[AusNOG] Influencing Routes

[Phillip Grasso]

You'll need to think about prefix symmetry (is it ingress or egress or
both). Is intended destination x.x.x.a/24 or is that the route your
advertising.

If your making changes just be aware that you might be impact all your ASN
traffic unless doing using the special knobs.

Generally suggestions using as-path to impact inbound is prone to problems
- especially around other providers controlling their own localpref.

If want to sure up ingress path, use longer prefixes and summarization. (So
long as your prefixes shorter or equal to /24.

Egress control is generally easier with use of local pref polices.
On 26/02/2015 7:17 pm, "Damien Gardner Jnr" <rendrag at rendrag.net> wrote:

> It's not so much the 'hops' as far as traceroute hops - it's (usually)
> purely based on AS-path.   There could be far more actual hops in the
> 'shorter' bgp path, and it'd still take that path, as there's less AS
> numbers in the path.
>
> I've recently brought up a BGP session in the US, and run
> ipip/ipip6/ip6ip/ip6ip6 tunnels from my US router back to my provider IP's
> for each of my upstreams.  A little overkill, but means I'd have to lose v4
> AND v6 on both upstreams, to lose international connectivity.  I then
> established an iBGP session across each tunnel from Syd to Lax (with
> localpref munging to force traffic over my cheaper upstream), and my all my
> IP's get advertised from both locations.
>
> Though I'm more interested in the Sydney IP's being reachable from Lax,
> than the other way round, so if bandwidth becomes an issue, I'll be
> de-advertising the Lax-based /24 from sydney  You need to be aware of how
> much traffic your US subnet is doing, as you'll now be paying to pull that
> INTO Sydney, and then back out over your tunnel.  Depending on your
> upstreams, you may have to add a prepend or two on your provider sessions
> in Sydney to make sure US traffic comes in your tunnel, if your provider
> also peers in the US.
>
> HTH
> .
>
> On 26 February 2015 at 18:17, Daniel <daniel at dwatson.me> wrote:
>
>> Gday Guys
>>
>> Thanks for the responses thus far,
>>
>> So I should keep the BGP to my LAX provider, and also establish another
>> one
>> back to AU and announce it through my Sydney provider?  So theortically it
>> will be a shorter path into Sydney > GRE > LAX Router   then over the SCC
>> and a heap of extra hops
>>
>> Is that correct?
>>
>> Daniel
>>
>> -----Original Message-----
>> From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Ben
>> Sent: Thursday, 26 February 2015 5:59 PM
>> To: Daniel
>> Cc: ausnog at lists.ausnog.net
>> Subject: Re: [AusNOG] Influencing Routes
>>
>> easist solution is to just run BGP on the GRE tunnel assuming you're
>> advertising PI space in both locations.  advertise the /24 over the
>> tunnel.
>>
>> if the /24 is owned by the LA overseas provider you'd have to ask them for
>> permission to readvertise, and for them to advertise it as a /24.
>>
>> Ben.
>>
>> On Thu, Feb 26, 2015 at 02:16:18PM +1100, Daniel wrote:
>> >    Hi Guys
>> >
>> >
>> >
>> >    I have a network related question that I would love some input from
>> you
>> >    on,
>> >
>> >
>> >
>> >    Say ive got a network x.x.x.a/24 advertised in LA,  and I have a
>> GRE/EoIP
>> >    setup between my network in Sydney and LA,
>> >
>> >
>> >
>> >    Is there any way I could force traffic for x.x.x.a/24 into my Sydney
>> >    network and then push it overseas via said tunnel? Instead of the
>> default
>> >    route table listing which would take it via (For example) TPG > AAPT
>> >
>> >    Vocus Sydney > Vocus San Jose > HE > NTT > GloVine > SERVER
>> >
>> >
>> >
>> >    Any questions please feel free either on or off-list
>> >
>> >
>> >
>> >    Daniel
>>
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>>
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>
>
>
> --
>
> Damien Gardner Jnr
> VK2TDG. Dip EE. GradIEAust
> rendrag at rendrag.net -  http://www.rendrag.net/
> --
> We rode on the winds of the rising storm,
>  We ran to the sounds of thunder.
> We danced among the lightning bolts,
>  and tore the world asunder
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