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Route filtering passive interface
Cisco IOS provides several ways to control updates traffic. Passive interface, distribute list, prefix list route maps. In this section, we take look at the passive interface in RIPv2, EIGRP, and OSPF.
Passive interface command is used in al routing protocol to disable sending updates out from a specific interface. However, the command behavior varies from one protocol to another.
EIGRP Passive interface
EIGRP do not send any hello messages on passive interface. EIGRP router ignores any EIGRP messages received on the interface its means no neighbors relation but EIGRP still advertises about the connected subnet only if matched with an EIGRP network command.
lets see the configuration:-
Topology:
Goal:
configure the topology as per the diagram
configure EIGRP 65001 and advertise interface
configure router 3 interface serial 3/1 passive interface
make sure router 3 drop neighbourship and prevent routes
R2#show ip interface brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 20.1.1.1 YES manual up up
Serial3/0 1.1.1.2 YES manual up up
Serial3/1 2.1.1.1 YES manual up up
R3#show ip interface brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 30.1.1.1 YES manual up up
Serial3/1 2.1.1.2 YES manual up up
R1(config)#router eigrp 65001
R1(config-router)#network 1.0.0.0
R1(config-router)#network 10.0.0.0
R1(config-router)#exit
R2(config)#router eigrp 65001
R2(config-router)#network 20.0.0.0
R2(config-router)#network 2.0.0.0
R2(config-router)#network 1.0.0.0
*Mar 18 13:43:20.971: %DUAL-5-NBRCHANGE: EIGRP-IPv4 65001: Neighbor 1.1.1.1 (Serial3/0) is up: new adjacency
R2(config-router)#end
R3(config)#router eigrp 65001
R3(config-router)#network 2.0.0.0
*Mar 18 13:44:10.655: %DUAL-5-NBRCHANGE: EIGRP-IPv4 65001: Neighbor 2.1.1.1 (Serial3/1) is up: new adjacency
R3(config-router)#network 30.0.0.0
R3(config-router)#end
R1#show ip route eigrp
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
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 2.0.0.0/8 [90/2681856] via 1.1.1.2, 00:03:36, Serial3/0
D 20.0.0.0/8 [90/2172416] via 1.1.1.2, 00:03:36, Serial3/0
D 30.0.0.0/8 [90/2684416] via 1.1.1.2, 00:00:16, Serial3/0
R2#show ip route eigrp
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
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 10.0.0.0/8 [90/2172416] via 1.1.1.1, 00:04:00, Serial3/0
D 30.0.0.0/8 [90/2172416] via 2.1.1.2, 00:00:40, Serial3/1
R3#show ip route eigrp
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
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 1.0.0.0/8 [90/2681856] via 2.1.1.1, 00:00:58, Serial3/1
D 10.0.0.0/8 [90/2684416] via 2.1.1.1, 00:00:58, Serial3/1
D 20.0.0.0/8 [90/2172416] via 2.1.1.1, 00:00:58, Serial3/1
R2#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(65001)
H Address Interface Hold Uptime SRT RTO Q Seq (sec) (ms) Cnt Num
1 2.1.1.2 Se3/1 14 00:01:19 21 126 0 7
0 1.1.1.1 Se3/0 10 00:04:39 27 162 0 6
R2(config)#router eigrp 65001
R2(config-router)#passive-interface serial 3/1
*Mar 18 13:50:02.303: %DUAL-5-NBRCHANGE: EIGRP-IPv4 65001: Neighbor 2.1.1.2 (Serial3/1) is down: interface passive
R2(config-router)#end
R1#show ip route eigrp
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
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 2.0.0.0/8 [90/2681856] via 1.1.1.2, 00:07:22, Serial3/0
D 20.0.0.0/8 [90/2172416] via 1.1.1.2, 00:07:22, Serial3/0
R2#show ip route eigrp
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
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 10.0.0.0/8 [90/2172416] via 1.1.1.1, 00:07:56, Serial3/0
R2#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(65001)
H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num
0 1.1.1.1 Se3/0 13 00:08:29 32 192 0 7
