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Is this a good solution? Please verify BGP multihome configuration with load sharing.

Posted on 2004-04-01
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Last Modified: 2006-11-17
BGP experts, I have done quite a bit of research and come up with the below listed configuration. I will be multihoming with 2 ISP's and load sharing inbound and outbound.
Please verify that my configuration will :
1)aggregate routes properly.
2)Load share effectively across the 2 links.
3)Provide redundancy if 1 link should fail.

router bgp 300
 network 208.186.228.0 mask 255.255.255.0
 network 208.186.228.128 mask 255.255.255.128
 network 208.186.153.0 mask 255.255.255.0
 network 208.186.153.128 mask 255.255.255.128
 network 209.63.53.0 mask 255.255.255.0
 network 209.63.53.128 mask 255.255.225.128
 neighbor 10.10.10.10 remote-as 100
 neighbor 10.10.10.10 prefix-list firsthalf228 out  
 neighbor 10.10.10.10 prefix-list firsthalf153 out
 neighbor 10.10.10.10 prefix-list firsthalf053 out
 neighbor 10.10.10.10 prefix-list default in
 neighbor 20.20.20.20 remote-as 200
 neighbor 20.20.20.20 prefix-list secondhalf228 out
 neighbor 20.20.20.20 prefix-list secondhalf153 out
 neighbor 20.20.20.20 prefix-list secondhalf053 out
 neighbor 20.20.20.20 prefix-list default in

 ip prefix-list default seq 5 permit 0.0.0.0/0
 ip prefix-list firsthalf228 permit 208.186.228.0/25
 ip prefix-list firsthalf228 permit 208.186.228.0/24
 ip prefix-list firsthalf153 permit 208.186.153.0/25
 ip prefix-list firsthalf153 permit 208.186.153.0/24
 ip prefix-list firsthalf053 permit 209.63.53.0/25
 ip prefix-list firsthalf053 permit 209.63.53.0/24

 ip prefix-list secondhalf228 permit 208.186.228.128/25
 ip prefix-list secondhalf228 permit 208.186.228.0/24
 ip prefix-list secondhalf153 permit 208.186.153.128/25
 ip prefix-list secondhalf153 permit 208.186.153.0/24
 ip prefix-list secondhalf053 permit 209.63.53.128/25
 ip prefix-list secondhalf053 permit 209.63.53.0/24







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Question by:msprinkle
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Expert Comment

by:Scotty_cisco
ID: 10735597
Maybe I am a little confused... but why in your BGP are you advertising entire class C address ranges and then following up with a /25 ??? not only that ... are you running BGP to your internal network?  and recieving up dates for your private network from the LAN?  If not why the Prefix lists?

... Is this all on the same router? or are you going to use 2....

This will work if you are using one router and you either define the prefix-list default in for all routes or you just remove it completely... you only want a prefix list in if you do not want to recieve the entire internet routing table and even then most of the isp's will filter them for you if you want.  

Thanks
scott
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LVL 12

Expert Comment

by:Scotty_cisco
ID: 10735636
Never mind on the prefix list about the outbound ... doh ISP 1 does not want to see ISP 2's routes and vise versa... but everything else is pretty much accurate...
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Author Comment

by:msprinkle
ID: 10735847
Yes this will be on one router.
Should I remove the /25's that I am advertising?
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LVL 12

Expert Comment

by:Scotty_cisco
ID: 10735985
I would ... because you are already advertising the /24 and that should cover all ; unless you have the network subnetted somewhere?

This would work fine for what you suggest then..

Thanks
Scott
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Author Comment

by:msprinkle
ID: 10736181
I will advertise only the /24 and let the prefix lists filter the outbound routes to the appropriate isp.
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Expert Comment

by:Scotty_cisco
ID: 10736226
On the inbound you should not need those prefix lists.. how much memory does your router have??? 256Mb you will have no problems.
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Author Comment

by:msprinkle
ID: 10736256
Its a 3640 with 128mb of memory. I want to make sure and recieve only default routes, an internet routing table will take my router down.
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Accepted Solution

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Scotty_cisco earned 500 total points
ID: 10736274
have you told your ISP to only give you those ?  or filter based on your isp's AS number?  then you should get a fairly small routing table...

Thanks
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Author Comment

by:msprinkle
ID: 10736303
I have told them to send me default routes only, I put the filters in place in case they screw up.
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Expert Comment

by:Scotty_cisco
ID: 10736316
Not a bad Idea had that happen before thanks
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