10-2 redistribute protocol metric metric

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10-2 redistribute protocol metric metric

Syntax Description:

  • protocol ” Routes learned via protocol will be redistributed into BGP.

  • metric ” Metric to assign to the redistributed routes. The value is in the range of 0 to 4294967295.

Purpose: To redistribute routes into BGP that have been learned via a routing protocol other than BGP. The metric value is assigned to the metric or multi-exit discriminator (MED) of the new BGP route. Routes can be redistributed from connected, dvmrp, egp, eigrp, igrp, isis, iso-igrp, mobile, odr, ospf, rip, and static.

Cisco IOS Software Release: 10.0

Configuration Example: Redistributing Connected, Static, and EIGRP Learned Routes into BGP

In Figure 10-2, Router C is advertising 172.16.2.0/24 and 172.16.3.0/24 to Router B via EIGRP. Routers A and B have an EBGP relationship. This example redistributes EIGRP and static into BGP on Router B and redistributes connected on Router A. The static routes are assigned a metric of 10, the EIGRP routes a metric of 15, and the connected routes a metric of 5.

Figure 10-2. Redistributing Routes into BGP

graphics/10fig02.gif

 Router A  interface loopback 0   ip address 172.16.0.1 255.255.255.0   !   interface loopback 1   ip address 172.16.1.1 255.255.255.0   !   router bgp 1   network 172.17.1.0 mask 255.255.255.0   neighbor 172.17.1.1 remote-as 2   ___________________________________________________________________________  Router B  router eigrp 1   network 10.0.0.0   network 172.17.0.0   no auto-summary   !   router bgp 2   network 10.1.0.0 mask 255.255.255.252   network 172.17.1.0 mask 255.255.255.0   neighbor 172.17.1.2 remote-as 1   !   ip route 172.16.4.0 255.255.255.0 s2/0   ___________________________________________________________________________  Router C  interface loopback 0   ip address 172.16.2.1 255.255.255.0   !   interface loopback 1   ip address 172.16.3.1 255.255.255.0   !   router eigrp 1   network 172.16.0.0   network 10.0.0.0   no auto-summary  

Before proceeding with the redistribution of routes into BGP, inspect the IP and BGP routing tables on Routers A and B. Router B should be learning routes 172.16.2.0/24 and 172.16.3.0/24 from Router C via EIGRP. Because you are not redistributing routes on Router B, Router A should not be learning about the 172.16.2.0/24 or 172.16.3.0/24 routes.

 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, 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      172.17.0.0/24 is subnetted, 1 subnets C       172.17.1.0 is directly connected, Ethernet0/0      172.16.0.0/24 is subnetted, 3 subnets S       172.16.4.0 is directly connected, Serial2/0  D       172.16.2.0 [90/1889792] via 10.1.1.2, 00:26:32, Serial2/0   D       172.16.3.0 [90/1889792] via 10.1.1.2, 00:26:32, Serial2/0  10.0.0.0/30 is subnetted, 1 subnets C       10.1.1.0 is directly connected, Serial2/0 rtrB#  show ip bgp  BGP table version is 3, local router ID is 172.17.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete    Network          Next Hop            Metric LocPrf Weight Path *> 10.1.1.0/30      0.0.0.0                  0         32768 i *  172.17.1.0/24    172.17.1.2               0             0 1 i *>                  0.0.0.0                  0         32768 i  ___________________________________________________________________________  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      172.17.0.0/24 is subnetted, 1 subnets C       172.17.1.0 is directly connected, FastEthernet0      172.16.0.0/24 is subnetted, 2 subnets C       172.16.0.0 is directly connected, Loopback0 C       172.16.1.0 is directly connected, Loopback1      10.0.0.0/30 is subnetted, 1 subnets B       10.1.1.0 [20/0] via 172.17.1.1, 00:25:38 rtrA#  show ip bgp  BGP table version is 4, local router ID is 172.16.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete    Network          Next Hop            Metric LocPrf Weight Path *> 10.1.1.0/30      172.17.1.1               0             0 2 i *> 172.17.1.0/24    0.0.0.0                  0         32768 i *                   172.17.1.1               0             0 2 i 

Notice that the metric for the EIGRP learned routes on Router B is 1889792. The form of the redistribute command that you will use does not use the metric of the route that is being redistributed but assigns one statically. Now modify the BGP configuration on Router B to enable the redistribution of the EIGRP and static routes into BGP. Also modify the configuration on Router A to enable the redistribution of connected routes.

 Router A  router bgp 1   network 172.17.1.0 mask 255.255.255.0    redistribute connected metric 5    neighbor 172.17.1.1 remote-as 2   ___________________________________________________________________________  Router B  router bgp 1   network 10.1.0.0 mask 255.255.255.0   network 172.17.1.0 mask 255.255.255.0    redistribute static metric 10     redistribute eigrp 1 metric 15    neighbor 172.17.1.2 remote-as 2  
Verification

Verify that the connected routes are being redistributed in BGP on Router A and that the static and EIGRP routes are being redistributed on Router B.

 rtrA#  show ip bgp  BGP table version is 15, local router ID is 172.16.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete    Network          Next Hop            Metric LocPrf Weight Path *> 10.0.0.0         172.17.1.1               0             0 2 ? *> 10.1.1.0/30      172.17.1.1               0             0 2 i  *  172.16.0.0       172.17.1.1              10             0 2 ?   *>                  0.0.0.0                  5         32768 ?  *> 172.17.0.0       0.0.0.0                  5         32768 ? *  172.17.1.0/24    172.17.1.1               0             0 2 i *>                  0.0.0.0                  5         32768 i  ___________________________________________________________________________  rtrB#  show ip bgp  BGP table version is 8, local router ID is 172.17.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete    Network          Next Hop            Metric LocPrf Weight Path *> 10.0.0.0         0.0.0.0                  0         32768 ? *> 10.1.1.0/30      0.0.0.0                  0         32768 i  *> 172.16.0.0       0.0.0.0                 10         32768 ?   *                   172.17.1.2               5             0 1 ?  *> 172.17.0.0       172.17.1.2               5             0 1 ? *> 172.17.1.0/24    0.0.0.0                  0         32768 i *                   172.17.1.2               5             0 1 i 

Why is the mask for the 172.16.x.x routes /16 (the entire Class B address 172.16.x.x)? By default, BGP summarizes redistributed routes on a classful boundary (see Chapter 2). Routers A and B now indicate that they can reach the entire Class B address block 172.16.x.x. Typically, this is not the behavior you want. When redistributing routes into BGP, it is a good idea to turn off auto-summarization. Modify the BGP configuration on Routers A and B to do this. Notice that Router A also summarizes the 10.0.0.0 and 172.17.0.0 networks because they are also directly connected.

 Router A  router bgp 1   network 172.17.1.0 mask 255.255.255.0   redistribute connected 5   neighbor 172.17.1.1 remote-as 2    no auto-summary    ___________________________________________________________________________  Router B  router bgp 1   network 10.1.0.0 mask 255.255.255.252   network 172.17.1.0 mask 255.255.255.0   redistribute static 10   redistribute eigrp 1 15   neighbor 172.17.1.2 remote-as 2    no auto-summary   

Reinspect the BGP tables on Routers A and B:

 rtrA#  show ip bgp  BGP table version is 9, local router ID is 172.16.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete    Network          Next Hop            Metric LocPrf Weight Path *> 10.1.1.0/30      172.17.1.1               0             0 2 i *> 172.16.0.0/24    0.0.0.0                  5         32768 ? *> 172.16.1.0/24    0.0.0.0                  5         32768 ? *> 172.16.2.0/24    172.17.1.1              15             0 2 ? *> 172.16.3.0/24    172.17.1.1              15             0 2 ? *> 172.16.4.0/24    172.17.1.1              10             0 2 ? *> 172.17.1.0/24    0.0.0.0                  5         32768 i *                   172.17.1.1               0             0 2 i  ___________________________________________________________________________  rtrB#  show ip bgp  BGP table version is 20, local router ID is 172.17.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete    Network          Next Hop            Metric LocPrf Weight Path *> 10.1.1.0/30      0.0.0.0                  0         32768 i *> 172.16.0.0/24    172.17.1.2               5             0 1 ? *> 172.16.1.0/24    172.17.1.2               5             0 1 ? *> 172.16.2.0/24    10.1.1.2                15         32768 ? *> 172.16.3.0/24    10.1.1.2                15         32768 ? *> 172.16.4.0/24    0.0.0.0                 10         32768 ? *  172.17.1.0/24    172.17.1.2               5             0 1 i *>                  0.0.0.0                  0         32768 i 
Troubleshooting
Step 1. Verify that the BGP neighbors are in the Established state using the show ip bgp neighbors command.

If the neighbor relationship is not in the Established state, see section 8-23.

Step 2. Verify that the protocol you are redistributing routes from is active on the router.

Step 3. When redistributing from a protocol that requires a process ID, verify that you are using the proper process ID in the redistribute command.

Step 4. Use the no auto-summary command under router BGP when redistributing routes into BGP.

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Cisco[r] BGP-4 Command and Configuration Handbook
Cisco BGP-4 Command and Configuration Handbook
ISBN: 1587055732
EAN: 2147483647
Year: 2001
Pages: 300

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