[c-nsp] Multihoming

Jason Berenson jberenson at vinylinteractive.com
Mon Aug 31 18:50:52 EDT 2015


You're right, a 4-byte ASN on the 3560's won't work.  I might see if 
ARIN will reassign me a 2-byte ASN instead.  If not, I'll have to go 
with something like a 28XX software based router and a pair of 2960G's 
for switches.  I was just hoping to do it all in two boxes instead of 4.

My plan is to have ports in front of the firewalls as well as ports 
behind the firewall.  I'll also create a separate VLAN for internal (non 
routed traffic only) between hosts but might just use another switch for 

We may not have the same bandwidth from both providers, if we do then 
letting BGP decide would be fine, I think.


On 8/31/15 1:43 PM, Justin M. Streiner wrote:
> On Mon, 31 Aug 2015, Jason Berenson wrote:
>> Was interested in getting any pointers anyone might have about multihoming.
>> I've got an ASN and am working on a /24 from ARIN now.  I was thinking about
>> a pair of Cisco 3560's one for each provider and I was going to take default
>> routes from each, one with a higher metric and announce my prefix over the
>> primary link and pad the secondary link.  No customer or full tables needed.
>> I was thinking about vlan'ing each switch into half public half private side
>> also.  Any pointers or tips or recommendations would be greatly appreciated.
>> It's been a while since doing this type of stuff.
> You might need to get your IPv4 space from one of your upstream providers.
> As far as ARIN is concerned, that well is dry.
> You will also want to start giving serious thought to IPv6.
> I don't know how well 3560s handle BGP, but if you're just taking default
> routes from your upstreams, the resource needs are pretty light.  As the
> other person who responded mentioned - 4-byte ASNs could be an issue as
> well.
> You can accept the default route from provider A with a default
> local-preference and the one from provider B with a lower local-pref.  For
> outbound advertisements, as you mentioned, you can prepend your AS a few
> times on your announcement to provider B.  You'll also want to run IBGP
> between the two 3560s.
> When you say "half public, half private", can you clarify what you're
> trying to do?
> jms

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