BGP and EIGRP redistribution question

Routing & Switching BGP
1

Hi Everyone,

On my production router, I have this setup:

prod_router#sh run | Sec router
router eigrp PROD
 !
 address-family ipv4 unicast autonomous-system 101
  !
  topology base
   redistribute connected
   redistribute static metric 10000 10 255 255 150 route-map static-to-eigrp
   redistribute bgp 65001 metric 100 1 255 1 1500
  exit-af-topology
  network 10.19.3.0 0.0.0.255
 exit-address-family
 !

router bgp 65001
 bgp log-neighbor-changes
 neighbor 192.65.0.13 remote-as 3549
 neighbor 192.65.0.13 version 4
 neighbor 192.65.0.13 timers 5 15
 !
 address-family ipv4
  network 10.19.3.0 mask 255.255.255.0
  redistribute eigrp 101 metric 100 route-map eigrp-to-bgp
  neighbor 192.65.0.13 activate
  neighbor 192.65.0.13 next-hop-self
 exit-address-family
 !
prod_router#sh run | sec ip route
ip route 172.16.5.0 255.255.255.0 172.19.3.1 200
ip route 172.16.6.0 255.255.255.0 172.19.3.1 200
prod_router#

route-map static-to-eigrp permit 10
 match ip address static-to-eigrp

route-map eigrp-to-bgp permit 10
 match ip address eigrp-to-bgp

ip access-list standard static-to-eigrp
 10 deny   any

ip access-list extended eigrp-to-bgp
 10 permit ip 10.19.3.0 0.0.0.255 any
 20 permit ip any any

I have a couple questions:

  1. What are these lines exactly meant? please explain in a plain English if possible!
       redistribute static metric 10000 10 255 255 150 route-map static-to-eigrp
       redistribute bgp 65001 metric 100 1 255 1 1500
       redistribute eigrp 101 metric 100 route-map eigrp-to-bgp
  1. Regarding route-map of ‘redistribute static metric 10000 10 255 255 150 route-map static-to-eigrp’.
       route-map static-to-eigrp permit 10
             match ip address static-to-eigrp
       ip access-list standard static-to-eigrp
             10 deny   any

If the ‘static-to-eigrp’ ACL is denying all, why do we need to redistribute static in to eigrp?

Thanks!

2

Hello Tom

This command redistributes all static routes into EIGRP using the indicated EIGRP metrics. Only those static routes that match the static-to-eigrp route map will be redistributed.

This command redistributes all BGP routes learned from AS65001 into EIGRP with the indicated EIGRP metrics. There is no route map indicated here, so all routes are redistributed.

This command, found under the BGP configuration, redistributes all EIGRP routes into BGP that match the route map eigrp-to-bgp. Based on the route map, everything is matched, so there is no restriction.

Indeed the route map is not matching anything therefore no redistribution is being achieved. Now it is not unusual to find such a configuration. This is typically done when network admins need to change routing occasionally. They create the redistribution, and the route map, but keep the ACL as “deny any”. Whenever you want to redistribute specific static routes, you only need to change the ACL. If you want to stop redistributing, just put deny any in the ACL again, and you’ve removed redistribution. That way, the config is there, and it can easily be adjusted by simply adjusting the ACL.

I hope this has been helpful!

Laz