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7-10 distribute-list access-list- name out routing-processSyntax Description:
Purpose: To prevent routes, redistributed into OSPF from another routing rocess, from being installed in the OSPF database. Initial Cisco IOS Software Release: 11.2 Configuration Example: Preventing Routes Redistributed into OSPF from Being Installed in the OSPF DatabaseIn Figure 7-6, Router B is receiving the EIGRP routes 10.1.1.4/30, 3.3.3.0/24, and 4.4.4.0/24 from Router C. Router B is redistributing EIGRP into OSPF and these routes will be advertised to Router A as OSPF external type 2 routes. Start by configuring Routers A, B, and C as shown in the listing that follows the figure. Figure 7-6. A Distribute List/Named Access List Prevents Redistributed Routes from Being Installed in the OSPF Database
Router A interface Loopback0 ip address 1.1.1.1 255.255.255.255 ! interface Ethernet0/0 ip address 172.16.1.1 255.255.255.0 ! router ospf 1 network 172.16.1.0 0.0.0.255 area 0 ________________________________________________________________________________ Router B interface Loopback0 ip address 2.2.2.2 255.255.255.255 ! interface Ethernet0 ip address 172.16.1.2 255.255.255.0 ! interface Serial1 bandwidth 64 ip address 10.1.1.5 255.255.255.252 clockrate 64000 ! router eigrp 1 network 10.0.0.0 ! router ospf 1 redistribute eigrp 1 subnets network 2.2.2.2 0.0.0.0 area 1 network 172.16.1.0 0.0.0.255 area 0 ________________________________________________________________________________ Router C interface Loopback0 ip address 3.3.3.3 255.255.255.0 ! interface Loopback1 ip address 4.4.4.4 255.255.255.0 ! interface Serial0 ip address 10.1.1.6 255.255.255.252 ! router eigrp 1 network 3.0.0.0 network 4.0.0.0 network 10.0.0.0 no auto-summary Verify that Routers A and B have established a FULL OSPF neighbor relationship. rtrA# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 2.2.2.2 1 FULL/BDR 00:00:30 172.16.1.2 Ethernet0/0 rtrB# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 1.1.1.1 1 FULL/DR 00:00:38 172.16.1.1 Ethernet0 Verify that Router B is receiving routes 3.3.3.0/24 and 4.4.4.0/24 from Router C via EIGRP. rtrB# show ip route Codes: C - connected, S - static, I - IGRP, 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, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is not set 2.0.0.0/32 is subnetted, 1 subnets C 2.2.2.2 is directly connected, Loopback0 3.0.0.0/24 is subnetted, 1 subnets D 3.3.3.0 [90/40640000] via 10.1.1.6, 00:38:45, Serial1 4.0.0.0/24 is subnetted, 1 subnets D 4.4.4.0 [90/40640000] via 10.1.1.6, 00:38:45, Serial1 172.16.0.0/24 is subnetted, 1 subnets C 172.16.1.0 is directly connected, Ethernet0 10.0.0.0/30 is subnetted, 1 subnets C 10.1.1.4 is directly connected, Serial1 Verify that Router A is receiving routes 10.1.1.4/30, 3.3.3.0/24, and 4.4.4.0/24 from Router B as OSPF external type 2 routes. rtrA# show ip route Codes: C - connected, S - static, I - IGRP, 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 , E - EGP i - IS-IS, 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 1.0.0.0/32 is subnetted, 1 subnets C 1.1.1.1 is directly connected, Loopback0 2.0.0.0/32 is subnetted, 1 subnets O IA 2.2.2.2 [110/11] via 172.16.1.2, 00:27:48, Ethernet0/0 3.0.0.0/24 is subnetted, 1 subnets O E2 3.3.3.0 [110/20] via 172.16.1.2, 00:05:41, Ethernet0/0 4.0.0.0/24 is subnetted, 1 subnets O E2 4.4.4.0 [110/20] via 172.16.1.2, 00:27:48, Ethernet0/0 172.16.0.0/24 is subnetted, 1 subnets C 172.16.1.0 is directly connected, Ethernet0/0 10.0.0.0/30 is subnetted, 1 subnets O E2 10.1.1.4 [110/20] via 172.16.1.2, 00:05:42, Ethernet0/0 For illustrative purposes, verify that these three routes are in the OSPF database on Router B. rtrB# show ip ospf database external OSPF Router with ID (2.2.2.2) (Process ID 1) Type-5 AS External Link States LS age: 441 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 3.3.3.0 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0x3F50 Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 0.0.0.0 External Route Tag: 0 LS age: 1788 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 4.4.4.0 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000003 Checksum: 0x1773 Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 0.0.0.0 External Route Tag: 0 LS age: 459 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 10.1.1.4 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0xD7B3 Length: 36 Network Mask: /30 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 0.0.0.0 External Route Tag: 0 Modify the configuration on Router B to allow only the installation of the EIGRP route 4.4.4.0/24 into the OSPF database using a named access list. Router B router ospf 1 redistribute eigrp 1 subnets network 2.2.2.2 0.0.0.0 area 1 network 172.16.1.0 0.0.0.255 area 0 distribute-list filter-eigrp out eigrp 1 ! ip access-list standard filter-eigrp permit 4.4.4.0 0.0.0.255 VerificationVerify that the EIGRP routes 10.1.1.4/30 and 3.3.3.0/24 have been blocked from entering the OSPF database on Router B. rtrB# show ip ospf database external OSPF Router with ID (2.2.2.2) (Process ID 1) Type-5 AS External Link States LS age: 419 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 4.4.4.0 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000004 Checksum: 0x1574 Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 0.0.0.0 External Route Tag: 0 Verify that Router A is receiving only one external type 2 route from Router B. rtrA# show ip route Codes: C - connected, S - static, I - IGRP, 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, E - EGP i - IS-IS, 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 1.0.0.0/32 is subnetted, 1 subnets C 1.1.1.1 is directly connected, Loopback0 2.0.0.0/32 is subnetted, 1 subnets O IA 2.2.2.2 [110/11] via 172.16.1.2, 00:38:45, Ethernet0/0 4.0.0.0/24 is subnetted, 1 subnets O E2 4.4.4.0 [110/20] via 172.16.1.2, 00:38:45, Ethernet0/0 172.16.0.0/24 is subnetted, 1 subnets C 172.16.1.0 is directly connected, Ethernet0/0 Troubleshooting
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