BGP reconfiguration

hitman0577

Hello,

I need some advice on BGP. My company's network is comprised of an complete class C ip address and divided into two subnets. We are are using the second subnet. We are using two providers but want to get rid of one them.
We are using BGP-4 and one autonomous system number that exchange routing information with both providers.

The question:

If we were to eliminate one of the provider and go with a new ISP, would we have to keep the class C address as is and the ip addresses from that provider, or would we be able to just eliminate the provider and use just a fraction of another class C using a .192 subnet instead of the .128 we are using now?

Any suggestion will be appreciated.

My boss is on my case about this because I am CCNA certified and not able to come up with a quick response to this here dilema.

Thanks

Hitman

keenon

they expect the world from you sounds like a great opportunity to ask for more training..lol

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml

heres something that may help

other thing are you accepting bgp updates in from ISPs or just using them as the default route.

hitman0577

We are accepting updates from the ISPs.
Here is part of the current configuration:

router bgp 32439
no synchronization
bgp log-neighbor-changes
bgp dampening
redistribute static route-map primus
neighbor 66.181.95.185 remote-as 17054
neighbor 66.181.95.185 description Expedient (AS17054)
neighbor 66.181.95.185 update-source FastEthernet1/0
neighbor 66.181.95.185 soft-reconfiguration inbound
neighbor 66.181.95.185 filter-list 1 in
neighbor 66.181.95.185 filter-list 2 out
neighbor 66.181.95.186 remote-as 17054
neighbor 66.181.95.186 description Expedient (AS17054)
neighbor 66.181.95.186 update-source FastEthernet1/0
neighbor 66.181.95.186 soft-reconfiguration inbound
neighbor 66.181.95.186 filter-list 1 in
neighbor 66.181.95.186 filter-list 2 out
neighbor 209.58.194.117 remote-as 7203
neighbor 209.58.194.117 description Primus
neighbor 209.58.194.117 update-source GigabitEthernet0/1
neighbor 209.58.194.117 soft-reconfiguration inbound
neighbor 209.58.194.117 filter-list 1 in
neighbor 209.58.194.117 filter-list 2 out
no auto-summary
!
ip classless
ip route 207.244.119.0 255.255.255.0 Null0
ip route 207.244.119.0 255.255.255.128 207.244.119.204
!
ip as-path access-list 1 permit .*
ip as-path access-list 2 permit ^$

The link you sent showed me some really nice sample configurations, but my question still remains:

Does it matter whether I use a fraction of a class C address for this BGP config and use only 255.255.255.192 subnet mask, or do I have to use the whole class C address?

We have another set of ip addresses available that we want to use for when we get rid of this Primus ISP, but instead of using the .128 subnet we want to use a .192 subnet.

I hope that is not too much information.
!

keenon

i think it will be fine.. their will be some configuration that will be required i'm not sure on whos end either the ISP or both of yours. also with you accepting updates from isps it will advertise the other isp through your AS which is not good. but someone that has more experience with bgp configurations should be able to provide better help.

darkuser

depends WHO owns the subnet(s) you're using.
and How You're using them.
what you are advertising.... and where and to whom.
do you receive full or partial routes ?
or just a default ?

unless you've been allocated ip's directly from arin you don't own any ip address space , you're just renting them from an isp.

isp's don't like cancellation and take pleasure in watching you suffer from renumbering. a nat based renumbering strategy usually works.

it appears 207.244.119.0 is primus address space
if you cancel them they'll want it back.

the smallest direct allocation you can get from arin is /20.
i know .. i have one .
if you're needs are smaller than that you have to live at the bekon call of your isp dejure.

rossonieri#1

darkuser has answered all of your Qs...

even you use a class C subnet - was it public? from which isp do you rent it from? and if you would like to cut off their connection -> then you probably have to re-numbered your net.