14-5 redistribute routing-process process-id tag tag-value

14-5 redistribute routing-process process-id tag tag-value

Syntax Description:

• routing-process ” Routing process to redistribute into OSPF. The routing process can be BGP, Connected, EGP, EIGRP, IGRP, ISIS, ISO-IGRP, Mobile, ODR, OSPF, RIP, or Static.

• process-id ” The process ID of the routing process (if applicable ).

• ospf-metric ” The metric or cost to assign to the redistributed routes. If this option is not used, a default metric of 1 will be used for redistributed BGP routes and a default metric of 20 will be used for all other protocols. The range of values is 0 “16,777,214.

• metric-type ” Routes are redistributed into OSPF as either type 1 or type 2 routes. The default is type 2.

• tag-value ” A 32-bit value that is attached to the redistributed routes. The route tag is not used by OSPF but can be referenced in a route map for making policy decisions. One possible use is to base the decision to redistribute a route based on the route tag (see Section 14-6). The default tag value is 0. The range of values for the tag is 0 “4,294,967,295.

Purpose: To redistribute routes learned from another routing process into OSPF. Redis-tributed routes become OSPF external type 2 routes by default. The default cost or metric of a redistributed route is 1 for BGP and 20 for all other protocols. This command will redistribute classful routes into OSPF only if the subnets keyword is not used. There are three general types of classful routes:

• A Class A address with an 8-bit subnet mask

• A Class B address with a 16-bit subnet mask

• A Class C address with a 24-bit subnet mask

Initial Cisco IOS Software Release: 10.0

Configuration Example: 1 Redistributing Classful Routes into OSPF with the Default Type and Metric

In Figure 14-1, Router B is receiving six routes from Router C via EIGRP. Three of the EIGRP routes are classful (5.0.0.0/8, 145.5.0.0/16, 205.5.5.0/24) and three are classless (6.0.0.0/12, 146.6.0.0/20, 206.6.6.0/28). Before redistributing the EIGRP routes into OSPF on Router B, configure the routers as shown in the listing that follows .

Figure 14-1. By Default, OSPF Will Redistribute Only Classful Routes

 Router A  interface Loopback0   ip address 1.1.1.1 255.255.255.255   !   interface Serial0/1   ip address 10.1.1.1 255.255.255.252   clockrate 64000   !   router ospf 1   network 10.1.1.0 0.0.0.3 area 0  _______________________________________________________________________ Router B  interface Loopback0   ip address 2.2.2.2 255.255.255.255   !   interface Serial0   ip address 10.1.1.2 255.255.255.252   !   interface Serial 1   ip address 10.1.1.5 255.255.255.252   !   router eigrp 1   network 10.0.0.0   !   router ospf 1   network 10.1.1.0 0.0.0.3 area 0  _______________________________________________________________________ Router C  interface Loopback0   ip address 3.3.3.3 255.255.255.255   !   interface Loopback1   ip address 5.5.5.5 255.0.0.0   !   interface Loopback2   ip address 6.6.6.6 255.240.0.0   !   interface Loopback3   ip address 145.5.5.5 255.255.0.0   !   interface Loopback4   ip address 146.6.6.6 255.255.240.0   !   interface Loopback5   ip address 205.5.5.5 255.255.255.0   !   interface Loopback6   ip address 206.6.6.6 255.255.255.240   !   interface Serial0   ip address 10.1.1.6 255.255.255.252   !   router eigrp 1   network 5.0.0.0   network 6.0.0.0   network 10.0.0.0   network 145.5.0.0   network 146.6.0.0   network 205.5.5.0   network 206.6.6.0   no auto-summary  

Verify that Routers A and B have established an OSPF neighbor relationship.

 rtrA#  show ip ospf neighbor  Neighbor ID     Pri   State           Dead Time   Address         Interface 2.2.2.2           1  FULL/  -  00:00:36    10.1.1.2        Serial0/1 

Verify that Routers B and C have formed an EIGRP neighbor relationship.

 rtrB#  show ip eigrp neighbors  IP-EIGRP neighbors for process 1 H   Address                 Interface   Hold  Uptime  SRTT   RTO  Q  Seq                                         (sec)         (ms)       Cnt Num 0   10.1.1.6                Se1           11  00:25:42  308  2280  0  4 

Verify that Router B is receiving the six EIGRP routes from Router C.

 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  D    205.5.5.0/24 [90/40640000] via 10.1.1.6, 00:26:25, Serial1  206.6.6.0/28 is subnetted, 1 subnets  D       206.6.6.0 [90/40640000] via 10.1.1.6, 00:26:25, Serial1   D    5.0.0.0/8 [90/40640000] via 10.1.1.6, 00:26:25, Serial1  6.0.0.0/12 is subnetted, 1 subnets  D       6.0.0.0 [90/40640000] via 10.1.1.6, 00:26:25, Serial1   D    145.5.0.0/16 [90/40640000] via 10.1.1.6, 00:26:25, Serial1  10.0.0.0/30 is subnetted, 2 subnets C       10.1.1.0 is directly connected, Serial0 C       10.1.1.4 is directly connected, Serial1      146.6.0.0/20 is subnetted, 1 subnets  D       146.6.0.0 [90/40640000] via 10.1.1.6, 00:26:27, Serial1  

Modify the configuration on Router B to redistribute the classful EIGRP routes into OSPF.

  router ospf 1    redistribute eigrp 1   

When the command redistribute eigrp 1 is entered, the router will give you the following friendly reminder:

 rtrB(config-router)#  redistribute eigrp 1  % Only classful networks will be redistributed 

Verification

Determine the routes that have been redistributed by examining the IP routing table on Router A.

 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  O E2 205.5.5.0/24 [110/20] via 10.1.1.2, 00:33:23, Serial0/1   O E2 5.0.0.0/8 [110/20] via 10.1.1.2, 00:33:23, Serial0/1   O E2 145.5.0.0/16 [110/20] via 10.1.1.2, 00:33:23, Serial0/1  10.0.0.0/30 is subnetted, 1 subnets C       10.1.1.0 is directly connected, Serial0/1 

Only the EIGRP classful routes were redistributed into OSPF. As you can see in the routing table on Router A, EIGRP routes were redistributed as external type 2 with a cost or metric of 20. This information can also be found by inspecting 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: 410   Options: (No TOS-capability, DC)  LS Type: AS External Link   Link State ID: 5.0.0.0 (External Network Number )  Advertising Router: 2.2.2.2   LS Seq Number: 80000004   Checksum: 0x642C   Length: 36  Network Mask: /8   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: 419   Options: (No TOS-capability, DC)  LS Type: AS External Link   Link State ID: 145.5.0.0 (External Network Number )  Advertising Router: 2.2.2.2   LS Seq Number: 80000004   Checksum: 0x5F9   Length: 36  Network Mask: /16   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: 435   Options: (No TOS-capability, DC)  LS Type: AS External Link   Link State ID: 205.5.5.0 (External Network Number )  Advertising Router: 2.2.2.2   LS Seq Number: 80000004   Checksum: 0xBEFE   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 

Configuration Example: 2 Redistributing Classful Routes into OSPF with the Default Type and Specific Metric

In the first configuration example for Figure 14-1, the EIGRP routes were redistributed into OSPF with a default metric of 20. For this example, modify the configuration on Router B to change the metric of all the redistributed EIGRP routes to 66.

 Router B  router ospf 1     redistribute eigrp 1 metric 66   

Verification

Verify that the new metric has been applied to the redistributed EIGRP routes. On Router A you can look at the IP routing table and on Router B you can inspect the OSPF database.

 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  O E2 205.5.5.0/24 [110/66] via 10.1.1.2, 00:00:16, Serial0/1   O E2 5.0.0.0/8 [110/66] via 10.1.1.2, 00:00:16, Serial0/1   O E2 145.5.0.0/16 [110/66] via 10.1.1.2, 00:00:16, Serial0/1  10.0.0.0/30 is subnetted, 1 subnets C       10.1.1.0 is directly connected, Serial0/1 

Configuration Example: 3 Redistributing Classful Routes into OSPF as Type 1 Routes Using a Specific Metric

Routes are redistributed in OSPF as either type 1 (E1) routes or type 2 (E2) routes, with type 2 being the default. A type 1 route has a metric that is the sum of the internal OSPF cost and the external redistributed cost. A type 2 route has a metric equal only to the redistributed cost, as shown in Figure 14-2. If routes are redistributed into OSPF as type 2 then every router in the OSPF domain will see the same cost to reach the external networks. If routes are redistributed into OSPF as type 1, then the cost to reach the external networks could vary from router to router.

Figure 14-2. OSPF Routes Are Redistributed as Either Type 1 or Type 2 Routes

Modify the configuration on Router B so that the EIGRP routes are redistributed as type 1 routes.

 Router B  router ospf 1     redistribute eigrp 1 metric 66 metric-type 1   

Verification

Verify that the EIGRP routes have been redistributed into OSPF as type 1 routes with a metric of 66.

 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: 149   Options: (No TOS-capability, DC)   LS Type: AS External Link  Link State ID: 5.0.0.0 (External Network Number )  Advertising Router: 2.2.2.2   LS Seq Number: 80000008   Checksum: 0xA638   Length: 36   Network Mask: /8  Metric Type: 1 (Comparable directly to link state metric)  TOS: 0  Metric: 66  Forward Address: 0.0.0.0         External Route Tag: 0   LS age: 158   Options: (No TOS-capability, DC)   LS Type: AS External Link  Link State ID: 145.5.0.0 (External Network Number )  Advertising Router: 2.2.2.2   LS Seq Number: 80000008   Checksum: 0x4706   Length: 36   Network Mask: /16  Metric Type: 1 (Comparable directly to link state metric)  TOS: 0  Metric: 66  Forward Address: 0.0.0.0         External Route Tag: 0   LS age: 168   Options: (No TOS-capability, DC)   LS Type: AS External Link  Link State ID: 205.5.5.0 (External Network Number )  Advertising Router: 2.2.2.2   LS Seq Number: 80000008   Checksum: 0x10B   Length: 36   Network Mask: /24  Metric Type: 1 (Comparable directly to link state metric)  TOS: 0  Metric: 66  Forward Address: 0.0.0.0         External Route Tag: 0 

Verify that the cost of these routes as seen by Router A is the sum of the redistributed metric and the OSPF cost to reach 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  O E1 205.5.5.0/24 [110/1628]  via 10.1.1.2, 00:05:36, Serial0/1  O E1 5.0.0.0/8 [110/1628]  via 10.1.1.2, 00:05:36, Serial0/1  O E1 145.5.0.0/16 [110/1628]  via 10.1.1.2, 00:05:36, Serial0/1      10.0.0.0/30 is subnetted, 1 subnets C       10.1.1.0 is directly connected, Serial0/1 

Configuration Example: 4 Redistributing Subnet Routes into OSPF as Type 1 Routes Using a Specific Metric

The previous configuration examples redistributed only the classful EIGRP routes into OSPF. Modify the configuration on Router B to redistribute all the EIGRP routes.

 Router B  router ospf 1     redistribute eigrp 1 metric 66 metric-type 1 subnets   

Verification

Verify that the classless EIGRP routes have been redistributed into OSPF on Router B by inspecting the IP routing table on Router A.

 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 O E1 205.5.5.0/24 [110/1628] via 10.1.1.2, 00:22:36, Serial0/1  206.6.6.0/28 is subnetted, 1 subnets   O E1    206.6.6.0 [110/1628] via 10.1.1.2, 00:02:37, Serial0/1  O E1 5.0.0.0/8 [110/1628] via 10.1.1.2, 00:22:36, Serial0/1  6.0.0.0/12 is subnetted, 1 subnets   O E1    6.0.0.0 [110/1628] via 10.1.1.2, 00:02:37, Serial0/1  O E1 145.5.0.0/16 [110/1628] via 10.1.1.2, 00:22:37, Serial0/1      10.0.0.0/30 is subnetted, 2 subnets C       10.1.1.0 is directly connected, Serial0/1 O E1    10.1.1.4 [110/1628] via 10.1.1.2, 00:02:40, Serial0/1  146.6.0.0/20 is subnetted, 1 subnets   O E1    6.0.0.0 [110/1628] via 10.1.1.2, 00:02:37, Serial0/1  

Configuration Example: 5 Redistributing Subnet Routes into OSPF as Type 1 Routes Using a Specific Metric and Route Tag

A route tag is a 32-bit value that is attached to the redistributed routes. Every route that is redistributed will be assigned the same route tag unless a route map is used (see Section 14-6). OSPF itself does not use the route tag, but you can use the tag value to implement policy decisions. For example, in Section 14-6, the tag value is used to determine which routes will be redistributed into OSPF based on their tag values. This example presents only the mechanics of assigning the tag. Modify the configuration on Router B to redistribute the EIGRP routes with a tag value of 555.

 Router B  router ospf 1     redistribute eigrp 1 metric 66 metric-type 1 subnets tag 555   

Verification

The tag value can be verified by examining a particular route in the IP routing table on Router A.

 rtrA#  show ip route 5.0.0.0  Routing entry for 5.0.0.0/8   Known via "ospf 1", distance 110, metric 1628  Tag 555  , type extern 1   Last update from 10.1.1.2 on Serial0/1, 00:03:57 ago   Routing Descriptor Blocks:   * 10.1.1.2, from 2.2.2.2, 00:03:57 ago, via Serial0/1       Route metric is 1628, traffic share count is 1 

The tag value can also be verified by inspecting the external routes in the OSPF database on either Router A or B.

 rtrA#  show ip ospf database external 5.0.0.0  OSPF Router with ID (1.1.1.1) (Process ID 1)                 Type-5 AS External Link States   Routing Bit Set on this LSA   LS age: 313   Options: (No TOS-capability, DC)   LS Type: AS External Link   Link State ID: 5.0.0.0 (External Network Number )   Advertising Router: 2.2.2.2   LS Seq Number: 8000002A   Checksum: 0x8D02   Length: 36   Network Mask: /8         Metric Type: 1 (Comparable directly to link state metric)         TOS: 0         Metric: 66         Forward Address: 0.0.0.0  External Route Tag: 555  _______________________________________________________________________ rtrB#  show ip ospf database external 145.5.0.0  OSPF Router with ID (2.2.2.2) (Process ID 1)                 Type-5 AS External Link States   LS age: 373   Options: (No TOS-capability, DC)   LS Type: AS External Link   Link State ID: 145.5.0.0 (External Network Number )   Advertising Router: 2.2.2.2   LS Seq Number: 8000002A   Checksum: 0x2ECF   Length: 36   Network Mask: /16         Metric Type: 1 (Comparable directly to link state metric)         TOS: 0         Metric: 66         Forward Address: 0.0.0.0  External Route Tag: 555  

Troubleshooting

Verify that there is a neighbor relationship between the OSPF routers by using the show ip ospf neighbors command.

Step 1. Verify that the redistribute command is referencing the correct routing process and process number (if applicable).

Step 2. Remember the defaults: metric = 20 (1 for BGP), metric type = 2, tag = 0.

To avoid problems associated with mutual redistribution, either use a distribute list (see Sections 7-5, 7-10, and 7-15) or a route map (see Section 14-6) to allow only routes that originated in the routing process domain.

For example, if on the same router, EIGRP is redistributed into OSPF and OSPF is redistributed into EIGRP, then OSPF routes will be redistributed back into OSPF from EIGRP and EIGRP routes will be redistributed back into EIGRP from OSPF. Use a route map or distribute list to prevent this from occurring.