Remember to apply it to the proper peering sessions. route-map RM-CYMRUBOGONS-IN permit 10 description Filter bogons learned from cymru.com bogon route-servers match community 10 set ip next-hop 192.0.2.1 Set a bogon next-hop on all routers that receive the bogons. ip route 192.0.2.1 255.255.255.255 null0 ip prefix-list PL-CYMRU-OUT seq 5 deny 0.0.0.0/0 le 32
- 30. BGP Communities WELL KNOWN TE Custom Communities no-advertise no-export ISP must support it TE via AS path prepends, local prefs, trig. blackhole 30
- 31. BGP CommunitiesConfiguration Example ipbgp-community new-format ipprefix-list PL-ANNOUNCE seq 10 permit 205.93.251.0/24 ipprefix-list PL-ANNOUNCE seq 10 deny 0.0.0.0/0 le 32 route-map RM-ISP-OUT permit 10 match ip address prefix-list PL-ANNOUNCE set community 65011:209 route-map RM-ISP-OUT permit 20 router bgp 64512 neighbor 1.1.1.1 send-community neighbor 1.1.1.1 route-map RM-ISP-OUT out 31
- 32. Section ReviewBGP & the Internet What kind of route options are typically received from an ISP? Who is the global controller of IP space on the internet? Describe bogon filtering What do the ^ and $ symbols mean in regular expressions? 32
- 33. PART 2 BGP and the MPLS WAN Troubleshooting BGP 33
- 34. BGP & MPLS Theory Design Configuration Best Practices 34
- 35. MPLS Basics Topology Full Mesh Single peer to WAN cloud L1 Transport T1 DS3 L2 Transport PPP / MLP ATM / IMA Frame Relay Ethernet Routing Protocols BGP EIGRP RIP Public/Private AS’s 35
- 36. MPLS Terminology CE Router Customer Edge PE Router Provider Edge P/LSR Router Provider Backbone/Label Switching Router VRF Virtual Routing and Forwarding Everything else is standard BGP! 36
- 37. Typical MPLS Topology Options Single-homed, Single ISP Easiest routing policies Multi-homed, Single ISP Most common Multi-homed, Dual Provider Lots of TE 37
- 38. BGP TableHow do you read this thing??? 38 > is the path installed in the routing table rmeans there is already a route with a better AD 32768means prefix originated on this router ? means prefix was originated via redistribution Next Hopis the neighbor IP of eBGP peer(s) WAN-Router# shipbgp BGP table version is 7345, local router ID is 172.16.254.3 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path * i12.86.42.44/30 172.16.254.4 0 100 0 7018 ? *> 12.122.14.185 0 7018 ? r>i172.16.254.4/32 172.16.254.4 0 100 0 ? *> 172.16.254.16/29 0.0.0.0 0 32768 ? *> 172.16.254.24/29 0.0.0.0 0 32768 ? * i172.30.32.0/20 172.16.254.4 0 100 0 7018 7018 i *> 12.122.14.185 0 7018 7018 i *> 172.30.64.0/20 12.122.14.185 0 7018 7018 ? imeans prefix was originated via network statement AS set is the list of AS’s prefix has passed through CIDR Mask try to summarize where possible * means route is OK to inject in routing table imeans prefix learned from iBGP peer
- 39. Default Route Origination 39 *Policies include: Conditional advertisement, AS prepending, and communities
- 40. Best Path Selection Review BGP Table (BRIB) Routing Table (RIB) BGP Multipath Multi-VRF w/Sub-interfaces 40 Weight Local Pref Local Originate AS Path Origin Type Lowest MED eBGP over iBGP IGP Metric to NH Received First Lowest RID Originator ID Neighbor IP WAN-router# shipbgpnei 172.16.16.249 advertised-routes Originating default network 0.0.0.0 Network Next Hop Metric LocPrf Weight Path *> 10.0.0.0/24 10.20.40.5 0 32768 ? *> 10.20.20.0/24 0.0.0.0 0 32768 ? ... Only send the very best! WAN-router> shipbgp Network Next Hop Metric LocPrf Weight Path *> 0.0.0.0 172.14.16.250 0 65000 i * 0.0.0.0 10.217.13.102 0 65001 i WAN-router> shipbgp Network Next Hop Metric LocPrf Weight Path *> 0.0.0.0 172.11.132.193 0 1803 65000 i
- 41. Route Redistribution “Seek first to summarize…” Do you need to redistribute? Yes = Redistribution No = Summarization Maybe = Both? BGP to EIGRP router eigrp 111 redistribute bgp 222 metric 1500 1000 255 1 1500 EIGRP to BGP router bgp 222 redistribute eigrp 111 41
- 42. Miscellaneous Features Peer Groups Object-groups for BGP! (Kind of…) router bgp 64512 ! Setup peer-group policies neighbor PARTIAL-ROUTES peer-group neighbor PARTIAL-ROUTES version 4 neighbor PARTIAL-ROUTES filter-list 5 out neighbor FULL-ROUTES peer-group neighbor FULL-ROUTES version 4 ! Apply it to a neighbor neighbor 192.0.2.228 peer-group FULL-ROUTES ip as-path access-list 5 permit ^(209|36270|6298_)[0-9]*_[0-9]*$ Route Reflectors 42
- 43. Best Practices Avoid redistributing everything under the sun connected, static, every routing protocol, etc. Look for ways to reduce routing tables Summarize Advertise only what is necessary Use a network statement for default origination network 0.0.0.0 mask 0.0.0.0 43
- 44. Case StudyRequirements WAN to Internet Use DC as primary Use Campus as secondary Use Internet VPN as tertiary WAN to Hubs Use each hub MPLS DS3 Use other hub DS3 as secondary Use Internet VPN as tertiary Hub to Hub Use LAN link as primary Don’t use MPLS DS3’s as secondary 44 Smokey the Router says… “Routing works both ways!”
- 46. Use DC as primary
- 47. Use Campus as secondary
- 48. Use Internet VPN as tertiary
- 49. WAN to Hubs
- 50. Use each hub MPLS DS3
- 51. Use other hub DS3 as secondary
- 52. Use Internet VPN as tertiary
- 53. Hub to Hub
- 54. Use LAN link as primary
- 55. Don’t use MPLS DS3’s as secondaryDefault Networks: 1 via eBGP to MPLS 1 via iBGP to VPN Advertised Networks: Shortest AS path (DC) Advertised Networks: network 0.0.0.0 network 10.112.0.0 Received Networks: 0.0.0.0/0 ge 29 le 32 Advertised Networks: network 0.0.0.0 Received Networks: 0.0.0.0/0 ge 29 le 32 Summarized Networks: summary-addr 10.x.0.0/20 summary-addr <WAN nets> Advertised Networks: network 0.0.0.0 Received Networks: 0.0.0.0/0 ge 29 le 32 Summarized Networks: summary-addr 10.112.0.0/16 Default Route Static route redistributed into EIGRP Campus to WAN: EIGRP Metric better via Router 1 WAN DC to Campus: Only 1 route via Interlink
- 56. Configuration Example (Hub)MPLS eBGP Peer with Default Advertisement 46 router bgp 100 network 0.0.0.0 network 10.112.0.0 mask 255.255.0.0 neighbor 192.0.2.105 remote-as 65000 neighbor 192.0.2.105 description eBGP with MPLS SP. Password: 1234abcd neighbor 192.0.2.105 password 1234abcd neighbor 192.0.2.105 version 4 neighbor 192.0.2.105 send-community neighbor 192.0.2.105 soft-reconfiguration inbound neighbor 192.0.2.105 route-map RM-MPLS-IN in neighbor 192.0.2.105 route-map RM-MPLS-OUT out no auto-summary ip prefix-list PL-DEFAULT seq 10 permit 0.0.0.0/0 route-map RM-MPLS-IN deny 10 description Block learning default route from DC Router. Use IGP instead. match ip address prefix-list PL-DEFAULT route-map RM-MPLS-IN permit 20 route-map RM-MPLS-OUT permit 10 description Set BGP policies for outbound route advertisements to MPLS Provider set community 112 route-map RM-MPLS-OUT permit 20 description Prepend Default Route for Backup Link match ip address prefix-list PL-DEFAULT set as-path prepend 100 100 route-map RM-MPLS-OUT permit 30
- 57. Configuration Example (Hub)MPLS EIGRP Redistribution router eigrp 1 redistribute bgp 100 metric 1500 1000 255 1 1500 route-map PL-WAN-SERIALS network 10.112.2.0 0.0.0.255 no auto-summary ip prefix-list PL-WAN-SERIALS seq 10 permit 0.0.0.0/0 ge 29 route-map RM-WAN-SERIALS permit 10 description Only redistribute WAN serials (/29 to /32 prefixes) into EIGRP process match ip address prefix-list PL-WAN-SERIALS Advertise learned BGP networks with prefixes /29 or longer 47
- 58. Section ReviewBGP & MPLS What are the 3 default route origination methods? What does the > symbol mean in the BGP table? What are 3 clues that tell you a route "originated here" in the BGP table? 48
- 59. BGP Troubleshooting Interpreting and Troubleshooting BGP Operations 49
- 60. Peer Establishment Peer Reachability MD5 Password Mismatch Wrong neighbor IP Wrong update-source Wrong peer AS TTL / ebgp-multihop Stuck in OpenSent/OpenConfirm Asymmetric routing & TTL problem ACL’s between peers Blocking TCP/179 50
- 61. Flapping Peer *May 20 04:02:39.240 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Down Peer closed the session *May 20 04:02:54.468 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Up *May 20 04:20:44.999 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Down BGP Notification sent *May 20 04:20:44.999 MST: %BGP-3-NOTIFICATION: sent to neighbor 192.0.2.133 4/0 (hold time expired) 0 bytes *May 20 04:21:04.243 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Up *May 20 04:52:18.132 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Down BGP Notification sent *May 20 04:52:18.132 MST: %BGP-3-NOTIFICATION: sent to neighbor 192.0.2.133 4/0 (hold time expired) 0 bytes *May 20 04:55:16.469 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Up *May 20 04:56:17.169 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Down Peer closed the session *May 20 04:56:36.533 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Up *May 20 05:09:28.555 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Down Peer closed the session *May 20 05:09:35.087 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Up *May 20 05:47:57.350 MST: %BGP-5-ADJCHANGE: neighbor 192.0.2.133 Down BGP Notification sent Remote router rebooting (BGP crash?) MTU Incorrect L2 Problem Interface output drops (QoS, CoPP, etc.) 51
- 62. Received RoutesPre/Post Filter Show received routes before policy is applied shipbgpnei 1.1.1.1 received-routes Requires soft-reconfiguration inbound (more mem) Show received routes after policy is applied shipbgpnei 1.1.1.1 routes Show AS Paths to via all neighbors BGP-router> shipbgp paths Address Hash Refcount Metric Path 0xC4125EDC 1 8 0 7018 209 701 23520 3816 ? 0x68397C58 1 18 0 4323 6389 6198 27266 25747 i 0x74151970 1 2 0 4323 1299 13249 44600 i 0x70FF72D4 1 2 0 4323 3257 1241 20506 i 52
- 63. Missing Routes Next hop IP address must be accessible iBGP next-hop-self Route with better AD already exists in RIB Filters Prefix AS-Path Route-maps 53
- 66. Looking GlassPublic BGP Route Servers - CLI Verify how the global internet routing table views your prefix announcement route-views.oregon-ix.net> shipbgp205.93.251.0 | i64512 3333 3356 1239 4323 64512 2905 701 209 7018 64512 4513 13789 22212 4323 64512 7018 4323 64512 ... 56
- 67. Looking GlassPublic BGP Route Servers – Web/CLI 57
- 68. High CPU BGP-Router# sh proc cpu | i CPU|PID|BGP CPU utilization for five seconds: 93%/2%; one minute: 32%; five minutes: 22% PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process 319 2319628 11589466 200 0.15% 0.05% 0.04% 0 BGP Router 320 568684 2305861 246 0.00% 0.01% 0.00% 0 BGP I/O 321 246815548 1497615 164807 76.47% 9.23% 6.50% 0 BGP Scanner 58
- 69. High Memory L3-Switch# sh proc mem | i PID|BGP PID TTY Allocated Freed Holding GetbufsRetbufs Process 319 0 541682808 353471992 177441136 0 0 BGP Router 320 0 1377432 2361312 7048 0 0 BGP I/O 321 0 136 323920 10216 0 0 BGP Scanner L3-Switch# shipbgp sum Neighbor V AS MsgRcvdMsgSentTblVerInQOutQ Up/Down State/PfxRcd 32.124.75.251 4 209 1741759 68344 9564122 0 0 6w5d 251577 52.111.238.129 4 5555 2798645 68231 9564122 0 0 1w2d 254104 192.0.1.148 4 22222 68448 2134480 9564122 0 0 3w3d 35 192.0.2.228 4 33333 67386 2381477 9564122 0 0 5d01h 118 192.0.3.254 4 11111 2140027 2272911 9564130 0 0 6w5d 254360 750K routes (if no soft-reconfig) 1.5M routes (if soft-reconfig) 542MB of memory for BGP 59
- 70. LatencyPerception v. Reality What could cause this horrible latency??? Reply from 209.85.171.100: bytes=32 time=5ms TTL=247 Reply from 209.85.171.100: bytes=32 time=5ms TTL=247 Reply from 209.85.171.100: bytes=32 time=6ms TTL=247 Reply from 209.85.171.100: bytes=32 time=99ms TTL=247 Reply from 209.85.171.100: bytes=32 time=225ms TTL=247 Reply from 209.85.171.100: bytes=32 time=248ms TTL=247 Reply from 209.85.171.100: bytes=32 time=66ms TTL=247 Reply from 209.85.171.100: bytes=32 time=8ms TTL=247 Reply from 209.85.171.100: bytes=32 time=5ms TTL=247 Reply from 209.85.171.100: bytes=32 time=5ms TTL=247 60 BGP scanner process takes higher priority than ICMP processing. Move on, nothing to see here.
- 71. Section ReviewTroubleshooting What are 3 reasons that could cause peer establishment problems? What are the advantages and disadvantages of soft reconfiguration? What is required in ordered to announce a prefix? What kind of information can you get from the looking glass route servers? 61
- 72. BGP Resources North American Network Operators Group (NANOG) http://www.nanog.org www.traceroute.org 62
Notes de l'éditeur
- http://tools.ietf.org/html/rfc1930http://www.iana.org/assignments/as-numbers
- http://tools.ietf.org/html/rfc1930http://tools.ietf.org/html/rfc4893http://www.iana.org/assignments/as-numbers
- BGP Scannerhttp://www.cisco.com/warp/public/459/highcpu-bgp.html
- BGP Path Selection BGP could possibly receive multiple advertisements for the same route from multiple sources. BGP selects only one path as the best path. When the path is selected, BGP puts the selected path in the IP routing table and propagates the path to its neighbors. BGP uses the following criteria, in the order presented, to select a path for a destination: •If the path specifies a next hop that is inaccessible, drop the update. •Prefer the path with the largest weight. •If the weights are the same, prefer the path with the largest local preference. •If the local preferences are the same, prefer the path that was originated by BGP running on this router. •If no route was originated, prefer the route that has the shortest AS_path. •If all paths have the same AS_path length, prefer the path with the lowest origin type (where IGP is lower than EGP, and EGP is lower than incomplete). •If the origin codes are the same, prefer the path with the lowest MED attribute. •If the paths have the same MED, prefer the external path over the internal path. •If the paths are still the same, prefer the path through the closest IGP neighbor. •Prefer the path with the lowest IP address, as specified by the BGP router ID.
- http://www.cisco.com/en/US/docs/internetworking/technology/handbook/bgp.html#wp1020565
- http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00801c4f48.shtmlBGP-Router# sh proc cpu | i CPU|PID|BGPCPU utilization for five seconds: 10%/4%; one minute: 6%; five minutes: 5% PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process 215 3212220 28919634 111 0.00% 0.05% 0.07% 0 BGP Router 234 937744 13995769 67 0.00% 0.01% 0.00% 0 BGP I/O 235 38969228 512967 75969 6.14% 0.77% 0.63% 0 BGP Scanner
- http://www.iana.org/assignments/ipv4-address-spacehttp://en.wikipedia.org/wiki/Regional_Internet_RegistryThe Internet Assigned Numbers Authority (IANA) delegates Internet resources to the RIRs, and in turn, the RIRs follow their regional policies for further sub-delegation of resources to their customers, which include Internet service providers and end-user organizations.
- http://www.arin.net/announcements/20070521.htmlhttp://www.networkworld.com/news/2007/060707-arin-registry-backs-ipv6.htmlhttp://en.wikipedia.org/wiki/IPv4_address_exhaustionhttp://www.oecd.org/dataoecd/7/1/40605942.pdf
- Memory Requirementshttp://bgp.potaroo.net/http://bgp.potaroo.net/bgprpts/rva-index.htmlhttp://www.cidr-report.org/as2.0/#General_Statushttp://www.caida.org/research/topology/as_core_network/http://thyme.apnic.net/http://thyme.apnic.net/current/data-summaryneighbor maximum-prefixWhen the number of received prefixes exceeds the maximum number configured, the router terminates the peering (by default). However, if the warning-only keyword is configured, the router instead only sends a log message, but continues peering with the sender. If the peer is terminated, the peer stays down until the clear ipbgpcommand is issued.
- http://www.iana.org/assignments/ipv4-address-spacehttp://www.iana.org/numbershttp://www.afrinic.net/statistics/resource_search.htmhttp://www.arin.net/reference/ip_blocks.html
- http://www.nanog.org/mtg-0710/smith.html
- Full, No DefaultMost organizations don’t need full routesPartial, with DefaultGood balance between load sharing and memory control. ISP or CE controlledDefault OnlyLowest memory requirements, but least amount of available BGP policy options
- http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a92.shtmlhttp://www.911networks.com/index.php/Cisco/BGPRegexOriginated in AS 31915 + allow prependingip as-path access-list 1 permit ^(31915_)+$Use “show ipbgpregex” to test
- http://thyme.apnic.net/current/data-summary
- http://www.team-cymru.org/Services/Bogons/routeserver.htmlhttp://www.team-cymru.org/Services/ip-to-asn.html#whoishttp://www.ietf.org/rfc/rfc2827.txtThe bogon prefixes are announced unaggregated; as of 28 SEP 2005 this includes 71 prefixes. The ASN used by all of the bogon route-servers is 65333. A private ASN is used to ensure that leakage is easily detected and prevented. Each prefix is tagged with a community, 65333:888, to more readily enable filtering. Peering sessions include the use of a password. The bogon route-servers accept no prefixes from their peers.
- BGP community policies can be found in the whois database for the ISP ASNhttp://www.onesc.net/communities/Sprint - https://www.sprint.net/index.php?p=policy_bgp
- http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801475b2.shtml
- http://www.cisco.com/en/US/docs/ios/12_0t/12_0t5/feature/guide/VPN.htmlEach VPN is associated with one or more VPN routing/forwarding instances (VRFs). A VRF defines the VPN membership of a customer site attached to a PE router. A VRF consists of an IP routing table, a derived Cisco Express Forwarding (CEF) table, a set of interfaces that use the forwarding table, and a set of rules and routing protocol parameters that control the information that is included into the routing table.Based on routing information stored in the VRF IP routing table and VRF CEF table, packets are forwarded to their destination using MPLS. A PE router binds a label to each customer prefix learned from a CE router and includes the label in the network reachability information for the prefix that it advertises to other PE routers. When a PE router forwards a packet received from a CE router across the provider network it labels the packet with the label learned from the destination PE router. When the destination PE router receives the labeled packet it pops the label and uses it to direct the packet to the correct CE router. Label forwarding across the provider backbone, is based on either dynamic label switching or traffic engineered paths. A customer data packet carries two levels of labels when traversing the backbone: 1 Top label directs the packet to the correct PE router 2 Second label indicates how that PE router should forward the packet to the CE router
- Verizon AT&T AS7018Sprint AS1803
- neighbor 1.1.1.1 default-originate This command does not require the presence of 0.0.0.0 in the local router. When used with a route map, the default route 0.0.0.0 is injected if the route map contains a match ip address clause and there is a route that matches the IP access list exactly. The route map can contain other match clauses also. You can use standard or extended access lists with the neighbor default-originate command.
- http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtmlBGP Multipath BGP Multipath allows installation into the IP routing table of multiple BGP paths to the same destination. These paths are installed in the table together with the best path for load sharing. BGP Multipath does not affect bestpath selection. For example, a router still designates one of the paths as the best path, according to the algorithm, and advertises this best path to its neighbors.
- bgp fast-external-falloverTo immediately reset the BGP sessions of any directly adjacent external peers if the link used to reach them goes down, use thebgp fast-external-fallover command. The behavior of this command is enabled by default.
- http://www.cisco.com/en/US/tech/tk365/tk80/tsd_technology_support_sub-protocol_home.htmlhttp://www.nanog.org/mtg-0802/smith1.htmlhttp://www.nanog.org/mtg-0802/presentations/PSmith_BGP.pdf
- http://www.cisconet.com/route-server/world_map.htmlTelnet to route-views.oregon-ix.net
- http://www.cisconet.com/route-server/world_map.htmlhttp://stat.qwest.net/looking_glass.htmlTelnet to route-views.oregon-ix.net
- http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00801c4f48.shtmlReduce amount of receivedBGP prefixes
- http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00801c4f48.shtmlWhile BGP scanner runs, low priority processes need to wait a longer time to access the CPU. One low priority process controls Internet Control Message Protocol (ICMP) packets such as pings. Packets destined to or originated from the router may experience higher than expected latency since the ICMP process must wait behind BGP scanner. The cycle is that BGP scanner runs for some time and suspends itself, and then ICMP runs. In contrast, pings sent through a router should be switched via Cisco Express Forwarding (CEF) and should not experience any additional latency. When troubleshooting periodic spikes in latency, compare forwarding times for packets forwarded through a router against packets processed directly by the CPU on the router.