Under the bgp process on your headend router, you could put "neighbor default-originate". Clear the neighborship and you'll send a default to the ISP. The ISP will then in turn send to your remote sites. (If there are any filters.)
** Edit **
You'll want to make sure that you have a default route on the headend router pointing toward the internet though.
Yes there is an existing default route towards the Internet - the route points to the Core switches and from the Core switches to the Firewall.
So, the headend will still see a default route to the Cores after making this change? And the Service provider will then have a default route to our headend? And should be able to forward unknown routes accordingly?
I wanted to make sure I let you know that if you have static routes now for the default gateway on your remote sites, those will be preferred over your bgp routes. When you advertise your default from the headend router, go to one of the remote routers and do a "sh ip bgp 0.0.0.0". You should see a route that's bgp learned pointing to your ISP. Once you have that, it should be safe to remove the static if you're wanting to do that.
I would also recommend that when you remove the default route on one of the remotes, if you don't have a full view of your network and depend on default routes to get you everywhere, I would set the router to reload in case you remove the static and something happens with the bgp learned default route. In other words, if for some reason you remove the static default route and lose connection to the network, you can have a backout plan with a reload. Do a "reload in " before you remove your static route. If you remove the static and lose connection to the router, the router will reload in however many minutes you specify with the old configuration. If everything goes well, you can cancel the reload with "reload cancel". These commands are done at the enable prompt and not global config.
I will try it on one our sites that actually has a down time first with the reload command.
Couple more questions:
If there is an existing default route to the Headend configured on the remote router, will configuring the "neighbor default-originate" and "clear ip bgp * soft" on the headend cause any temporary disconnects?
I currently have 2 default routes configured on the remote routers pointing to the provider. One is for the primary link and it has the default cost. The other is for the backup T1 link which is also using eBGP and it has a configured cost of 254 so the primary is preferred.
After I confirm the BGP default route is being advertised to the remote router from the ISP and after I delete the primary default route, will the ISP default route be preferred? I don't want my T1 route to be used unless the primary goes down.
On the other side of the remote routers are layer 3 switches that have a default route pointing to the remote router. I can leave that config, correct?
When you advertise the default to the provider, the remote will learn the default route and it will still point to the provider. Your static route will stay in the routing table though since the ebgp learned route will have an AD of 20. There shouldn't be an outage that I can see. If you do a soft clear, you shouldn't have any interruptions, although to be on the safe side I'd do this config after hours. Another thing that you could do, if you already have a static route on the headend router, is to advertise that route under your headend bgp process with "network 0.0.0.0". Then you wouldn't have to clear the bgp sessions.
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