[c-nsp] Multihoming

Reuben Farrelly reuben-cisco-nsp at reub.net
Mon Aug 31 18:34:34 EDT 2015

On 1/09/2015 6:43 AM, 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.

3560's handle 4 byte ASNs just fine provided:

- You have sufficient flash.  4 byte ASN support in the Catalyst 
platforms was introduced in 15.2(1)E so this is the absolute minimum 
version you will need to run - and this image (in fact anything newer 
than 12.2(55)SE) requires 32M flash.

- You have the IPSERVICES image/license as BGP is not supported in IPBASE.

As you're only handling a handful of prefixes if you meet the 
requirements above you should be fine.


More information about the cisco-nsp mailing list