So now we're going to look at the case of two upstream providers and we'll keep one local peer in here to keep the examples complete. It could be a single local peer could be internet exchange part and we've covered those scenarios and the examples up to now we want to focus on the two up streams when we connect to both upstream providers to see the Internet so we get external redundancy and diversity the whole reason why we want to multi-home as we covered at the start of this series and we connect to the local peers that local traffic stays local of course so let's look at the diagram we now have a s 100 connecting to s 120 the local peer and connecting to two up streams a s 130 and a s 140 notice we have three external facing Rattlers remember the peering router should not be carrying default route or the full BGP table so we don't want to connect the local peer to the same router we connect an upstream provider to a notice we keep the upstream provider router separate as well it's the whole redundancy question again if we connected to up streams to the same router and we lost the router we lose both up streams so the minimum number in this example is three routers being required to configure this we announced a slash 90 negra gate on each link we accept the default router only from the app streams except all routes originated by the local peer the configurations are the same as we saw earlier router a's configuration is the same as in previous examples except what they originated announced to them what we originated router c configuration we accept the default then we send the aggregate out router d configuration to the other upstream default in aggregate out by simple configuration though it's not very useful i it works but traffic to the to upstreams will simply be nearest exit as we've seen before. What we want to try and do now is make the loadsharing much better and the better configuration options available well we could do full routing from both app streams that seems to be the favorite of many today but the other way and probably the better way is to accept the default from one upstream and some routes from the other upstream and we're going to look at these two cases now to show you and compare them so that you can make a choice.
© Produced by Philip Smith and the Network Startup Resource Center, through the University of Oregon.
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