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Community Member

more on routing

hi all,

i got some help a week or so ago on how to get a back-up internet site working with bgp. as far as the wan goes, i understand how to tell everyone that the backup site is to be used if the main link goes down. next question:

Set up and follows:

internet

|

CE1 - - PE1- - - -PE2 - - -CE2

|

|

CE3- - internet

say the back-up site(ce3) has to be used. do i need a second default route on the ce3 site router pointing towards the internet router connected to that lan? i obviously do, but I was just curious about how to handle this. should i just have a second default route with a higher AD?

TIA,

R

6 REPLIES
Purple

Re: more on routing

Hi,

As far as CE3 goes, would it not be preferable to get hosts connected to CE3 to use the local Internet link ? The other sites can use CE3 as a backup but local sites can use the closest Internet connection. If you choose to do so, configure the default route on CE3 with the default AD (0). If you want even CE3 hosts to use the main internet link, then use an AD such as 250 on it.

Hope that helps - pls rate the post if it does.

Paresh

Cisco Employee

Re: more on routing

You definitely need a default route on CE3 pointing at the Internet router. How is the primary default route learnt on CE3?

Thanks,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Community Member

Re: more on routing

Thanks to both of you, again!

I have heard good and bad about allowing the local users to CE3 access the internet link, one with being price, lol. But would this be the best thing to do? Would it complicate my bgp config? or just a matter of the default routes being different? i think we wanted everyone to come here also for internet filtering.

The default route on CE3 is done by static route. It is participating in BGP with the PE router from my service provider to let the PE routers know that it is the back-up internet route.

Purple

Re: more on routing

It may come down to commercials... if you are paying for the link on a usage basis, then by all means, get the users on CE3 to use the primary link at CE1. If not, then just use the local link. Either way will work.

Case 1: CE3 users use local link

If a default static (AD 0) is present all CE3 users will use that link. If that link goes down, the default will be removed and CE3 users will use the default learned bia eBGP.

Case 2: CE3 users use remote link

The default will have a high AD so the default route used will be the one learned via eBGP. If that is lost for some reason, the static default will kick in.

Hope that helps - pls rate the post if it does.

Paresh

Community Member

Re: more on routing

just to clarify, i will have the following correct? or do i not need the first as BGP will be supplying for me? (if using case 2)

ip route 0.0.0.0 0.0.0.0

ip route 0.0.0.0 0.0.0.0 250

Cisco Employee

Re: more on routing

If you receive the default via BGP from the PE then you don't need the first static route.

The floating static route will kick in as soon as you loose the default received from the PE via BGP.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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