05-24-2007 12:32 AM - edited 03-03-2019 05:07 PM
hi guys,
How can i limit my redistribution from eigrp to BGP to only /24 networks? when i redistribute eigrp routes to bgp, /32 and /30 networks are also advertise unto bgp. i don't want this to happen, just want only /24 to be advertise by bgp. Doing some lab scenario.
CRtr<->EIGRP<->GWRtr<-BGP->ISP
tnx.
jeff
05-24-2007 12:34 AM
Hi,
Use a route-map when doing redistribution to filter unwanted routes, or just permit desired routes.
HTH, please do rate all helpful replies,
Mohammed Mahmoud.
05-24-2007 01:08 AM
Hi Mohammed,
Where will i put my filter? I tried putting it under bgp process but still advertises my /30 networks to my ebgp peer.
router bgp 100
redistribute eigrp 10 metric 0 route-map FILTER
FILTER - /24 networks
tia.
05-24-2007 01:36 AM
Hi,
Yes, you are placing it correctly, but what is the configuration under the route-map Filter ?
BR,
Mohammed Mahmoud.
05-24-2007 02:52 AM
Hi,
Here's the configuration im trying to simulate.
RouterC ---EIGRP RouterA --- BGP ISP
Router C
interface Serial0/0
ip address 10.10.10.2 255.255.255.252
clock rate 128000
no fair-queue
router eigrp 10
redistribute static
network 10.10.10.0 0.0.0.255
network 10.10.20.0 0.0.0.255
distribute-list 1 out
no auto-summary
!
ip route 10.10.30.0 255.255.255.0 Null0
ip route 10.10.40.0 255.255.255.0 Null0
ip route 10.10.50.0 255.255.255.0 Null0
!
RouterA
interface Serial2/0
ip address 100.100.100.2 255.255.255.252
!
interface Serial2/1
ip address 10.10.10.1 255.255.255.252
router bgp 100
no synchronization
bgp log-neighbor-changes
redistribute eigrp 10 metric 10 route-map OUT
neighbor 100.100.100.1 remote-as 200
neighbor 100.100.100.1 route-map OUT out
no auto-summary
!
no ip http server
ip classless
ip route 10.10.10.0 255.255.255.0 Null0
!
!
access-list 1 permit 10.10.20.0 0.0.0.255
access-list 1 permit 10.10.30.0 0.0.0.255
access-list 1 permit 10.10.40.0 0.0.0.255
access-list 1 permit 10.10.50.0 0.0.0.255
access-list 1 permit 10.10.10.0 0.0.0.255
route-map OUT permit 10
match ip address 1
I even put route-map on my bgp advertisement but still i can see /30.
Tnx.
05-24-2007 03:08 AM
Hi,
I would strongly recomend that when configuring BGP in this way you should use prefix lists instead :)
neighbor 20.20.20.20 prefix-list ABC out
ip prefix-list ABC seq 5 permit x.x.x.x/0
Please check the scroll-down box at the bottom rigth on every helpfull post :)
BR,
Bjornarsb
05-24-2007 03:10 AM
Hi,
Ok, here it is the problem, the standard access list looks at the network address only and can not check the length of the network mask in this scenario.
Here you are an example from one of the Cisco CCO documents:
To permit only the supernet 10.10.0.0/19, use an extended access list, such as access-list 101 permit ip 10.10.0.0 0.0.0.0 255.255.224.0 0.0.0.0.
Accordingly you'll have to use extended ACL in this manner or use prefix-lists which i would recommend.
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00801310cb.shtml
HTH, please do rate all helpful replies using the scroll box on the right,
Mohammed Mahmoud.
05-24-2007 03:10 AM
So to your case, depending on how you have configured acl 1 on router C,
you will still see /30 on router A
because /30 is more spesific than /24.
BR,
Bjornarsb
05-24-2007 03:19 AM
HI Jeff,
Use Prefix-list / Distribution-list when routing limited subnets in some protocols
distribution list:
access-list 10 permit 10.1.1.0 255.0.0.0
access-list 10 deny any
router bgp
distribution list 10 out/in
Prefix-list is also an better option for filtering.
Pls Rate if Helps ! !
Best Regards,
Guru Prasad R
05-24-2007 02:47 PM
Change your ACL to prefix list.
ip prefix-list ABC seq 5 permit 10.10.10.0/24
ip prefix-list ABC seq 10 permit 10.20.10.0/24
ip prefix-list ABC seq 20 permit 10.30.10.0/24
ip prefix-list ABC seq 30 permit 10.40.10.0/24
ip prefix-list ABC seq 40 permit 10.50.10.0/24
Then change your route-map to prefix-list to.
route-map Out permit 5
match ip address prefix-list ABC
HTH,
John
05-24-2007 04:47 PM
Spare yourself the time in writing a long ACL if you have SEVERAL networks by using the command below. Thats only if the prefix-list may end up to be long... this may be easier.
ip prefix-list MYLIST seq 5 permit 10.0.0.0/8 ge 24 le 24
or
ip prefix-list MYLIST seq 5 permit 192.168.0.0/16 ge 24 le 24
05-25-2007 06:26 PM
Hi guys,
Using ip prefix-list works on my advertisement. I tried redistributing my bgp routes to eigrp for my internal network to see the internet, it doesnt seem to work. How will my network on RouterC learn routes from my bgp?
tnx.
05-25-2007 07:24 PM
Hi guys,
My redistribution is working right now. When redistributing learned routes from bgp, can i see them on my routing table? I tried sh ip route on my router C and i cant see them.
tnx.
05-26-2007 12:18 AM
Hi Jeff,
I am glade that you have it working, when showing the ip route on a router doing redistribution the routes shall appear belonging to the original protocol, not the protocol that they are redistributed into.
HTH, please do rate all helpful replies using the scroll box on the right,
Mohammed Mahmoud.
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