Laboratorio sobre routers reflectores de rutas
BGP
Fecha: 12 y 18 de mayo
del 2023
Escenario
Este es un laboratorio que siempre quise hacer
desde que era chico pero nunca me dió
la cabeza la oportunidad, hasta hoy.
Un route
reflector es un router configurado para enviar
actualizaciones a sus vecinos o peers a través del
mismo AS, o sea que
estamos hablando de iBGP
(BGP interior). Básicamente y salvando las distancias, de un modo grosero
podemos decir que se
comporta como un DR en OSPF, haciéndose cargo de
los cálculos y actualizaciones de ruta, y enviándolas a los vecinos (peers).
Este escenario lo vi por primera vez en Arquitecturas
de enrutamiento de internet de Cisco Press
(2004), un libro …algo áspero.
Cuando se habla de topología iBGP
necesitamos armar una malla (mesh) o una conexión
“todos contra todos” y que inicialmente
la hicimos con tres routers,
pero que podrían ser N routers con (N-1)/2 conexiones entre si, lo cual
no es escalable si hablamos
de tantos participantes.
La complejidad de estos
temas pueden aumentar bastante, pero en este lab sólo se
analizarán las actualizaciones entre peers.
1.- Escenario inicial:
Este es el escenario de una malla (mesh) en donde los tres routers
tienen configurados a sus vecinos como peers, o sea
que el
Router BGP-1 tiene a
BGP-3 y BGP-4 como vecinos, el router BGP-3 tiene a
BGP-1 y BGP-4 como vecinos, y el router BGP-4
tiene a BGP-1 y BGP-3. Siempre hablando del AS
65531. Como dijimos, esta topología es válida pero no es escalable.
El backbone del AS
65531 es, si bien vemos un triángulo de tres P2P, una LAN switcheada
en el segmento 181.0.0.0/24, por este motivo
debemos bajar los peers
a nivel BGP y no con shut en alguna interface como en
otros escenarios.
1.1.- Verificación inicial:
Nos aseguramos que todos vean las rutas de todos.
BGP-1#sh ip bgp
BGP table version is 1, local router ID is 181.0.0.1
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
* 181.0.1.0/24 0.0.0.0 0 32768 I (router BGP-1)
* 181.0.2.0/24 0.0.0.0 0 32768 i
* 181.0.3.0/24 0.0.0.0 0 32768 i
* i181.0.4.0/24 181.0.0.2 0 100 0 i (router BGP-3)
* i181.0.5.0/24 181.0.0.2 0 100 0 i
* i181.0.6.0/24 181.0.0.2 0 100 0 i
* i181.0.7.0/24 181.0.0.3 0 100 0 i (router BGP-4)
* i181.0.8.0/24 181.0.0.3 0 100 0 i
* i181.0.9.0/24 181.0.0.3 0
100 0 i
* 200.0.1.0 190.0.0.2 0
65530 i (router BGP-2 en
AS 65530)
* 200.0.2.0 190.0.0.2 0
65530 i
* 200.0.3.0 190.0.0.2 0
65530 i
BGP-1#
BGP-1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP
external, 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
i
- IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 -
IS-IS level-2
ia
- IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic
downloaded static route
Gateway of last resort is not set
190.0.0.0/24 is subnetted, 1 subnets
C 190.0.0.0 is directly
connected, FastEthernet0/0
B
200.0.1.0/24 [20/0] via 190.0.0.2, 00:00:14 (router
BGP-2)
B
200.0.2.0/24 [20/0] via 190.0.0.2, 00:00:14
B
200.0.3.0/24 [20/0] via 190.0.0.2, 00:00:14
181.0.0.0/24 is subnetted,
10 subnets
C 181.0.0.0 is directly
connected, FastEthernet0/1.1810 (backbone
BGP)
C 181.0.1.0 is directly
connected, FastEthernet0/1.1811 (redes
locales)
C 181.0.2.0 is directly
connected, FastEthernet0/1.1812
C 181.0.3.0 is directly
connected, FastEthernet0/1.1813
B
181.0.4.0 [200/0] via 181.0.0.2, 00:00:14 (router
BGP-3)
B 181.0.5.0
[200/0] via 181.0.0.2, 00:00:14
B
181.0.6.0 [200/0] via 181.0.0.2, 00:00:14
B
181.0.7.0 [200/0] via 181.0.0.3, 00:00:14 (router
BGP-3)
B
181.0.9.0 [200/0] via 181.0.0.3, 00:00:16
B
181.0.8.0 [200/0] via 181.0.0.3, 00:00:16
BGP-1#
[admin@BGP-2] > ip route print
Flags: X - disabled, A - active, D - dynamic,
C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme,
B - blackhole, U - unreachable, P - prohibit
# DST-ADDRESS PREF-SRC GATEWAY DISTANCE
0 ADb
181.0.1.0/24 190.0.0.1 20 (redes de BGP-1 vía BGP-1)
1 ADb 181.0.2.0/24 190.0.0.1 20
2 ADb 181.0.3.0/24 190.0.0.1 20
3 ADb 181.0.4.0/24 190.0.0.1 20 (redes de BGP-3 vía BGP-1)
4 ADb 181.0.5.0/24 190.0.0.1 20
5 ADb 181.0.6.0/24 190.0.0.1 20
6 ADb 181.0.7.0/24 190.0.0.1 20 (redes de BGP-4 vía BGP-1)
7 ADb 181.0.8.0/24 190.0.0.1 20
8 ADb
181.0.9.0/24 190.0.0.1 20
9 ADC 190.0.0.0/24 190.0.0.2 ether1 0 (redes locales)
10 ADC 200.0.1.0/24 200.0.1.1 vlan201 0
11 ADC 200.0.2.0/24 200.0.2.1 vlan202 0
12 ADC 200.0.3.0/24 200.0.3.1 vlan203 0
[admin@BGP-2] >
BGP-3#sh ip bgp
BGP table version is 25, local router ID is 181.0.0.2
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
*>i
181.0.1.0/24 181.0.0.1 0 100 0 I (router BGP-1)
*>i
181.0.2.0/24 181.0.0.1 0 100 0 i
*>i
181.0.3.0/24 181.0.0.1 0 100 0 i
*> 181.0.4.0/24 0.0.0.0 0 32768 I (redes locales)
*> 181.0.5.0/24 0.0.0.0 0 32768 i
*> 181.0.6.0/24 0.0.0.0 0 32768 i
*>i
181.0.7.0/24 181.0.0.3 0 100 0 I (router BGP-4)
*>i
181.0.8.0/24 181.0.0.3 0 100 0 i
*>i
181.0.9.0/24 181.0.0.3 0 100 0 i
*>i
200.0.1.0 181.0.0.1 0 100 0 65530 i
(router BGP-2 vía BGP-1)
*>i
200.0.2.0 181.0.0.1 0 100 0 65530 i
*>i
200.0.3.0 181.0.0.1 0 100 0 65530 i
BGP-3#
BGP-3#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP
external, 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
i
- IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 -
IS-IS level-2
ia
- IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic
downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % -
next hop override
Gateway of last resort is not set
181.0.0.0/16 is variably subnetted, 14 subnets, 2 masks
C 181.0.0.0/24 is directly
connected, Vlan1810 (backbone
BGP)
L 181.0.0.2/32 is directly
connected, Vlan1810
B 181.0.1.0/24 [200/0] via
181.0.0.1, 00:00:53 (router
BGP-1)
B 181.0.2.0/24 [200/0] via
181.0.0.1, 00:00:53
B 181.0.3.0/24 [200/0] via
181.0.0.1, 00:00:53
C 181.0.4.0/24 is directly
connected, Vlan1814 (redes
locales)
L 181.0.4.1/32 is directly
connected, Vlan1814
C 181.0.5.0/24 is directly
connected, Vlan1815
L 181.0.5.1/32 is directly
connected, Vlan1815
C 181.0.6.0/24 is directly
connected, Vlan1816
L 181.0.6.1/32 is directly
connected, Vlan1816
B 181.0.7.0/24 [200/0] via
181.0.0.3, 00:04:15 (router
BGP-4)
B 181.0.8.0/24 [200/0] via
181.0.0.3, 00:04:15
B
181.0.9.0/24 [200/0] via 181.0.0.3, 00:04:15
B
200.0.1.0/24 [200/0] via 181.0.0.1, 00:00:53 (router BGP-2 vía BGP-1)
B
200.0.2.0/24 [200/0] via 181.0.0.1, 00:00:53
B
200.0.3.0/24 [200/0] via 181.0.0.1, 00:00:53
BGP-3#
BGP-4#sh ip bgp
BGP table version is 25, local router ID is 181.0.0.3
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
*>i181.0.1.0/24
181.0.0.1 0 100
0 i (router BGP-1)
*>i181.0.2.0/24
181.0.0.1 0 100
0 i
*>i181.0.3.0/24
181.0.0.1 0
100 0 i
*>i181.0.4.0/24
181.0.0.2 0 100
0 i (router BGP-3)
*>i181.0.5.0/24
181.0.0.2 0 100
0 i
*>i181.0.6.0/24
181.0.0.2 0 100
0 i
*> 181.0.7.0/24 0.0.0.0 0 32768 i (redes locales)
*> 181.0.8.0/24 0.0.0.0 0 32768 i
*> 181.0.9.0/24 0.0.0.0 0 32768 i
*>i200.0.1.0
181.0.0.1 0 100
0 65530 i (router BGP-2 vía BGP-1)
*>i200.0.2.0
181.0.0.1 0 100
0 65530 i
*>i200.0.3.0
181.0.0.1 0 100
0 65530 i
BGP-4#
BGP-4#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP
external, 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
i
- IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 -
IS-IS level-2
ia
- IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic
downloaded static route, + - replicated route
Gateway of last resort is not set
181.0.0.0/16 is variably subnetted, 14 subnets, 2 masks
C 181.0.0.0/24 is directly
connected, Vlan1810 (backbone
BGP)
L 181.0.0.3/32 is directly
connected, Vlan1810
B 181.0.1.0/24 [200/0] via
181.0.0.1, 00:01:24 (router
BGP-1)
B
181.0.2.0/24 [200/0] via 181.0.0.1, 00:01:24
B
181.0.3.0/24 [200/0] via 181.0.0.1, 00:01:24
B
181.0.4.0/24 [200/0] via 181.0.0.2, 00:04:46 (router
BGP-3)
B 181.0.5.0/24 [200/0] via
181.0.0.2, 00:04:46
B 181.0.6.0/24 [200/0] via
181.0.0.2, 00:04:47
C 181.0.7.0/24 is directly
connected, Vlan1817 (redes
locales)
L 181.0.7.1/32 is directly
connected, Vlan1817
C 181.0.8.0/24 is directly
connected, Vlan1818
L 181.0.8.1/32 is directly connected,
Vlan1818
C 181.0.9.0/24 is directly
connected, Vlan1819
L 181.0.9.1/32 is directly
connected, Vlan1819
B 200.0.1.0/24 [200/0] via
181.0.0.1, 00:01:26 (router BGP-2 vía
BGP-1)
B
200.0.2.0/24 [200/0] via 181.0.0.1, 00:01:26
B
200.0.3.0/24 [200/0] via 181.0.0.1, 00:01:26
BGP-4#
2.- “Rompemos” el full mesh:
Para romper el full-mesh
no bajamos un enlace sino que desactivamos el peer
BGP-4 en BGP-3, ya que todo el backbone del
AS 65531 esta en una
misma red LAN switcheada (181.0.0.0/24) y sería
alcanzable de todas maneras por otro vínculo.
Al apagar el peering
entre BGP-3 y BGP-4 cada uno no verá las rutas del otro.
2.1.- Apagamos el vecino
BGP-4:
BGP-3#conf t
Enter configuration commands, one per line. End with CNTL/Z.
BGP-3(config)#router bgp 65531
BGP-3(config-router)#neighbor 181.0.0.3 shutdown
BGP-3(config-router)#end
BGP-3#
*May 18 17:41:01.981: %BGP-5-NBR_RESET: Neighbor 181.0.0.3 reset (Admin.
shutdown)
*May 18 17:41:01.981: %BGP-5-ADJCHANGE: neighbor 181.0.0.3 Down Admin.
shutdown
*May 18 17:41:01.981: %BGP_SESSION-5-ADJCHANGE: neighbor 181.0.0.3 IPv4
Unicast topology base removed from session Admin. shutdown
*May 18 17:41:03.265: %SYS-5-CONFIG_I: Configured from console by console
BGP-3#
2.2.- Verificamos:
2.2.1.- En router BGP-3:
BGP-3#sh ip bgp
BGP table version is 25, local router ID is 181.0.0.2
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
*>i
181.0.1.0/24 181.0.0.1 0 100 0 I (router BGP-1)
*>i
181.0.2.0/24 181.0.0.1 0 100 0 i
*>i
181.0.3.0/24 181.0.0.1 0 100 0 i
*> 181.0.4.0/24 0.0.0.0 0 32768 I (redes locales)
*> 181.0.5.0/24 0.0.0.0 0 32768 i
*> 181.0.6.0/24 0.0.0.0 0 32768 I (no hay redes de BGP-4)
*>i
200.0.1.0 181.0.0.1 0 100 0 65530 i
(router BGP-2 vía BGP-1)
*>i
200.0.2.0 181.0.0.1 0 100
0 65530 i
*>i
200.0.3.0 181.0.0.1 0 100 0 65530 i
BGP-3#
BGP-3#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external,
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
i
- IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 -
IS-IS level-2
ia
- IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic
downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % -
next hop override
Gateway of last resort is not set
181.0.0.0/16 is variably subnetted, 11 subnets, 2 masks
C 181.0.0.0/24 is directly
connected, Vlan1810 (backbone
BGP)
L 181.0.0.2/32 is directly
connected, Vlan1810
B 181.0.1.0/24 [200/0] via
181.0.0.1, 00:16:02 (router
BGP-1)
B 181.0.2.0/24 [200/0] via
181.0.0.1, 00:16:02
B 181.0.3.0/24 [200/0] via
181.0.0.1, 00:16:02
C 181.0.4.0/24 is directly
connected, Vlan1814 (redes
locales)
L 181.0.4.1/32 is directly
connected, Vlan1814
C 181.0.5.0/24 is directly
connected, Vlan1815
L 181.0.5.1/32 is directly
connected, Vlan1815
C 181.0.6.0/24 is directly
connected, Vlan1816
L
181.0.6.1/32 is directly
connected, Vlan1816 (no hay más redes de BGP-4)
B
200.0.1.0/24 [200/0] via 181.0.0.1, 00:16:02 (router
BGP-2)
B
200.0.2.0/24 [200/0] via 181.0.0.1, 00:16:02
B
200.0.3.0/24 [200/0] via 181.0.0.1, 00:16:02
BGP-3#
2.2.2.- En router BGP-4:
BGP-4#sh ip bgp
BGP table version is 28, local router ID is 181.0.0.3
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
*>i181.0.1.0/24
181.0.0.1 0 100
0 i (router BGP-1)
*>i181.0.2.0/24
181.0.0.1 0 100
0 i
*>i181.0.3.0/24 181.0.0.1 0 100
0 i
*> 181.0.7.0/24 0.0.0.0 0 32768 i (redes locales)(no hay más
redes de BGP-3)
*> 181.0.8.0/24 0.0.0.0 0 32768 i
*> 181.0.9.0/24 0.0.0.0 0 32768 i
*>i200.0.1.0
181.0.0.1 0
100 0 65530 i (router
BGP-2 vía BGP-1)
*>i200.0.2.0
181.0.0.1 0 100
0 65530 i
*>i200.0.3.0
181.0.0.1 0 100
0 65530 i
BGP-4#
BGP-4#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP
external, 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
i
- IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 -
IS-IS level-2
ia
- IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic
downloaded static route, + - replicated route
Gateway of last resort is not set
181.0.0.0/16 is variably subnetted, 11 subnets, 2 masks
C 181.0.0.0/24 is directly
connected, Vlan1810 (backbone
BGP)
L 181.0.0.3/32 is directly
connected, Vlan1810
B 181.0.1.0/24 [200/0] via
181.0.0.1, 00:16:38 (router
BGP-1)
B 181.0.2.0/24 [200/0] via
181.0.0.1, 00:16:38
B
181.0.3.0/24 [200/0] via 181.0.0.1, 00:16:38
C
181.0.7.0/24 is directly
connected, Vlan1817 (redes locales)(no hay más
redes de BGP-3)
L 181.0.7.1/32 is directly
connected, Vlan1817
C 181.0.8.0/24 is directly connected,
Vlan1818
L 181.0.8.1/32 is directly
connected, Vlan1818
C 181.0.9.0/24 is directly
connected, Vlan1819
L 181.0.9.1/32 is directly
connected, Vlan1819
B 200.0.1.0/24 [200/0] via
181.0.0.1, 00:16:39 (router
BGP-2 vía BGP-1)
B
200.0.2.0/24 [200/0] via 181.0.0.1, 00:16:40
B
200.0.3.0/24 [200/0] via 181.0.0.1, 00:16:40
BGP-4#
2.2.3.- En router BGP-1:
BGP-1#sh ip bgp
BGP table version is 13, local router ID is 181.0.0.1
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
*> 181.0.1.0/24 0.0.0.0 0
32768 I (redes
locales)
*> 181.0.2.0/24 0.0.0.0 0 32768 i
*> 181.0.3.0/24 0.0.0.0 0 32768 i
*>i181.0.4.0/24
181.0.0.2 0 100
0 I (router BGP-3)
*>i181.0.5.0/24
181.0.0.2 0 100
0 I
*>i181.0.6.0/24
181.0.0.2 0 100
0 i
*>i181.0.7.0/24
181.0.0.3 0 100
0 I (router BGP-4)
*>i181.0.8.0/24
181.0.0.3 0 100
0 i
*>i181.0.9.0/24
181.0.0.3 0 100
0 i
*> 200.0.1.0
190.0.0.2 0 65530 i (router
BGP-2 vía BGP-1)
*> 200.0.2.0
190.0.0.2 0 65530 i
*> 200.0.3.0
190.0.0.2 0 65530 i
BGP-1#
BGP-1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP
external, 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
i
- IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 -
IS-IS level-2
ia
- IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic
downloaded static route
Gateway of last resort is not set
B 200.0.1.0/24 [20/0] via
190.0.0.2, 00:17:14 (router
BGP-2)
190.0.0.0/24 is subnetted, 1 subnets
C 190.0.0.0 is directly
connected, FastEthernet0/0
B 200.0.2.0/24 [20/0] via 190.0.0.2, 00:17:14
B 200.0.3.0/24 [20/0] via
190.0.0.2, 00:17:14
181.0.0.0/24 is subnetted, 10 subnets
C 181.0.0.0 is directly
connected, FastEthernet0/1.1810 (backbone
BGP)
C 181.0.1.0 is directly
connected, FastEthernet0/1.1811 (redes
locales)
C 181.0.2.0 is directly
connected, FastEthernet0/1.1812
C 181.0.3.0 is directly
connected, FastEthernet0/1.1813
B
181.0.4.0 [200/0] via 181.0.0.2, 00:17:14 (router
BGP-3)
B
181.0.5.0 [200/0] via 181.0.0.2, 00:17:14
B
181.0.6.0 [200/0] via 181.0.0.2, 00:17:14
B
181.0.7.0 [200/0] via 181.0.0.3, 00:17:14 (router
BGP-4)
B
181.0.8.0 [200/0] via 181.0.0.3, 00:17:17
B
181.0.9.0 [200/0] via 181.0.0.3, 00:17:17
BGP-1#
3.- Escenario con route reflector:
Ahora BGP-1 se comprtará
como un DR en OSPF (salvando las diferencias) y todo cambio en BGP-3, BGP-4 lo
verá vía BGP-1
y todo cambios en BGP-4,
también BGP-3 lo verá vía BGP-1. Recordemos que esto sólo aplica al AS 65531 (iBGP).
3.1.- Configuramos el
reflector de rutas en BGP-1:
BGP-1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
BGP-1(config)#router bgp 65531
BGP-1(config-router)#neighbor 181.0.0.2 route-reflector-client
BGP-1(config-router)#neighbor 181.0.0.3 route-reflector-client
BGP-1(config-router)#end
BGP-1#
Dec 31 22:29:40: %BGP-5-ADJCHANGE: neighbor 181.0.0.2 Down RR client
config change
Dec 31 22:29:40: %BGP-5-ADJCHANGE: neighbor 181.0.0.3 Down RR client
config change
Dec 31 22:29:42: %BGP-5-ADJCHANGE: neighbor 181.0.0.2 Up
Dec 31 22:29:42: %BGP-5-ADJCHANGE: neighbor 181.0.0.3 Up
BGP-1#
3.2.- Verificamos rutas
provenientes de BGP-3:
BGP-1#sh ip bgp 181.0.4.0
BGP routing table entry for 181.0.4.0/24, version 20
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
1
Local, (Received from a RR-client)
181.0.0.2 from 181.0.0.2
(181.0.0.2)
Origin IGP, metric 0, localpref
100, valid, internal, best
BGP-1#
3.3.- Verificamos rutas
provenientes de BGP-4:
BGP-1#sh ip bgp 181.0.7.0
BGP routing table entry for 181.0.7.0/24, version 23
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
1 2
Local, (Received from a RR-client)
181.0.0.3 from 181.0.0.3
(181.0.0.3)
Origin IGP, metric 0, localpref 100, valid, internal, best
BGP-1#
3.4.- Verificamos rutas en
BGP-3:
BGP-3#sh ip bgp
BGP table version is 43, local router ID is 181.0.0.2
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
*>i
181.0.1.0/24 181.0.0.1 0 100
0 I (router BGP-1)
*>i
181.0.2.0/24 181.0.0.1 0 100
0 i
*>i
181.0.3.0/24 181.0.0.1 0 100
0 i
*> 181.0.4.0/24 0.0.0.0 0 32768 I (redes locales)
*> 181.0.5.0/24 0.0.0.0 0 32768 i
*> 181.0.6.0/24 0.0.0.0 0 32768 i
*>i
181.0.7.0/24 181.0.0.3 0 100
0 I (router BGP-4)
*>i
181.0.8.0/24 181.0.0.3 0 100
0 i
*>i
181.0.9.0/24 181.0.0.3 0 100
0 i
*>i
200.0.1.0 181.0.0.1 0 100
0 65530 I (router
BGP-2)
*>i
200.0.2.0 181.0.0.1 0 100
0 65530 i
*>i
200.0.3.0 181.0.0.1 0 100
0 65530 i
BGP-3#
BGP-3#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP
external, 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
i
- IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 -
IS-IS level-2
ia
- IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic
downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % -
next hop override
Gateway of last resort is not set
181.0.0.0/16 is variably subnetted, 14 subnets, 2 masks
C 181.0.0.0/24 is directly
connected, Vlan1810 (backbone
BGP)
L 181.0.0.2/32 is directly
connected, Vlan1810
B 181.0.1.0/24 [200/0] via
181.0.0.1, 00:02:59 (router
BGP-1)
B 181.0.2.0/24 [200/0] via
181.0.0.1, 00:02:59
B 181.0.3.0/24 [200/0] via
181.0.0.1, 00:02:59
C 181.0.4.0/24 is directly
connected, Vlan1814 (redes
locales)
L 181.0.4.1/32 is directly
connected, Vlan1814
C 181.0.5.0/24 is directly
connected, Vlan1815
L 181.0.5.1/32 is directly
connected, Vlan1815
C 181.0.6.0/24 is directly
connected, Vlan1816
L 181.0.6.1/32 is directly
connected, Vlan1816
B 181.0.7.0/24 [200/0] via 181.0.0.3, 00:02:59 (router
BGP-4)
B
181.0.8.0/24 [200/0] via 181.0.0.3, 00:02:59
B
181.0.9.0/24 [200/0] via 181.0.0.3, 00:02:59
B
200.0.1.0/24 [200/0] via 181.0.0.1, 00:02:59 (router
BGP-2)
B
200.0.2.0/24 [200/0] via 181.0.0.1, 00:02:59
B
200.0.3.0/24 [200/0] via 181.0.0.1, 00:02:59
BGP-3#
3.5.- Verificamos rutas en
BGP-4:
BGP-4#sh ip bgp
BGP table version is 43, local router ID is 181.0.0.3
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
*>i181.0.1.0/24
181.0.0.1 0 100
0 I (router BGP-1)
*>i181.0.2.0/24
181.0.0.1 0 100
0 i
*>i181.0.3.0/24
181.0.0.1 0 100
0 i
*>i181.0.4.0/24
181.0.0.2 0 100
0 I (router BGP-3)
*>i181.0.5.0/24
181.0.0.2 0 100
0 i
*>i181.0.6.0/24
181.0.0.2 0 100
0 i
*> 181.0.7.0/24 0.0.0.0 0 32768 I (redes
locales)
*> 181.0.8.0/24 0.0.0.0 0 32768 i
*> 181.0.9.0/24 0.0.0.0 0 32768 i
*>i200.0.1.0
181.0.0.1 0
100 0 65530 I (router BGP-2 vía BGP-1)
*>i200.0.2.0
181.0.0.1 0 100
0 65530 i
*>i200.0.3.0
181.0.0.1 0 100
0 65530 i
BGP-4#
BGP-4#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP
external, 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
i
- IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 -
IS-IS level-2
ia
- IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded
static route, + - replicated route
Gateway of last resort is not set
181.0.0.0/16 is variably subnetted, 14 subnets, 2 masks
C 181.0.0.0/24 is directly
connected, Vlan1810 (backbone
BGP)
L 181.0.0.3/32 is directly
connected, Vlan1810
B 181.0.1.0/24 [200/0] via
181.0.0.1, 00:04:03 (router
BGP-1)
B
181.0.2.0/24 [200/0] via 181.0.0.1, 00:04:03
B
181.0.3.0/24 [200/0] via 181.0.0.1, 00:04:03
B
181.0.4.0/24 [200/0] via 181.0.0.2, 00:04:03 (router BGP-3)
B 181.0.5.0/24 [200/0] via 181.0.0.2, 00:04:03
B 181.0.6.0/24 [200/0] via 181.0.0.2, 00:04:04
C 181.0.7.0/24 is directly
connected, Vlan1817 (redes
locales)
L 181.0.7.1/32 is directly
connected, Vlan1817
C 181.0.8.0/24 is directly
connected, Vlan1818
L 181.0.8.1/32 is directly
connected, Vlan1818
C 181.0.9.0/24 is directly
connected, Vlan1819
L 181.0.9.1/32 is directly
connected, Vlan1819
B 200.0.1.0/24 [200/0] via
181.0.0.1, 00:04:04 (router
BGP-2 vía BGP-1)
B
200.0.2.0/24 [200/0] via 181.0.0.1, 00:04:04
B
200.0.3.0/24 [200/0] via 181.0.0.1, 00:04:04
BGP-4#
Tenemos que entender que si enviáramos tráfico desde
la red 181.0.7.0/24 a la red 181.0.4.0/24, este iría directamente desde
BGP-4 a BGP-3, sin pasar por BGP-1 tal como vimos
en la tabla de enrutamiento.
3.6.- Forzamos un update:
3.6.1.- Activamos el debug para observar los updates:
3.6.1.1.- En router BGP-4:
BGP-4#debug ip bgp updates
BGP updates debugging is on for address family: IPv4 Unicast
BGP-4#debug ip routing
IP routing debugging is on
BGP-4#
3.6.1.2.- En router BGP-1:
BGP-1#debug ip bgp updates
BGP updates debugging is on for address family: IPv4 Unicast
BGP-1#
3.6.2.- Bajamos la red
181.0.4.0/24 en BGP-3:
BGP-3#conf t
Enter configuration commands, one per line. End with CNTL/Z.
BGP-3(config)#int vlan 1814
BGP-3(config-if)#shut
BGP-3(config-if)#
3.6.3.- Verificamos en
BGP-4:
BGP-4#
May 18 18:41:38.131: BGP(0):
181.0.0.1 rcv UPDATE about
181.0.4.0/24 – withdrawn (la ruta de BGP-3 se anuncia desde BGP-1)
BGP: TX IPv4 Unicast Net global 181.0.4.0/24 Changed.
May 18 18:41:38.131: BGP(0): no valid path for 181.0.4.0/24
May 18 18:41:38.131: BGP(0): nettable_walker
181.0.4.0/24 no best path
May 18 18:41:38.131: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for
181.0.4.0/24
May 18 18:41:38.131: RT: del 181.0.4.0 via 181.0.0.2, bgp
metric [200/0]
May 18 18:41:38.131: RT: delete
subnet route to 181.0.4.0/24
BGP: TX IPv4 Unicast Net global 181.0.4.0/24 RIB done.
BGP: TX IPv4 Unicast Tab RIB walk done version 46, added 1 topologies.
BGP: TX IPv4 Unicast Tab Executing.
BGP: TX IPv4 Unicast Wkr global 7 Cur
Processing.
BGP: TX IPv4 Unicast Top global Appending nets from attr
0x85E75CC4.
BGP: TX IPv4 Unicast Wkr global 7 Cur Attr change from 0x0 to 0x85E75CC4.
BGP: TX IPv4 Unicast Wkr global 7 Cur Net
181.0.4.0/24 Skipped.
BGP: TX IPv4 Unicast Top global No attributes with modified nets.
BGP: TX IPv4 Unicast Top global Added tail marker with version 46.
BGP: TX IPv4 Unicast Wkr global 7 Cur Reached
marker with version 46.
BGP: TX IPv4 Unicast Top global No attributes with modified nets.
BGP: TX IPv4 Unicast Wkr global 7 Cur Done (end
of list), processed 1 attr(s), 0/1 net(s), 0 pos.
BGP: TX IPv4 Unicast Grp global 7 Converged.
BGP: TX IPv4 Unicast Tab Processed 1 walker(s).
BGP: TX IPv4 Unicast Tab Generation completed.
BGP: TX IPv4 Unicast Top global Deleting first marker with version 45.
BGP: TX IPv4 Unicast Top global Collection reached marker 45 after 0
net(s).
BGP: TX IPv4 Unicast Top global Collection done on marker 46 after 1
net(s).
BGP: TX IPv4 Unicast Top global Collection done on marker 46 after 0
net(s).
BGP: TX IPv4 Unicast Tab RIB walk done version 46, added 1 topologies.
May 18 18:42:25.907: BGP: TX Member message pool below threshold (0 <
0).
BGP-4#
BGP-4#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, 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
i
- IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 -
IS-IS level-2
ia
- IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic
downloaded static route, + - replicated route
Gateway of last resort is not set
181.0.0.0/16 is variably subnetted, 13 subnets, 2 masks
C 181.0.0.0/24 is directly
connected, Vlan1810 (backbone
BGP)
L 181.0.0.3/32 is directly
connected, Vlan1810
B 181.0.1.0/24 [200/0] via
181.0.0.1, 00:49:53 (router
BGP-1)
B
181.0.2.0/24 [200/0] via 181.0.0.1, 00:49:53
B
181.0.3.0/24 [200/0] via
181.0.0.1, 00:49:53
B
181.0.5.0/24 [200/0] via
181.0.0.2, 00:49:53 (router BGP-3)(no existe
181.0.4.0/24)
B 181.0.6.0/24 [200/0] via 181.0.0.2, 00:49:53
C 181.0.7.0/24 is directly
connected, Vlan1817 (redes
locales)
L 181.0.7.1/32 is directly
connected, Vlan1817
C 181.0.8.0/24 is directly
connected, Vlan1818
L 181.0.8.1/32 is directly
connected, Vlan1818
C 181.0.9.0/24 is directly
connected, Vlan1819
L 181.0.9.1/32 is directly
connected, Vlan1819
B 200.0.1.0/24 [200/0] via
181.0.0.1, 00:49:55 (router
BGP-2 vía BGP-1)
B
200.0.2.0/24 [200/0] via 181.0.0.1, 00:49:55
B
200.0.3.0/24 [200/0] via 181.0.0.1, 00:49:55
BGP-4#
3.6.4.- Verificamos en
BGP-1:
BGP-1#
May 18 19:53:08.019: BGP(0): 181.0.0.2 rcv
UPDATE about 181.0.4.0/24 --
withdrawn
May 18 19:53:08.019: BGP(0): no valid path for
181.0.4.0/24
May 18 19:53:08.019: BGP(0): nettable_walker
181.0.4.0/24 no best path
May 18 19:53:08.019: BGP(0): 181.0.0.2 send
unreachable 181.0.4.0/24
May 18 19:53:08.019: BGP(0): 181.0.0.2 send
UPDATE 181.0.4.0/24 -- unreachable
May 18 19:53:08.019: BGP(0): 190.0.0.2 send
unreachable 181.0.4.0/24
May 18 19:53:08.019: BGP(0): 190.0.0.2 send
UPDATE 181.0.4.0/24 -- unreachable
May 18 19:53:08.119: BGP(0): updgrp
2 - 181.0.0.2 updates replicated
for neighbors: 181.0.0.3
BGP-1#
3.6.5.- Levantamos la red
181.0.4.0/24 en BGP-3:
BGP-3(config)#int vlan 1814
BGP-3(config-if)#no shut
BGP-3(config-if)#
3.6.6.- Verificamos en
BGP-4:
May 18 18:43:23.495: BGP(0): 181.0.0.1 rcvd
UPDATE w/ attr: nexthop
181.0.0.2, origin i, localpref 100, metric 0, originator 181.0.0.2, clusterlist
181.0.0.1
May 18 18:43:23.495: BGP(0): 181.0.0.1 rcvd 181.0.4.0/24
BGP: TX IPv4 Unicast Net global 181.0.4.0/24 Changed.
May 18 18:43:23.495: BGP(0): Revise route
installing 1 of 1 routes for 181.0.4.0/24 -> 181.0.0.2(global) to main IP
table
May 18 18:43:23.495: RT: updating bgp
181.0.4.0/24 (0x0) via 181.0.0.2
May 18 18:43:23.495: RT: add
181.0.4.0/24 via 181.0.0.2, bgp metric [200/0]
BGP: TX IPv4 Unicast Net global 181.0.4.0/24 RIB done.
BGP: TX IPv4 Unicast Tab RIB walk done version 47, added 1 topologies.
BGP: TX IPv4 Unicast Tab Executing.
BGP: TX IPv4 Unicast Wkr global 7 Cur
Processing.
BGP: TX IPv4 Unicast Top global Appending nets from attr
0x861E5F84.
BGP: TX IPv4 Unicast Wkr global 7 Cur Attr change from 0x0 to 0x861E5F84.
BGP: TX IPv4 Unicast Wkr global 7 Cur Net
181.0.4.0/24 Skipped.
BGP: TX IPv4 Unicast Top global No attributes with modified nets.
BGP: TX IPv4 Unicast Top global Added tail marker with version 47.
BGP: TX IPv4 Unicast Wkr global 7 Cur Reached
marker with version 47.
BGP: TX IPv4 Unicast Top global No attributes with modified nets.
BGP: TX IPv4 Unicast Wkr global 7 Cur Done (end
of list), processed 1 attr(s), 0/1 net(s), 0 pos.
BGP: TX IPv4 Unicast Grp global 7 Converged.
BGP: TX IPv4 Unicast Tab Processed 1 walker(s).
BGP: TX IPv4 Unicast Tab Generation completed.
BGP: TX IPv4 Unicast Top global Deleting first marker with version 46.
BGP: TX IPv4 Unicast Top global Collection reached marker 46 after 0
net(s).
BGP: TX IPv4 Unicast Top global Collection done on marker 47 after 1
net(s).
BGP: TX IPv4 Unicast Top global Collection done on marker 47 after 0
net(s).
May 18 18:43:26.347: BGP: TX Member message pool below threshold (0 <
0).
BGP: TX IPv4 Unicast Tab RIB walk done version 47, added 1 topologies.
BGP-4#
3.6.7.- Verificamos en
BGP-1:
BGP-1#
May 18 19:55:37.959: BGP(0): 181.0.0.2 rcvd UPDATE w/ attr: nexthop 181.0.0.2, origin i, localpref 100, metric 0
May 18 19:55:37.959: BGP(0): 181.0.0.2 rcvd 181.0.4.0/24
May 18 19:55:37.963: BGP(0): Revise route
installing 1 of 1 routes for 181.0.4.0/24 -> 181.0.0.2(main) to main IP
table
May 18 19:55:37.963: BGP(0): 181.0.0.2 send
UPDATE (format) 181.0.4.0/24, next 181.0.0.2, metric 0, path Local
May 18 19:55:37.963: BGP(0): 190.0.0.2 send
UPDATE (format) 181.0.4.0/24, next 190.0.0.1, metric 0, path Local
May 18 19:55:38.063: BGP(0): updgrp
2 - 181.0.0.2 updates replicated
for neighbors: 181.0.0.3
BGP-1#
(2023) Tales for insane people
Rosario, Argentina