BGP-functie voor voorwaardelijke advertenties

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Bijgewerkt:15 juni 2020

Document-id:215634

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Over deze vertaling

Cisco heeft dit document vertaald via een combinatie van machine- en menselijke technologie om onze gebruikers wereldwijd ondersteuningscontent te bieden in hun eigen taal. Houd er rekening mee dat zelfs de beste machinevertaling niet net zo nauwkeurig is als die van een professionele vertaler. Cisco Systems, Inc. is niet aansprakelijk voor de nauwkeurigheid van deze vertalingen en raadt aan altijd het oorspronkelijke Engelstalige document (link) te raadplegen.

Inhoud

Inleiding

Voorwaarden

Vereisten

Gebruikte componenten

Configureren

Netwerkdiagram

Configuraties

Verifiëren

Problemen oplossen

Inleiding

In dit document wordt de BGP-advertenties (Border Gateway Protocol) beschreven die voorzien in extra controle op routeadvertenties, hetgeen afhangt van het bestaan van andere prefixes in de BGP-tabel.

Voorwaarden

Vereisten

Cisco raadt aan dat u kennis hebt van dit onderwerp:

Platform Independent

Gebruikte componenten

De informatie in dit document is gebaseerd op de volgende software- en hardware-versies:

IOS
IOS-XE
ASR 1000 router

De informatie in dit document is gebaseerd op de apparaten in een specifieke laboratoriumomgeving. Alle apparaten die in dit document worden beschreven, hadden een opgeschoonde (standaard)configuratie. Als uw netwerk levend is, zorg er dan voor dat u de mogelijke impact van om het even welke opdracht begrijpt.

Configureren

Configureer R1, R2 en R3. De configuratie wordt hier gegeven.

Netwerkdiagram

Configuraties

Configuratie R1:

!
hostname R1
!
ip cef
!
interface Loopback0
ip address 1.1.1.1 255.255.255.255
! 
interface Loopback1
ip address 1.1.1.2 255.255.255.255
!
interface Loopback2
ip address 1.1.1.3 255.255.255.255
!
interface Loopback3
ip address 1.1.1.4 255.255.255.255
!
interface Loopback4
ip address 1.1.1.5 255.255.255.255
!
interface Loopback100
ip address 10.139.224.1 255.255.240.0
!
interface Ethernet0/0
ip address 10.10.12.1 255.255.255.0
!
router bgp 1
bgp log-neighbor-changes
neighbor 10.10.12.2 remote-as 2
!
address-family ipv4
network 0.0.0.0 route-map DEF
network 1.1.1.1 mask 255.255.255.255 route-map RM1
network 1.1.1.5 mask 255.255.255.255
redistribute connected route-map CUST
neighbor 10.10.12.2 activate
neighbor 10.10.12.2 send-community
neighbor 10.10.12.2 soft-reconfiguration inbound
exit-address-family
!
ip forward-protocol nd
! 
ip bgp-community new-format
ip route 0.0.0.0 0.0.0.0 Null0
!
ip prefix-list CUST seq 5 permit 10.139.224.0/20
!
ip prefix-list DEFAULT seq 5 permit 0.0.0.0/0
!
ip prefix-list PL1 seq 5 permit 1.1.1.1/32
!
route-map CUST permit 10
match ip address prefix-list CUST
set community 64671:501
!
route-map RM1 permit 10
match ip address prefix-list PL1
set community 64952:3008
!
route-map DEF permit 10
match ip address prefix-list DEFAULT
set community 64848:3011 65011:200 65013:200
!
end

R2-configuratie:

!
hostname R2
!
ip cef
!
interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!         
interface Ethernet0/0
 ip address 10.10.12.2 255.255.255.0
!
interface Ethernet0/1
 ip address 10.10.23.2 255.255.255.0
!
router bgp 2
 bgp log-neighbor-changes
 neighbor 10.10.12.1 remote-as 1
 neighbor 10.10.23.3 remote-as 3
 !
 address-family ipv4
  neighbor 10.10.12.1 activate
  neighbor 10.10.12.1 soft-reconfiguration inbound
  neighbor 10.10.23.3 activate
  neighbor 10.10.23.3 send-community
  neighbor 10.10.23.3 advertise-map ADV-MAP exist-map EXIST-MAP <<< This statement changes in non-exist-map
  neighbor 10.10.23.3 soft-reconfiguration inbound
 exit-address-family
!
ip forward-protocol nd
!
ip bgp-community new-format
ip community-list standard DEFAULT-ROUTE permit 65013:200
ip community-list standard DC1-ROUTES permit 64952:3008
ip community-list standard DC2-ROUTES permit 64671:501
ip community-list standard DC3-ROUTES permit 64950:3009
ip community-list standard DEFAULT-ROUTE-DENY deny 65013:200
!
!
ip prefix-list DEFAULT seq 5 permit 1.1.1.5/32
ip prefix-list DEFAULT seq 10 permit 1.1.1.1/32
!
ip prefix-list EXIST seq 5 permit 10.10.10.10/32
!
ip prefix-list DEFAULT-ROUTE seq 5 permit 0.0.0.0/0
!
ip prefix-list DEFAULT-ROUTE-DENY seq 5 deny 0.0.0.0/0
!
ip prefix-list IP1 seq 5 permit 10.139.224.0/20
!
ip prefix-list T2 seq 5 permit 1.1.1.5/32
!
route-map ADV-MAP permit 10
 match ip address prefix-list IP1
!
route-map ADV-MAP permit 20
 match community DC1-ROUTES DC2-ROUTES DC3-ROUTES
!
route-map EXIST-MAP permit 10
 description Verify Default Route from MDC-SWG
 match ip address prefix-list DEFAULT-ROUTE IP1
 match community DEFAULT-ROUTE
!
!
end

R3-configuratie:

!
hostname R3
!
ip cef
!
interface Loopback0
 ip address 3.3.3.3 255.255.255.255
!
interface Ethernet0/1
 ip address 10.10.23.3 255.255.255.0
 shutdown
!
router bgp 3
 bgp log-neighbor-changes
 neighbor 10.10.23.2 remote-as 2
 !
 address-family ipv4
  neighbor 10.10.23.2 activate
  neighbor 10.10.23.2 send-community
  neighbor 10.10.23.2 soft-reconfiguration inbound
 exit-address-family
!         
ip forward-protocol nd
!
ip bgp-community new-format
!
!
end

Verifiëren

Voorwaarde 1:

Indien de standaardroute niet aanwezig is in BGP RIB, mag R2 bepaalde routes niet bekendmaken.
Indien de standaardroute aanwezig is in BGP RIB, moet R2 alle routes adverteren.

Bestaande-map gebruiken

Voorwaarde 2:

Indien de standaardroute niet aanwezig is in BGP RIB, moet R2 alle routes bekendmaken.
Indien de standaardroute aanwezig is in BGP RIB, mag R2 bepaalde routes niet bekendmaken.

Gebruik niet-existentiële kaart

R1#show ip bgp 
BGP table version is 7, local router ID is 10.139.224.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          0.0.0.0                  0         32768 i
 *>  1.1.1.1/32       0.0.0.0                  0         32768 i
 *>  1.1.1.5/32       0.0.0.0                  0         32768 i
 *>  10.139.224.0/20  0.0.0.0                  0         32768 ?

R2#show ip bgp 
BGP table version is 11, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          10.10.12.1               0             0 1 i
 *>  1.1.1.1/32       10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i
 *>  10.139.224.0/20  10.10.12.1               0             0 1 ?
R2#show ip bgp 0.0.0.0
BGP routing table entry for 0.0.0.0/0, version 9
Paths: (1 available, best #1, table default)
  Advertised to update-groups:
     1         
  Refresh Epoch 1
  1, (received & used)
    10.10.12.1 from 10.10.12.1 (10.139.224.1)
      Origin IGP, metric 0, localpref 100, valid, external, best
      Community: 64848:3011 65011:200 65013:200
      rx pathid: 0, tx pathid: 0x0

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 11, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          10.10.12.1               0             0 1 i
 *>  1.1.1.1/32       10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i
 *>  10.139.224.0/20  10.10.12.1               0             0 1 ?

Total number of prefixes 4

Condition1 Verification:
========================
If default route is not present in BGP RIB, R2 should not advertise certain routes.
If default route is present in BGP RIB, R2 should advertise all the routes.
Use exist-map

R2's BGP Configuration:
=======================
R2#show running-config | sec bgp
router bgp 2
bgp log-neighbor-changes
neighbor 10.10.12.1 remote-as 1
neighbor 10.10.23.3 remote-as 3
!
address-family ipv4
neighbor 10.10.12.1 activate
neighbor 10.10.12.1 soft-reconfiguration inbound
neighbor 10.10.23.3 activate
neighbor 10.10.23.3 send-community
neighbor 10.10.23.3 advertise-map ADV-MAP exist-map EXIST-MAP
neighbor 10.10.23.3 soft-reconfiguration inbound
exit-address-family
ip bgp-community new-format


When Default route is removed from R2's BGP RIB:
================================================
*Mar 6 09:07:08.833: BGP(0): 10.10.12.1 rcv UPDATE about 0.0.0.0/0 -- withdrawn
*Mar 6 09:07:08.833: BGP(0): no valid path for 0.0.0.0/0
*Mar 6 09:07:08.833: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 0.0.0.0/0
*Mar 6 09:07:08.833: BGP(0): (base) 10.10.23.3 send unreachable (format) 0.0.0.0/0
*Mar 6 09:07:21.280: BPG(0): Condition EXIST-MAP changes to Withdraw
*Mar 6 09:07:21.353: BGP(0): net 1.1.1.1/32 matches ADV MAP ADV-MAP: bump version to 13
*Mar 6 09:07:21.353: BGP(0): net 10.139.224.0/20 matches ADV MAP ADV-MAP: bump version to 14
*Mar 6 09:07:21.362: BGP(0): Revise route installing 1 of 1 routes for 1.1.1.1/32 -> 10.10.12.1(global) to main IP table
*Mar 6 09:07:21.362: BGP(0): Revise route installing 1 of 1 routes for 10.139.224.0/20 -> 10.10.12.1(global) to main IP table
*Mar 6 09:07:38.933: BGP(0): (base) 10.10.23.3 send unreachable (format) 1.1.1.1/32
*Mar 6 09:07:38.933: BGP(0): (base) 10.10.23.3 send unreachable (format) 10.139.224.0/20

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 14, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i

Total number of prefixes 1 


When Default route is added back into R2's BGP RIB: 
===================================================
*Mar  6 09:15:22.883: BGP(0): 10.10.12.1 rcvd UPDATE w/ attr: nexthop 10.10.12.1, origin i, metric 0, merged path 1, AS_PATH , community 64848:3011 65011:200 65013:200
*Mar  6 09:15:22.883: BGP(0): 10.10.12.1 rcvd 0.0.0.0/0
*Mar  6 09:15:22.883: BGP(0): Revise route installing 1 of 1 routes for 0.0.0.0/0 -> 10.10.12.1(global) to main IP table
*Mar  6 09:15:22.883: BGP(0): (base) 10.10.23.3 send UPDATE (format) 0.0.0.0/0, next 10.10.23.2, metric 0, path 1
*Mar  6 09:16:21.759: BPG(0): Condition EXIST-MAP changes to Advertise
*Mar  6 09:16:21.759: BGP(0): net 1.1.1.1/32 matches ADV MAP ADV-MAP: bump version to 16
*Mar  6 09:16:21.759: BGP(0): net 10.139.224.0/20 matches ADV MAP ADV-MAP: bump version to 17
*Mar  6 09:16:21.768: BGP(0): Revise route installing 1 of 1 routes for 1.1.1.1/32 -> 10.10.12.1(global) to main IP table
*Mar  6 09:16:21.769: BGP(0): Revise route installing 1 of 1 routes for 10.139.224.0/20 -> 10.10.12.1(global) to main IP table
*Mar  6 09:16:21.769: BGP(0): (base) 10.10.23.3 send UPDATE (format) 1.1.1.1/32, next 10.10.23.2, metric 0, path 1
*Mar  6 09:16:21.769: BGP(0): (base) 10.10.23.3 send UPDATE (format) 10.139.224.0/20, next 10.10.23.2, metric 0, path 1

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 17, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          10.10.12.1               0             0 1 i
 *>  1.1.1.1/32       10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i
 *>  10.139.224.0/20  10.10.12.1               0             0 1 ?

Total number of prefixes 4

Condition2 Verification:
=========================
If default route is not present in BGP RIB, R2 should advertise all the routes.
If default route is present in BGP RIB, R2 should not advertise certain routes.
Use non-exist-map

R2's BGP Configuration:
=======================
R2#show running-config | sec bgp
router bgp 2
bgp log-neighbor-changes
neighbor 10.10.12.1 remote-as 1
neighbor 10.10.23.3 remote-as 3
!
address-family ipv4
neighbor 10.10.12.1 activate
neighbor 10.10.12.1 soft-reconfiguration inbound
neighbor 10.10.23.3 activate
neighbor 10.10.23.3 send-community
neighbor 10.10.23.3 advertise-map ADV-MAP non-exist-map EXIST-MAP
neighbor 10.10.23.3 soft-reconfiguration inbound
exit-address-family
ip bgp-community new-format


When Default route is removed from R2's BGP RIB:
================================================
*Mar  6 09:21:24.445: BGP(0): 10.10.12.1 rcv UPDATE about 0.0.0.0/0 -- withdrawn
*Mar  6 09:21:24.445: BGP(0): no valid path for 0.0.0.0/0
*Mar  6 09:21:24.445: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 0.0.0.0/0
*Mar  6 09:21:24.445: BGP(0): (base) 10.10.23.3 send unreachable (format) 0.0.0.0/0
*Mar  6 09:22:22.050: BPG(0): Condition EXIST-MAP changes to Advertise
*Mar  6 09:22:22.050: BGP(0): net 1.1.1.1/32 matches ADV MAP ADV-MAP: bump version to 21
*Mar  6 09:22:22.050: BGP(0): net 10.139.224.0/20 matches ADV MAP ADV-MAP: bump version to 22
*Mar  6 09:22:22.060: BGP(0): Revise route installing 1 of 1 routes for 1.1.1.1/32 -> 10.10.12.1(global) to main IP table
*Mar  6 09:22:22.060: BGP(0): Revise route installing 1 of 1 routes for 10.139.224.0/20 -> 10.10.12.1(global) to main IP table
*Mar  6 09:22:22.060: BGP(0): (base) 10.10.23.3 send UPDATE (format) 1.1.1.1/32, next 10.10.23.2, metric 0, path 1
*Mar  6 09:22:22.060: BGP(0): (base) 10.10.23.3 send UPDATE (format) 10.139.224.0/20, next 10.10.23.2, metric 0, path 1

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 22, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.1/32       10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i
 *>  10.139.224.0/20  10.10.12.1               0             0 1 ?

Total number of prefixes 3 


When Default route is added back into R2's BGP RIB:
=====================================================
*Mar  6 09:23:04.461: BGP(0): 10.10.12.1 rcvd UPDATE w/ attr: nexthop 10.10.12.1, origin i, metric 0, merged path 1, AS_PATH , community 64848:3011 65011:200 65013:200
*Mar  6 09:23:04.461: BGP(0): 10.10.12.1 rcvd 0.0.0.0/0
*Mar  6 09:23:04.461: BGP(0): Revise route installing 1 of 1 routes for 0.0.0.0/0 -> 10.10.12.1(global) to main IP table
*Mar  6 09:23:04.461: BGP(0): (base) 10.10.23.3 send UPDATE (format) 0.0.0.0/0, next 10.10.23.2, metric 0, path 1
*Mar  6 09:23:22.090: BPG(0): Condition EXIST-MAP changes to Withdraw
*Mar  6 09:23:22.090: BGP(0): net 1.1.1.1/32 matches ADV MAP ADV-MAP: bump version to 24
*Mar  6 09:23:22.090: BGP(0): net 10.139.224.0/20 matches ADV MAP ADV-MAP: bump version to 25
*Mar  6 09:23:22.103: BGP(0): Revise route installing 1 of 1 routes for 1.1.1.1/32 -> 10.10.12.1(global) to main IP table
*Mar  6 09:23:22.103: BGP(0): Revise route installing 1 of 1 routes for 10.139.224.0/20 -> 10.10.12.1(global) to main IP table
*Mar  6 09:23:35.248: BGP(0): (base) 10.10.23.3 send unreachable (format) 1.1.1.1/32
*Mar  6 09:23:35.248: BGP(0): (base) 10.10.23.3 send unreachable (format) 10.139.224.0/20

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 25, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i

Total number of prefixes 2

	Status bestaan-map	Status Adverse-Map
Als de standaardroute aanwezig is.	Gecombineerde conditionering	ADVIEZEN
Als er geen standaardroute is.	Voorwaarde niet afgesloten	ingetrokken

	Status niet bestaand-map	Status Adverse-Map
Als de standaardroute aanwezig is.	Gecombineerde conditionering	intrekken
Als er geen standaardroute is.	Voorwaarde niet afgesloten	ADVIEZEN

Problemen oplossen

De belangrijke opdracht is debug ip bgp updates die u een backend beweging van routekaarten geven verbonden aan de BGP voorwaardelijke kaart. In groot netwerk lopen voorwaardelijke debug met ACL.

Opmerking: Het BGP-scannerproces wordt elke 60 seconden uitgevoerd, dus zodra we de updates voor de existentiekaart/niet-existentiële kaart hebben, duurt de advertentie-map 60 seconden om geactiveerd te worden.

Bijgedragen door Cisco-engineers

Jaivik Shah
Cisco TAC-ingenieur

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